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Forward modelling and inversion with 3D GeoModeller

1. Standard deviation Statistical law Normal Percentage of Population 000 0 25 050 075 100 1 25 150 175 200 225 250 275 300 325 350 375 400 Density Mode 1 Mode 2 2 Help of OK l X Cancel Rock Property Law Popup in 3D GeoModeller Note in this case there are two modes for this proposal density distribution low 20 of 3 4 g cc and 80 of 2 67 g cc The syntax shown in the Description panel has Normal 3 4 0 2 20 Normal 2 67 0 0 80 the first parameter is the mean density the second the stndard deviation and the third is the percentage of the population following this law Figure 5 This shows a completed table of rock property values from a project 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 20 Contents Help Top lt 4 Back gt being reported upon as one of a study s deliverables Density and magnetic properties oom foom f omm T aerae oneto Newer Volcanics Logomal EnidounGrnne Lognomal Black Borom puton Logvomal Moum Lonarcn Ganie LogNomal JEJE je exton Granodbme Lognomal Natte Yalock Granie inner Logvoma Natte Yalock Grane Outer LogNornal J catenaneco nomar 270 oes rooma s 2 nomai 270 0005 wgomat Dja Dp Wrang Supergroup Normal 281 0 010 LogNomal 10 Ambient magnetic 60117 nT inclination 6
2. gives rise to probBack values equal to the number of voxels in the face neighborhood equal to the old lithology divided by 6 and probForward values equal to the number of voxels in the face neighborhood equal to the new lithology divided by 6 Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 118 Contents Help Top lt 4 Back gt Recommended Shape Ratio Settings Contents Help Top There are times when you could conceive of modeling a geological body in a manner that you know is much smoother than what is normally observed in nature As an example imagine a scenario of modeling a granite intrusion as a smooth sphere In this case you can allow a shape ratio law of say 0 2 0 05 By setting the first parameter to a non zero value you acknowledge that real geology is rougher than how it has been modeled Mostly however it is recommended that the first parameter is 0 0 and the second is close to 0 05 to 0 1 In the current implementation we are dealing with voxets so some of the above discussion has to be modified to take that reality into account For every single protruding voxel the added volume is 1 and the surface area has 4 added to it For very recessed voxel the volume actually decreases by 1 but the surface area has 4 added to it Atypical Shape value for a unit with lots of surface roughness would be gt 3 0 For v
3. 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 14 Contents Help Top lt 4 Back gt Taking this 3D geology model as a starting position you now have the option to test your model against independently observed geophysical datasets These are typically gravity and aeromagnetics A lithological constrained inversion needs to honour all facts and then explore those aspects of the model that are uncertain to see if a better fit to the geophysics can be found It is this case that 3D GeoModeller concentrates on In the inversion context the geological facts are defined to be not only the original observed contacts but also some aspects of the 3D volumes that are created Currently faults dykes and structural dip and strikes are not honoured in the directly inversion process Seperate dyke modelling and inversion is available Several viable geophysical techniques are routinely used to help you gain answers to solving aspects of your undercover geology The following diagam illustrates the use of differing geophysical approaches that are in common use You can see we propose that the new technology developed in 3D GeoModeller fits at the end of the spectrum where you already know quite a bit about your context Figure 2 3D maps supported 3D maps supported by the geological by the magnetic observations observations 3D maps supported by the gravity shir produc
4. GeoModeller User Manual Conients Help Top 6 q Back gt tools and techniques described in this reference manual Basically any standard industry lithology voxet can be used Mostly there is a need for a regular 3D grid but this is not an architectural requirement as Geomodeller is moving to using tetrahedral mesh representations of the geology as one of its outputs i Explore 5 testArea_2suites_imported testArea_2suites_imported xml S g Formations F Dykes H rauts H BM Sections i Drilholes 30 Geology Wp Grids and morhan i Meshes and grids No meshes or grids U Create grid with zero value field lmj W aa HORIZONTAL 3D Grid Voxels Triangulation 2D or 3D Observations ASCI 2D or 3D Observations 2D Grid D Ok The link between the lithology key and a formation name has to be established The convention is to assume that the lithology is stored as an integer number and each number corresponds to a formation The property of the lithology voxet Right mouse button bottom of list should show this field having the alias set to Lithology amp Explore Manage MeshGrid Field Properties Name Lithology Units Lithology Description 3 Q testArea_2suites_imported testArea_2suites_imported xml H g Formations oves H Fouts H j Sections I Drillholes 20 Geology 5 p Grids and meshes S BY ThermalProducts Af Litholops 14 14 Front
5. MakeSurface Shells Iso surface shells Image backdrop Movie of model shown for section on sequential vertical evenly spaced sections MakeDenvedVoxet MakeHistogram Property MakeSectionMovie histograms Profile plots Observed of geophysics Inversion 3D GeoModeller inversion flowchart showing the main persistent data objects and the Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd lt 4 Back gt GeoModeller User Manual 32 Contents Help Top 4 Back gt executable commands used to generate inversion results and reports Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 33 Contents Help Top lt 4 Back gt Support for Full Tensor Gradiometry Falcon Contents Help Top 3D GeoModeller can make use of any of the measured scalar vector components and second order tensor gradients of a potential field A predicted response from your model of a full tensor signal at an average elevation above the topography can be made Support for magnetic remanence in any of the geological units is also given and this can be made to influence the forward model The Forward Model FFT option generates a genuine tensor grid rapidly The Results viewer in the case of tensor data shows one of the magnitude measures Cube Root of the Second Invariant of the tensor curvatures You must use the ERMapper gri
6. b Ensure the voxel can be changed eg Nota fixed cell c Make the change nb Lithology change will only be to a frontier cell Is the proposed litho model acceptable Passing all geology tests against the reference voxet geology model yYES Randomly and independently resample each property for the voxel Select next geophysical dataset Yy using order of supplied grids Forward model the relevant property field and match polynomial trends between calculated and observed grids if appropriate Calculate the likelihood for the proposal Lp NO ae of Run NO YES p Proposed model is more likely than the current model Lp gt Lc Obtain random marker from equi probable distribution 0 1 Pr Pr lt Lp Le YES NO Tested each geophysical dataset ae T YES A Accept the proposal and update current model v YES number o reached More proposals to YES NO consider NO Return 3y 105 lt 4 Back gt Scheme to test and apply proposals including property resampling the case where you change the physical properties Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd lt 4 Back gt GeoModeller User Manual 106 Contents Help Top lt 4 Back gt RunControl Parameters Number Of Iterations Although the one
7. Advanced Tuning Seed 1234 Random Large misfit RMS threshold factor L Large misfit temperature L Allow dual temperature mode Mode 1 Temperature factor Entropy 1 Duration 100 Temperature factor 1000000 Duration 99900 l Mode 2 SetLargeMisfitRMSThresholdFactor SetLargeMisfitRMSThresholdFactor is a parameter that is used during the initial stages of an inversion run allowing the user to adjust the likelihood function used in the geophysical data acceptance tests SetLargeMisfitTemperature SetLargeMisfitTemperature is another startup parameter allowing the user to adjust the likelihood function used in the acceptance tests The default is one If the misfit of the proposed model is greater than the standard deviation assigned to this geophysical data type multiplied by the SetLargeMisfitRMSThresholdFactor value the variance for this geophysical data type is multiplied by the value of SetLargeMisfitTemperature This has the effect of modifying the probability of acceptance A temperature value less than 1 decreases the probability of acceptance for a given misfit value This tends to force a steepest descent behavior to the Run with proposals being accepted only in the situation where the misfit decreases at least until the misfit equals the product of the standard deviation assigned to this geophysical data type and the SetLargeMisfitRMSThresholdFactor value
8. Change Count Property 2 Mean Density Property 3 Std Dev Density Property 4 Most Probable Property 5 Most Probable Thresholded Property 6 probability Unit 0 Property 7 probability Unit 1 Property 8 probability Unit 2 Property 9 probability Unit 3 Property 10 probability Unit 4 Property 11 probability Unit 5 Property 12 probability Unit 6 Comments Change count is the number of times this particular voxet has had a change Mean Density is the average density that has evolved from all the inversion testing for this voxet Std Dev Density is the standard deviation for this mean density property Property 4 This contains the Most probable means Report for each voxet location the lithology used for the majority of the total number of proposals Report back the location and lithology of those voxets This field shows the majority wins request for all voxels and so will always have a lithology result Property 5 This contains the Most probable thresholded means Note Property 5 is the only one that changes from changing the probability threshold all others reported fields are identical The number reported is derived from considering all of the accepted proposed geology models For those models report back all the voxets which remain a single lithology for a given percentage or more of the total number of proposals Report back the location and lithology of those voxets Figure 27 Black vol
9. Continue Yes 13 No Exploration Run Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 17 Contents Help Top lt 4 Back gt Statistical presentation of inversion simulation outcomes Using this procedure it is possible to generate a large number of linked models that reproduce the gravity and magnetic observations to an acceptable degree These can then be analysed and combined statistically For an inversion example the most probable lithology above a specified threshold can be computed from the many stored models and presented as one statistical model Similarly for a heat study a parametric sweep through permutations of properties and boundary conditions also results in many linked models that reproduce the downhole temperature gradients surface temperatures but also show the variability of heat flow and temperatures at greater depths Advantages of joint geophysical inversion Tensors and causative bodies Each independently observed geophysical dataset can add something of value to helping to validate your 3D geological model The laws of physics are at work with these natural manifestations Gravitational effects from a density contrast between geological units a simple contact falls off by a square root of distance rule Induced magnetic effects at a susceptibility contrast junction or edge in your model falls off as the cube
10. GeoModeller User Manual 29 Conients Help Top Contents Help Top 4 Back gt Heat Uncertainity Studies With this release comes the capability to do parameter uncertainty studies The following is a screen shot after one of these studies relating geology heat flow heat production from buried granites that are radiogenic The aim here is to constrain the likely temperatures at depth given all the knowledge of rock properties and geology setting The way of doing these types of uncertainty studies has been termed a parameter sweep You specify which of the boundary conditions and rock units variables in play have an uncertainty that is most likely to influence the predicted outcomes You then select if you want 2 or 3 variations for each of these variables eg minimum mean maximum For instance if there are 5 variables either 32 or 217 cases are defined These can be run in parallel as they are all unrelated and when all the simulations are complete a staticical analysis and compilations can be made in the 3D model space to form a view about the overall varaibility that you are likely to see 1 900 1 800 1 700 1 600 1 500 1 400 540000 1 300 Asc o000 1 200 1 100 1 000 Stddev_Temp S900000 g4 0000 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 30 Conients Help Top q Back gt Definitions and Management of Workflow Scenarios
11. N Reference R Lane GA Ray Seikel IG Antonio Guillen IG BRGM VAINTREPID HYSI Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd lt 4 Back gt GeoModeller User Manual 76 Contents Help Top lt 4 Back gt ForwardModelFromProject RUN The ForwardModelFromProject command computes the geophysical responses of a 3D GeoModeller Project The required computation task is partly specified by the supplied command line parameters and partly from the various properties of the 3D GeoModeller Project details below Forward Model Wizard Potential Fields 3D The wizard makes it easier for the user to select the correct modelling parameters In the first wizard panel you can choose the name of your forward model and check the components that you would like to compute It is also possible to clone a case i e reuse the parameters from a previous modelling run The second panel lets you choose an observed grid for the component you want to calculate and determines the surface where you want to calculate the model The field under the From External Resource box lets you choose a band if your input grids has multiple bands You can safely ignore it if your just working with a regular grid You can calculate the model response on a constant elevation this is a real elevation not a clearance from the highest topographic point or similar or you can use a drape surface
12. Two terms that are used throughout this document are Case and Run Case combines the a priori information with the observed data and is thus a geological or geophysical hypothesis or scenario which we propose to test It is a geological model together with knowledge of the physical properties of the geology formations and it is also a set of geophysical gravity magnetics datasets and such auxiliary data as the definition of the Earth s magnetic field parameters for the particular project area Run an actual execution of a 3D GeoModeller process based on a particular Case For a given geological or geophysical scenario there are many ways that a Run might be executed by setting controls that constrain the way in which an inversion or simulation can proceed Thus a Run contains the specifications of all Run control parameters and also the full set of results from the Run Results are primarily the complete set of proposed changes to the geology model that were accepted during the particular Run There may be one or more Runs associated with an inversion Case A Case and one or more associated Runs are represented symbolically in Figure 9 Other terms used extensively in this document are Contents Help Top Project is a 3D GeoModeller Project A Case contains a copy of a 3D GeoModeller Project The 3D GeoModeller geological model must have been computed the inversion derives the geology voxel model from the computed mode
13. e lt PropertyLaw gt The parameters defines the statistical distribution of property values in terms of a statistical law distribution and its associated parameters Each formation can be described in terms of a single lithology uni modal distribution or a mixture of up to three component lithologies bi modal or tri modal For a uni modal distribution lt PropertyLaw gt has the following syntax message ProbabilityDistributionFunction_GMT required ProbabilityLawType type lt I YPE gt default Normal optional double mean lt MEAN gt default 0 0 optional double stddev lt STDDEV gt default 0 0 optional double inclination lt INCLIN gt default 0 0 optional double declination lt DECLIN gt default 0 0 optional int32 percentage lt PERCENT gt default 100 optional string input_voxet lt VOXET gt take a predefined external property voxet distribution optional string input_voxet_field lt FIELD gt field to use in that voxet optional string input_grid 9 where lt TYPE gt The type or style of the Probability Distribution Function PDF The Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 62 Contents Help Top lt 4 Back gt usual Gaussian or Normal Log Normal Poisson Rayleigh Weibull are available A Uniform style meaning a constant is also available lt MEAN gt The mean of the P
14. type type type type type type LithologyProperty lithology Air property CommonalityVolume ProbabilityDistributionFunction Normal mean 0 00 stddev 0 LithologyProperty lithology Water property CommonalityVolume ProbabilityDistributionFunction Normal mean 0 00 stddev 0 LithologyProperty lithology SedUpper property CommonalityVolume ProbabilityDistributionFunction Normal mean 0 00 stddev 0 LithologyProperty lithology SedMiddle property CommonalityVolume ProbabilityDistributionFunction Normal mean 0 00 stddev 0 LithologyProperty lithology SedLower property CommonalityVolume ProbabilityDistributionFunction Normal mean 0 00 stddev 0 LithologyProperty lithology Basement property CommonalityVolume ProbabilityDistributionFunction Normal mean 0 00 stddev 0 LithologyProperty lithology Mantle property CommonalityVolume ProbabilityDistributionFunction Normal mean 0 00 stddev 0 If we define SameQ to be the number of voxels in the intersection of the lithological regions for the jth formation between the reference and the present model gain j is the number of voxels in the present model that are outside the region occupied by this formation in the reference model and loss j is the number of voxels in the reference model that are outside the region occupied by this formation in the present model then CommonalityVolume is given by
15. 1995 comment on this specifically on pp12431 12447 They point out that either approach is acceptable but that it is usually quicker to apply the Metropolis acceptance tests in cascading fashion to avoid unnecessary forward model calculations The proposal only has to fail for one of the grids to fail completely Hence forward calculations for the remaining grids become unnecessary It is also worth noting that it is advisable to specify the geophysical data types in the NewCase command in order of increasing computational complexity This makes the algorithm more efficient Gravity data types should therefore be specified before magnetic data types Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 98 Contents Help Top lt 4 Back gt Interactive Wizard for setting and running With v2012 all the functionality of the full stochastic inversion language is now accessible via the 3D Inversion wizard option Geophysics gt 3D gt Inversion Some of the pages are quite similar to the Forward Model wizard as the need to set properties and choose grids set the run environment is shared The main differences appear on pages 3 amp 4 and these roughly correspond to the CaseControl and Run Control aspects of the full language Where possible we have set defaults and hidden away as much of the complexity as we can so that the new user can get a result that ma
16. Accuracy Estimate Variable Z By selecting the Variable Z option the user can create a semi regular voxet instead of a regular voxet See image below This allows the user to define a voxet geometry where the cell size can vary with depth The cell size near the surface can be small and then after a nominated depth start to become progressively larger This gives a better resultant forward model more efficiently than by using the smaller cellsize throughout the voxet 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 24 Contents Help Top lt 4 Back gt Variable Z Resolution Setup Define the size of cells in z direction Geology Cross Section 2 000 1 500 1 000 500 100000 0 105000 0 110000 0 c Resolution of pas z of topography ne Zmax 2000 1 500 2 000 Upper dZ 200 4 amp 2 500 Boundary At o S 3 000 gt Z Resolution below topography 3 500 4 000 Lower dZ 506 022 4500 Geometric Factor 5 000 5 500 Zmin 6 000 Number of cells in z direction 8 500 7 000 Total 15 7 500 Topography part 10 8 000 100 000 101 000 102 000 103 000 104 000 105 000 106 000 107 000 108 000 109 000 110 00 Lower part 5 Easting m m LowerCover W Granite Basement M UpperCover W MiddleCover Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd
17. Associates Pty Lid 4 Back gt GeoModeller User Manual 123 Conients Help Top Contents Help Top 4 Back gt optional bool SURFACE lt SURFACE gt default false fix the surface geology map optional ctm BoundingBox box 10 set all cells within this box optional string log 17 where lt CLEAR gt clears any previously fixed voxel lithologies It sets all voxels to be free to change during the inversion lt SURFACE gt fixes the lithology of those voxels that are intersected by the topographic surface as defined in the 3D GeoModeller Project The premise is that the surface has been mapped and is therefore known and hence the lithology of the surface voxels should not change during the inversion lt XYZ_Filename gt where lt XYZ_Filename gt is the path filename of a simple ASCII text file containing a list of X Y Z coordinates space delimited with one X Y Z triplet per line The lithology of those voxels containing any of the listed coordinates will be fixed lt OBSERVED gt fixes the lithology of all voxels within which geology contact data points are recorded in the 3D GeoModeller Project lt FORMATION gt a way to fix whole geology formations eg you have good seismic control near surface lt GOODNESS gt a way to fix geology observations based upon mapping status Note that the default is that cells along the uppermost surface or those in vertical contact wi
18. By setting Drape gt Terrain clearance to 0 you will calculate the forward response at the height of the terrain If you set it to say 100 m you will calculate it at a clearance of 100 m above the terrain With the third option Drape gt Load from dataset you can load any drape surface that is used to calculate the forward response Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 77 Contents Help Top lt 4 Back gt The next panel lets you set the resolution and extent of the voxet Here you can also choose to do a spatial or FFT forward model For spatial forward modelling the z resolution of the DTM if any will be adjusted to the value given in Vertical sampling interval e g if you set it to 50 m the resampled DTM will only have values that are equal to the lowest elevation plus integer multiples of 50 m For the 3D FFT method the vertical expansion is crucial The larger this expansion factor in percent is the better the result However depending on the voxet resolution this can require huge amounts of memory For your reference the estimated memory requirements are displayed in the bottom row There is also a signal light that gives you an idea how accurate the result will be The accuracy is only a crude estimate of the real error though and is only representative for the centre of your grid The accuracy will deteriorate towards t
19. CUBE_3x3_BOTTOM in effect a random choice of the direction in which the filter will be applied N S E W up down Apply the filter to arrive at some global perturbation proposing changes to a large set of voxels representing a migration of the boundary by one voxel in a randomly selected direction Each proposed voxel change is assessed independently if any proposed voxel change is rejected then all are rejected DilationOrErosionFilter As noted above the default usage of the DilationOrErosionFilter is complex and for each repetition the structural element used is randomly selected from a set of six directional structural elements This RunControl command sets a user chosen structural element for application in the dilation or erosion processes The DilationOrErosionFilter RunControl sub task specifies whether the dilation or erosion Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 148 Contents Help Top lt 4 Back gt filter operations are performed and at what repetition rate Note that for historical reasons dilation and erosion filter operations were performed by default Since the morphological operations are not recommended you simply ignore this command and it is turned off The dilation or erode filters are typically applied at some regular interval during the inversion to regularly perform its homogenizing process and
20. Contents Help Top lt 4 Back gt For Property Susceptibility The lt StatisticalLaw gt is typically LogNormal Example Pitfield_Volc Susceptibility LogNormal 0 0001 0 00005 100 meaning that the Pitfield_Volc consists of a single lithology 100 with a log normal distribution of susceptibility values around a mean of 0 0001 SI units anda standard deviation of 0 00005 SI units Units for Susceptibility k Use SI units Ifyour susceptibility data source uses units of SI x 10 divide by 100 000 to yield susceptibility k in SI units If your susceptibility data source uses cgs units multiply by 47 to yield susceptibility k in SI units r 3 14159 approx If your susceptibility data source uses cgs units x 10 multiply by 47 1000 000 to yield susceptibility k in SI units For Property Remanence For remanence the lt StatisticalLaw gt is typically LogNormal Additional parameters are required in the lt PropertyLaw gt to describe the vector direction of the remanent magnetisation vector Law Parameters Mean1 StandardDeviation1 Pcent1 RemanentVectorInclination RemanentVectorDeclination e Example NewVolcanics Remanence LogNormal 0 4784 0 9568 100 68 5 169 2 meaning that the NewVolcanics formation is uni modal 100 with a log normal distribution of remanent magnetisation strength mean 0 4784 SI standard deviation 0 9568 SI and with the inclination of the remanent mag
21. ForwardModelTemperatureForCreateCaseFromVoxet See 3D GeoModeller Forward modelling of heat flow An example of a study showing a predicted temperature in a 3D space is shown After the simulation use the MeshGrid gt import 3D voxet option to bring the results J EBACCCC l SANDIN 275 Temperature aaay _ PORN into the main tool for viewing The statistical report of the predicted temperature Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 85 InversionTask CreateCaseFromLithologyVoxet InversionTask ForwardModelTemperatureForCreateCaseFromVoxet Contents Help Top lt 4 Back gt population is shown below 3P Histogram of Temperature general 3D gi Statistics Histogram of Temperature general 3D grid Property Value 1 100 p ctive 1 000 n Nulls jo Nulis jo 3 00 900 Min 22 Max 513 6389 800 Mean 231 4087 Geo Mean 192 3803 Std Deviation 109 4084 kurtosis 0 8008 Skewness 0 2412 Variance 11970 1887 2 25 Mean 231 4087 Sigma 109 4065 Pr Temperature N A 8 8 2 8 SUONENaSqo Jo JeqUINN 200 o 50 100 150 200 250 300 350 400 460 500 Temperature The syntax to define a process to run simulations by batch is simple and easy to understand and change As we use the Google protobuf technology all mistakes are well reported a
22. If the appropriate standard deviation Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 110 Conients Help Top Contents Help Top q Back gt values have been specified for the Case this is unnecessary and undesirable SetDualTemperatureMode The Dual Temperature Mode allows the user to alternate between two temperatures of the likelihood function used in acceptance tests What we have here is a means of accelerating the convergence of the initial burn in period of the inversion while seeking a minimum misfit The default is false SetDualTemperatureMode lt 0 1 gt mode1TemperatureF actor mode1Duration mode2TemperatureFactor mode2Duration Where the notation indicates optional arguments If the DualTemperatureMode is set to true then the likelihood function will run at a temperature of lt model1TemperatureFactor gt for the first lt modelDuration gt iterations and a temperature of lt mode2TemperatureFactor gt for the next lt mode2Duration gt iterations It will then alternate between these two temperatures for the respective durations for the rest of the inversion run The default are DualTemperatureMode false model1lTemperatureF actor 1 mode1Duration 99900 mode2TemperatureFactor 1000000 mode2Duration 100 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manua
23. See note below regarding the use of ElevationMaxVoxet relative to ElevationMinVoxet to define the z range of voxels in the geology voxet file Use Auto to specify the top of the 3D GeoModeller project lt Elevation gt is the elevation in metres at which the required set of geophysical responses is to be computed Note that this is not ground clearance but a true vertical elevation using the same Z positive upwards vertical datum and scale as used in the source 3D GeoModeller Project lt IGRF gt lt ReferenceMagneticFieldMagnitude gt lt ReferenceMagneticFieldInclination gt lt ReferenceMagneticFieldDeclination gt in units of nT decimal degrees below the horizontal and decimal degrees east of north lt IncludeBorderEffect gt lt 0 1 gt 0 No 1 Yes include the padding around the model edges in the geophysics Computation lt GeophysicsTypeList gt specifies the type of geophysics responses to be computed with this set of one or more geophysics data types from the following list Gravimetry Gee Gen Ged Gnn Gnd Gdd Magnetism Me Mn Md Mee Men Med Mnn Mnd Mdd where e east n north and d down in a right hand coordinate system Remember north east down NED right hand 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd lt 4 Back gt GeoModeller User Manual 79 Contents Help Top lt 4 Back gt e lt OutputPrefix gt the prefix of the output geophysical resp
24. amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 97 Contents Help Top lt 4 Back gt Geophysical Inversion Run Management In 3D GeoModeller inversion we have a concept of performing one or more inversion runs based on a particular inversion case In this terminology A case is a collection of the data which represents our geo scientific knowledge of the project area that data being a geological model associated geology formation physical property data the one or more geophysical grids to be used jointly in inversion and the specification of the voxel division of the geology model sSe for example NewCase CaseControl An inversion run is a particular instance of inversion processing applied to this case In essence it is a process that investigates the validity of the model testing the model and the associated physical property data against the information contained in a set of one or more independent datasets of geophysical field data NewRun and RunControl commands are used to create and then configure a 3D GeoModeller inversion run In setting up an inversion run we need to specify a series of parameters that will govern how this particular inversion will proceed how many iterations what constraints or limitations we might specify to influence or limit the inversion s ability to adjust values such as geology or physical proper
25. openMPI capabilities are added for the first time so that the software auto senses what CPUs are available and attempts to use them This works well in batch mode Interactive runs however are currently often restricted to just one thread This is due to issues that we need to resolve with the OpenCascade V6 0 technology not being threadsafe The primary intent of offering geophysical inversion in 3D GeoModeller is to let you test your 3D geological model against independently gathered geophysical datasets Provided your geological model is reasonably close to the truth you can benefit from inversion showing you aspects of your model that diverge from these datasets Hidden or inferred 3D structures and geometries are revealed to you and you are then able to make adjustments to your geological model One of the main dangers you will face is using this tool before you have truly created a geological reference model that is close to reality The easiest way to check this condition is via forward modeling Create a grid of the forward model of your model for say a gravitational response and confirm that most of the main features you see in the actual observed data are also to be seen in your forward model Property Optimization Contents Help Top With 3D GeoModeller v2012 we are also releasing technology to concentrate on property optimization prior to any attempts at inversion This is an important and often neglected part of your t
26. s record of that Section s location If you have already generated an inversion result and decide later that you need to present a result on a Section that does not yet exist you can create the required Sections Using 3D GeoModeller open the Project that was copied to the Case Create one or more new Sections and Save the Project Then edit this batch script to generate Section Images on your new Sections ColourScheme The colors for the LithologyColours color scheme are derived from the 3D GeoModeller Project and captured in the Case s inversions xml file When plotting any lithology Field from any voxet the LithologyColours color scheme is always used regardless of what is specified on the command line MaxCols MaxRows VerticalExaggeration and the Section s Aspect Ratio The pixel dimensions of the output JPEG image depend on the aspect ratio of the Section in the 3D GeoModeller Project the aspect ratio defined by MaxCols MaxRows x VerticalExaggeration Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 138 Contents Help Top lt 4 Back gt To produce a set of JPEG image files with a constant ratio of pixels per section meter then Specify MaxCols according to the Section length For example for 1 pixel per 10m of Section length if the Section length is 7 3 km set MaxCols 730 Specify MaxRows to be too large after ta
27. the evolving inversion Voxet is constrained to retain a specified degree of commonality with reference to the nominated Reference Lithology Voxet See SetReferenceLithology Default the Case Voxet There are six main groups of CaseControl commands Contents Help Top SetUseTopo and related commands to specify how the topography should be used and what properties should be assigned to the above topo region IncludeBorderEffect to specify whether or not to include the effect of padded data in the forward modelled responses SetReference commands to specify the Reference Density and to set the magnitude and vector direction for the Earth s magnetic field SetReferenceLithology to specify a Reference Lithology Voxet geology model The commonality constraints maintain a user specified degree of commonality between the evolving inversion geology model and the specified reference model SetLaw set physical properties of geology formations to specify the physical properties of geology formations in terms of a distribution of values defined by a statistical law Allowance for multimodal distributions for the mixed lithologies case Properties density susceptibility and remanent magnetisation For syntax see SetLaw Specify the Properties of Geology Formations For interactive settings see Illustration of dual mode property law settings SetLaw set inversion control properties of geology formations to spe
28. throughout the volume of the 3D GeoModeller 3D Project space such that by default geology boundaries can extend above the topography into the air Considerations with regard to surface topography are Contents Help Top The top of the model set with the lt zMaxVoxet gt parameter should be set such that the topography and the Earth s near surface region are included in the model See Figure 13 b You must explicitly declare that the surface topography should be taken into account by using the CaseControl SetUseTopo command IncludeBorder Effect in effect this command creates another lithology for those voxels where the voxel centroid is at an elevation above the topographic surface In this manual we refer to the Above Topography zone or region An inversion of an observed field on the topography surface is supported as well as observed data from an aeroplane The default values for the magnetic susceptibility and remanence of the Above Topography zone are 0 and cannot be altered The default density value however is the same default density as for every other geology formation the Reference Density value and not the density of air The CaseControl SetAboveTopoDensityLaw SetAboveTopoDensity is used to specify the required 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd lt 4 Back gt GeoModeller User Manual 43 Contents Help Top lt 4 Back gt density property l
29. with the option for variable thickness is available The geometry is defined by a triangulated surface eg TSURF that has uniform thickness and properties for all the triangles variable thickness and properties for each and every triangle IntrepidTask ForwardModelFromDykes DykeSurfaceTrianglesName bifdatadyke5 ts POSC_CoordinateSystem AGD84 AUSTRALIAN_MAP_ GRID_ZONE_53 Comput edGridName demo_dyketest ers product Magnetism drape_elevation_grid myDTM ers Susceptibility node 0 01 0 005 IGRF Date 01 01 2005 method Dyke_Skeletons Rock Properties The aim is to get your 3D geology model to not only be consistent with all the known geology observations but to also be able to explain the main features you can see in regional geophysical datasets such as a Free Air gravity or a Total Magnetic Intensity grid To achieve this you need to specify rock properties and with 3D GeoModeller that is not just a mean value We describe several scenarios where you will change your approach as you gain more familiarity with your 3D interpretation Ifyou are confident of your geology model and have an observed geophysical grid of observations then you can use property optimization to deduce your rock properties needed to explain the observations Ifyou are not so confident that your geology model is perfect perhaps some standard forward modelling of your 3D model for various responses such as grav
30. 100 0 0 BY Log normal 3 0 1 100 Log normal 1e 006 1e 007 100 Log normal 1e 007 0 100 Log normal 1e 007 0 100 Normai 0 0 100 0 0 EF Log normal 3 0 1 100 Log normal 1e 006 12 007 100 FI Log normal 1e 007 0 100 Log normal 1e 007 0 100 Normal 0 0 100 0 0 Log normal 3 0 1 100 Log normal 1e 006 1e 007 100 Log normal 1e 007 0 100 Log normal 1e 007 0 100 Normal 0 0 100 0 0 a 2i 2 01 100 log normal te 006 1 007 100 RRR 609 normai ie 007 0 100 Log normal 1e 007 0 100 Normal 0 0 100 0 0 a Log normal 1e 007 0 100 Log normal 1e 007 0 100 Normai 0 0 100 0 0 Mesozoic Log normal 2 0 1 100 iLog normal 1e 006 1e 007 100 Log normal te 007 0 100 Log normal 1e 007 0 100 Normai 0 0 100 0 0 BE Log normal 1 5 0 1 100 Log normal 1e 006 1e 007 100 _____ e Log normal 1e 007 0 100 Log normal 1e 007 0 100 lormal 0 0 100 0 0 lLog normal 12 006 1e 007 100 E Lo9 normal 1e 007 0 100 Log normal 1e 007 0 100 Normal 0 0 100 0 0 E L09 normal 200 1 100 Log normal 1e 006 1e 007 100 BiB Proterozoic Log normal 1e 007 0 100 Log normal 1e 007 0 100 _ Normal 0 0 100 0 0 BB Proterozoic Log normal 2 0 1 100 Log normal 1e 006 1e 007 100 I EE Loo ormalie 007 0 100 Log normal 1e 007 0 100 Normal 0 0 100 0 0 Granite Log normal 3 0 1 100 Log normal 1 5 005 1e 007 100 a Log normal 1e 007 0 100 Log normal 1e 007 0 100 Normal 0 0 100 0 0 E Basement Log normal
31. 3 0 1 100 Log normal 1e 006 1e 007 100 VK Eq tose sox Ecs With this release there is no requirement to make any assumptions about basal conditions provided that you can constrain the temperature and heat flows at the surface and have some down hole temperature gradient readings to constrain the solution Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 84 Conients Help Top 4 Back gt 32 Forward model Tem Voxel model extent Xmin 50000 Xmax 90000 dx 2000 nX 20 Ymin 100000 Ymax 140000 dY 2000 nY 20 Zmin 10000 Zmax 2000 dz 1200 nZ 10 General parameters Heat Capacity J ka K Boundary Conditions Surface Temperature V Constraint Rayleigh 0 0 100 Surface HeatFlow Constraint Unconstrained TsoTherm Constraint Unconstrained Base Temperature Constraint Unconstrained Base HeatFlow V Constraint Rayleigh 0 03 0 100 Advection Model Advection Sides Iteration Control Iterations 10 000 Max Residual 0 0001 Properties Output Save into ok Cancel L A full and comprehensive set of training notes are available together with Tutorial J to cover aspects of this work The finite difference solver used in 3D GeoModeller v2012 remains the same as used previously The multi grid solver has been developed to speed the solver along but not deployed as yet
32. 4 Back gt GeoModeller User Manual Conients Help Top Properties Page 25 4 Back gt This page in the wizard adapts to the quantity for which you wish to model the response You should review or set your required estimates of density etc distributions for each unit as required Properties Lithology Physical Properties Type Formations X Property Value Ce 2 Density Normal 3 67 1e 005 100 Host General Runtime Settings Page Runtime Settings Interactive Batch Use profile local Number of Cores 1 Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd l Edit Set as defaults 4 Back gt GeoModeller User Manual 26 Conients Help Top Contents Help Top lt 4 Back gt Results Explorer epee tot Dirt preted Rage Towed F Computed Regional Trend This results explorer tool is designed to help you explore the misfit of your forward model data against any available observed grids from the same geophysical phenomenon As there are usually long wavelength trends in the observed data that can not be explained by your model we also give simple trial and error access to trend fitting and removal to help you to see if your forward model is adequate in explaining those frequencies and wavelengths that the model can represent This feedback is done by also storing the spatial response kernels and then in real
33. 40 11 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 161 Conients Help Top q Back gt Appendix 6 Inversion module tasks With the 3D GeoModeller v2012 release of this technology the following functions have example tasks on the standard distribution usually residing near the tutorials ExampleTasks area The bulk of the inversion reference manual is concerned with documenting tasks and sub tasks for geophysicacs responses to your geology model The current state of what is considered a task and what parameters are available can be directly ascertained by examining the invtaskmodel proto file As an aid the following is carried forward from V1 3 to show the evolution and history NewCase Define a new inversion case make a copy of the relevant 3D 3D GeoModeller mapping project CreateCaseFromLithologyVoxet CaseControl Control parameters in the case NewRun Define an inversion run associate this run with a case NewProjectFrom Voxet bring in an external voxet RunControl modify various control parameters used to perform an inversion run SetFixedCells Option to set the lithology within certain cells fixed Run Execute the inversion run NewForwardCase ForwardModelFromCase Calculate the response for the initial state of the run ForwardModelFromVoxet ForwardModelTemperatureForCreateCaseFrom Voxet RunState Extract the litho and proper
34. 7 default true optional int32 Match_Trend_Degree 8 default 2 optional int32 Match_Trend_Rate 9 default 1000 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 47 Conients Help Top 4 Back gt optional ctm CoordinateReferenceSystem coordsys 10 default END required string grid 11 499000 Xmax 503500 dX 7761500 Ymax 7764000 dY 1500 Zmax 1000 dz Vertical sampling parameter See Figure 14 Note also the recommendation to set the elevation of computation of the geophysical solutions to be well above the top of the top voxel of the model You are asked to review the vertical separation and the implied need extra for computer memory The aim should be to balance accuracy requirements speed and being able to manage without going into swap space on your computer Geophysical Grids Horizontal Considerations Geometry Datum Contents Help Top The x y voxel dimensions and voxel centroid positions for the geology Voxet are derived directly from the cell dimensions and positions of geophysical grids Then when using multiple geophysical grids for joint inversion all input geophysical grids must have identical grid cell sizes and cell alignment There is no requirement for the geophysical grids to be aligned exactly with the limits of the 3D GeoModeller Project Rather the li
35. Back gt Cross sections s100000N x Seismic on s100000n 2of2 gt Gravity Magnetic Seismic p Seismic cross section 7 Compute Seismic Xm O 2600 0 5200 0 7800 010400 0 156800 0 20800 0 268000 0 31200 0 386400 0 Physical Properties Partially Defined Ley Time Sampling Number Of Samples 3 000 B 42000 Interval ms i s7007 71333 Space Sampling X Stepping m 100 8500 0 z 2887 9600 00 7846 67 0 00 Z Stepping m 100 ees ow o oor ow os oo ow om Amplitude From Hz v To Hz Ms Geology Cross Section Depth m 0 2600 0 5200 0 7800 0 13000 0 18200 0 23400 0 286800 0 33800 0 3900 0 Distance m W PalaeoMarker Proterozoic Cover M Basement LPalaeozoic W LateGranite1 M Mesozoic Miocene M UPalaeozoic Sos Overview of Geophysical Processes Contents Help Top 3D GeoModeller offers a combination of defining parameters and laws via a formal schema plus a rich variety of command line options with arguments The key file that is used for all aspects of the state of the Inversion engine is inversion xml Equally all procedures or tasks that create set run query are defined in a Google protobuf language The formal definition of these tasks or messages is embodied in nvtaskmodel proto This is distributed in the Tutorials directory See Appendix 3 Sample of Populated Inv
36. GeoModeller spatial as well input_voxet data Model 5d_v2a Casel1 runl initial vo fields node Lithology POSC_CoordinateSystem WGS84 NUTM22 drape_elevation_grid data Avaanna_GDB_G _Alt_SplineRot61_DC_RotBck ers output_gridname ComputedFTGGrid ers PropertyValuesVoxelName data outputdensity vo ExpandedVoxelName data expandedPaddedVoxet vo OutputVoxelName data FTG vo InputVoxetAlreadyProperty false is the voxet a litho model or a density model LanczosTaper true product GravityTensor coordsys END mean_elevation 670 height to calculate forward model at maximum_elevation 1000 continue up the 3D model to accommodate the padding IGRF Date 10 11 2006 method FastFourierTransform BIF1 BIF2 BIF3 BIF4 BIF4b BIF4c BIF5 BIF5b BIF6 BIF6b BIF6c BIF6d BIF7 BIF7b BIF8 BIF8b BIF9 BIF9b BIF10 BIF 10b BIF10c BIF11 BIF12 BIF13 BIF13b BIF14 BIF15 BIF16 Geology Density each lithology has a corresponding density starts from litho 0 1 2 etc node 3 3 0 3 0 3 0 3 0 3 0 3 0 3 0 3 0 3 0 3 0 3 0 3 0 3 0 3 0 3 0 3 0 3 0 3 0 3 0 g 3 2 6 2 6 where input_voxet a Property Voxet the Voxet must contain the relevant properties For example Density for gravity data types Susceptibility as the minimum for magnetic data types and if all three of RemanenceEast RemanenceNorth and RemanenceUp are present they will be used in the magnetic calculations e
37. L1 norm or the L2 norm have been commonly used to create coherent blobs to explain the geophysical signature without any regard to geology We are in the pleasing positon to have the possibility of a well tested and trained geology model in 3D that is consistent with all the known geology thinking of an area as our starting point The obvious stochastic strategy that flows from this is to retain as much as possible the original model while changes are still allowed randomly Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 60 Contents Help Top lt 4 Back gt The aim is to explain the geophysics response while preserving the geology character of the model Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 61 Contents Help Top lt 4 Back gt The physical property distribution laws can be preset in the 3D GeoModeller Project in the physical properties dialog in which case they are correctly recorded in the inversions xml file by the NewCase command Alternatively use this SetLaw command to update the values in the inversions xml file which are then used for all inversions Runs for that Case message LithologyProperty GMT required optional optional optional optional optional optional bool string lithology lt GeologyFormation gt PropertyType proper
38. Make surface shells 8 Accumulate statistics 6 Worme exe 1 Create geophysical WORMS and access a back drop image to track faults Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 11 Contents Help Top lt 4 Back gt Overview of Lithology Properties Contents Help Top The following table shows what types of 2D 3D data processes are available Type Format 3D Grid 2D Section 3D Dykes Gravity yes yes yes Magnetics yes yes yes Heat yes no no Seismic no yes no Gravity Gradients yes no yes Magnetic yes no yes Gradients 3D GeoModeller offers a range of properties and laws that govern the response of rocks Broadly density susceptibility heat flow magnetic remanence and seismic velocity can already be specified 3D GeoModeller supports the common statistical distribution laws of Gaussian Log Exponential as well as allowing multimodal laws up to depth 3 in any one geologic unit Spatially variant laws can also be specified in batch and these are the subject of current developments To help you in the initial stages you can explore properties of units while holding all 3D geometries fixed in 3D GeoModeller A quick interactive forward modeling option to allow you to vary the vertical column of properties to explain the observed signal while holding your 3D geometry constant This is not initially avail
39. This extra work will allow you to create a more complete model that meets the close starting model precondition Scale Resolution Mesh Grids Contents Help Top A requirement to easily switch resolution of your geology model is now met in this release when considering the geophysical response As 3DGeomodeller builds its geology model using an implicit function the actual precision and resolution of the geology model is very flexible but as we look to a geophysical response a hard Nyquist frequency is introduced via the minimum cell size On typical desktop computers a total of around 7 to 10 million cells is an upper limit For regional studies with high resolution geophysical surface datasets this can force a decimation of your study just so the simulation will run This is valid for early calibration and validating the main regional features in your model However there somes a time when you may then wish to verify the high resolution response of your geology model against the geophysics This might take the form of say 200 million cells and the need to run on a cluster or in the cloud using parallel computing respources to achieve a result in a reasonable timeframe With this releae of 3DGeomodeller we include the ability to directly load geophysical survey data that is stored in lines or profiles The tool now automatically creates sections under each profile making it easy for you to then do detail 2D section inter
40. _Trend lt MatchTrend gt Match_Trend_Degree lt MatchTrendDegree gt Match_Trend_ Rate lt MatchTrendRate gt grid lt GeophysicsGrid gt Where e lt Project gt is the relative or absolute path and Project name for the source 3D GeoModeller Project from which the Case will be derived e lt Case gt is the Case identifier or name and will also be the name of a subdirectory of the lt ResultsDir gt within which the Case files will be written e lt zCellSize gt is the Z height in metres of the voxels of the geology Voxet to be derived from the 3D GeoModeller geology model e lt ElevationMinVoxet gt is the vertical elevation of the base of the bottom voxels See note below regarding the use of ElevationMaxVoxet relative to ElevationMinVoxet to define the z range of voxels in the geology voxel file Default is to set this base at the bottom of the 3D GeoModeller project Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 40 Conients Help Top Contents Help Top 4 Back gt lt ElevationMaxVoxet gt is the maximum vertical elevation of the top of the top voxels See note below regarding the use of ElevationMaxVoxet relative to ElevationMinVoxet to define the z range of voxels in the geology voxel file Default is to specify the top of the 3D GeoModeller project lt MeasuredGridsList gt is MeasuredGridsList1
41. a nominated Case subdirectory NewCase command The specification of the division of the geology model into a geology Voxet The x y division of voxels is determined from the geophysical grids the x y voxel positions and dimensions are aligned exactly with the grid cells of the geophysical grids The z division of voxels is specified in the NewCase command For inversion specification of the extent to which the geology formations of the geology Voxet are moveable or are held fixed SetFixedCells command this captures the project geologist s knowledge of the reliability of the geology model which portions are constrained by observed geology that must be honoured and which parts are less reliable and hence allow more scope for change to the model A specific representation of the surface topography derived from the 3D GeoModeller Project NewCase command and specifications regarding use of the topography in generating the lithology Voxet and the assignment of physical property values to the above topography region CaseControl commands Properties of the geology formations From the 3D GeoModeller Project or updated by CaseControl commands These are the physical property data for each geology formation but also include special inversion related properties of formations ie controls the amount of fragmentatio n that is acceptable ShapeRatio defined as the square root of surface area divided by cub
42. by the XML Spy tool just as a place holder The aim of this appendix is to capture every command and option in the batch inversion language in its context A simple text README that also documents the currently supported options is distributed with 3D GeoModeller inversion ManageLithoInversionState xmlns xsi http www w3 org 2001 XMLSchema instance xSi noNamespaceSchemaLocation C dev 3dedit srce InvGravMag InversionState xsd Version 0 Case ZminVoxet 3 141593E0 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual Conients Help Top Contents Help Top Ymax 3 141593E0 ZmaxRequested 3 141593E0 AmbientMagneticMagnitude 3 141593E0 WorkDir String AmbientMagneticDeclination 3 141593E0 Dx 3 1415926535897932384626433832795 Dy 3 1415926535897932384626433832795 Dz 3 1415926535897932384626433832795 ZminRequested 3 141593E0 ReferenceModelPath String Xmin 3 141593E0 IncludeBorderEffect true Name String ZmaxVoxet 3 141593E0 DensityRef 3 141593E0 UseTopo true Ymin 3 141593E0 AboveTopoRemanenceLaw String AboveTopoDensityLaw String InPlace true AmbientMagneticInclination 3 141593E0 Xmax 3 141593E0 VoxetPath String AboveTopoSusceptibilityLaw String Lithology Formation String VolumeRatioLaw String Index 0 CommonalityLaw String Movable true CommonalityVolumeLaw String SusceptibilityLaw String ShapeRatioLaw String RemanenceLaw String DensityLaw String Run CommonalityWeigh
43. complex part of specifying an inversion strategy as there are many optional controls It is common to use a few of these controls together and some are still in place despite them not finding much practical use of late Homogeneous Options There are many options here so we start with an overview of them all then come back and explain each option in detail We also introduce and define some terms to help us explain and control the algorithm This is the third page of the 3D inversion wizard It mostly deals with a mix of Geological Settings Shared settings Proposal i Properties F Allow property change on fixed cell s E Fix lithology frontier V Allow local property different check Constraints Commonality Weibull 0 0010 1 0 100 Probability of property change only 50 Commonality volume Normal 0 0 1 0 100 Shape ratio ogNormal 0 25 0 05 100 Misc Volume ratio ogNormal 0 25 0 05 100 Fix cell lithologies with Always above these Lithologies LateGranite3 LateGranite2 LateGranite 1 MaficDyke Miocene BEoEeag Mesozoic F UPalaeozoic Stratigraphic Order Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 100 Contents Help Top lt 4 Back gt CaseControl and Run Control parameters Run Control gets down to specifics for each variation and constitutes the most
44. ers calculated_Magnetism_Y_3 ers calculated_Magnetism_Z_3 ers 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 95 Contents Help Top lt 4 Back gt layer 3 calculated_Magnetism_X_4 ers calculated_Magnetism_Y_4 ers calculated_Magnetism_Z_4 ers Number of valid grid cells to be used in this work 5625 spike rejects 0 Formation lower bound upper bound My_Diorite 0 080000 0 120000 Middle Sediments 0 000800 0 001200 Lower_Sediments 0 000800 0 001200 Basement 0 000800 0 001200 Levenberg Marquardt returned 96 in 96 iter reason 2 Solution Optimised properties Formation recommended lower bound upper bound Basement 0 0008 0 0008 and 0 0012 Lower_Sediments 0 0008 0 0008 and 0 0012 Middle_Sediments 0 001066859 0 0008 and 0 0012 My_Diorite 0 09983206 0 08 and 0 12 Minimization info info 0 91565 605860 info 1 90713 735296 info 2 4 899823 info 3 0 000000 info 4 0 000000 info 5 96 000000 info 6 2 000000 info 7 2884 000000 info 8 96 000000 Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 96 Contents Help Top lt 4 Back gt info 9 96 000000 objFunL at minimum has sum of squares 9 0714e 004 exit message stopped by small incremental improvement Optimize Job END 22 11 2011 09 56 23 793000 Contents Help Top 2013 BRGM
45. gain j loss j Commonality Volume 100 x Same j Commonality Volume might be assumed to have a normal distribution with a user specified mean and standard deviation for example a mean of zero and standard deviation of 5 Commonality Volume is not as restrictive as FixedCells because we don t need to specify which cells are in common with the reference model but each of the modified models ought to look a lot like the reference model With informative geophysical data we would preferentially accept and keep models with slightly biased characteristics except in the very unlikely situation that the reference model is completely compatible with the geophysical data Thus any difference in the most probable model could be immediately interpreted as being a consequence of the geophysical data For Property ShapeRatio lt Syntax Formation ShapeRatio lt StatisticalLaw gt where lt StatisticalLaw gt lt Normal LogNormal Poisson Equal EqualPlus EqualMinus Weibull Rayleigh gt Associated parameters Mean StandardDeviation Examples LithologyProperty lithology Air property ShapeRatio ProbabilityDistributionFunction type LogNormal mean gy P Y gy prop Y P y YP g 0 0 stddev 0 05 LithologyProperty lithology Water property ShapeRatio ProbabilityDistributionFunction type LogNormal mean 0 0 stddev 0 05 LithologyProperty lithology SedUpper property Shap
46. h r Shape 2 42 h 2r Shape 2 35 h 4r Shape 2 41 h 20r Shape 2 89 Some aspect ratio dependency Cube Shape 2 45 e Prism square base r Xr height r 4 Shape 2 75 Figure 26 The shape ratio for a cylinder and the shape ratio for a sphere The recommended law to use for controlling a Shape Ratio constraint is LogNormal For example ShapeRatioLaw LogNormal 0 0 0 05 First parameter is difference from initial shape Second parameter holds values to a standard deviation of 5 Using 95 2 standard deviation limits and an initial shape value of 2 5 which would be a very smooth object Variations in Shape values 0 25 between 2 25 and 2 75 e This allows considerable variation in ideal body shape AllowShapeRatioTest See also the setting of the ShapeRatio property for each formation in the CaseControl commands SetLaw Type 2 Inversion Control Properties of Geology Formations With each proposed perturbation of the model in each inversion iteration the Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 117 Contents Help Top st sst lt i lt i i i i s S Backi ShapeRatioTest examines the volume of voxels for each formation relative to the outer surface area of those voxels and controls any change that to this ratio according to the distribution defined for each f
47. initialises an instance of a Run Specific files created by the NewRun command are a file called lt CaseID gt _ lt Run gt txt is created in the Case project directory it contains a series of basic inversion case settings a Run block is written into the inversions xml file in the Case project directory The Name of the Run is declared in that block and many further parameters for the Run are set to default values various other files prefixed lt CaseI D gt _ lt Run gt for use for this Run are also initialised in the Case project directory To satisfy specific user requirements for the Run the user will typically execute a series of RunControl commands updating the parameters recorded in the Run block of the inversions xml file A Run command is then executed to perform the actual inversion operation or Run Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 99 Conients Help Top 4 Back gt For example InversionTask NewRun filename InputGeology slab_vertical_20070420c slab_vertical_20070420c xml run Run_1 NumberOflterations 100000 RunControl EDIT There are a set of RunControl commands which are used to further configure or specify the details of an inversion run initialised with the above NewRun command It is reeommended practice to perform a series of inversion runs This is perhaps the most
48. lt FIELDS gt is an optional list of field names to use Example FIELD Density 3MOD uses the field 3MOD in the voxet for the Density mean_elevation is the elevation in metres at which the required set of geophysical responses is to be computed Note that this is not ground clearance but a true vertical elevation using the same Z positive upwards vertical datum and scale as used in the source 3D GeoModeller Project and Geology Model Voxet lt IGRF gt lt ReferenceMagneticFieldMagnitude gt lt ReferenceMagneticFieldInclination gt lt ReferenceMagneticFieldDeclination gt in units of nT decimal degrees below the horizontal and decimal degrees east of north Optional Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 82 Conients Help Top lt 4 Back gt lt IncludeBorderEffect gt lt 0 1 gt 0 N o 1 Yes include the padding around the model edges in the geophysics Computation e lt ReferenceDensity gt is the reference density to subtract from the Density values to convert them to Density contrasts lt GeophysicsTypeList gt specifies the type of geophysics responses to be computed using one or more geophysics data types from the following list Gravimetry Gee Gen Ged Gnn Gnd Gdd Magnetism Me Mn Md Mee Men Med Mnn Mnd Mdd where e east n north and d down in a right hand coordinate system Remember no
49. m s metre so we have 107 s In this case to convert to Eotvos you must multiply by 10 000 Remanence How to get A m from the K nigsberger ratio Qp The magnetisation field strength for a remanent vector in 3D GeoModeller is expressed in units of A m It is not uncommon to find data sources which express the amplitude of remanence in terms of the K nigsberger ratio Qa This is the ratio of the amplitude of remanent magnetisation M to induced magnetisation Mina To resolve this back to amplitude of remanent magnetisation in units of A m you will need to know the susceptibility k of the particular geology formation and the Earth s field strength B First use k and B to determine the induced magnetisation Mina then use Qn to determine the remanent magnetisation Miem With all quantities expressed in terms of SI units the equations are Ming KB u0 Qn Mrem Mina For example if K nigsberger ratio Qp is recorded as 2 Susceptibility k is reported as 1 000 SI x 10 1 000 SI x 10 1 000 x 10 SI units 0 01 SI Earth s field strength B is 50 000 nT 50 000 nT 50 000 x 10 Teslas SI unit and using the constant p 4n x 10 7 Tm A then Induced Magnetisation Mina k SI x B x 107 4n x 107 0 01 x 50 000 x 10 4r x 107 0 398 A m Remanent Magnetisation Myem Qn X Ming 2 x 0 398 0 796 A m 2013 BRGM amp Desmond Fitzgerald amp Ass
50. minimum value or use Auto to have the software automatically calculate this lt maxClip gt maximum value or use Auto to have the software automatically calculate this 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 140 Contents Help Top lt 4 Back gt lt OutputFilename gt the filename of the output avi movie and optionally the relative or absolute path of the output directory which must exist MaxCols MaxRows VerticalExaggeration See additional note in MakeSectionImage For example This function is not available at January 2012 with the protobuf syntax Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 141 Contents Help Top lt 4 Back gt MakeSurfaceShells The MakeSurfaceShells command generates triangular meshed surfaces which delineate the 3D region within which some nominated Field of a Voxet has a specified value or range of values For example the region where the Lithology field has the value 2 or where Density gt 2 1 The output files is an Intrepid meshGrid that is viewable in the 3D GeoModeller 3D Viewer It can also be converted or exported to any number of standard formats This is an important way of communicating to the user exactly what the inversion is doing to your geological boundaries produce surface triangles
51. of the structural element to be used in the homogeneous morphological operation It may be one of the pre defined structural elements listed in 1 or defined in a DefineStructuralElement command Predefined Structural Elements lt Allow gt means allow the homogeneous filter operation e lt Rate gt specifies a repetition rate for the application of this operation in terms of a number of iterations for example HomogeneousFilterRate 10000 will perform this homogenizing filter operation every 10 000 iterations 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 150 Conients Help Top Acknowledgements Contents Help Top q Back gt This second revision of the gravity and magnetic forward modelling and inversion framework was carried out with the support of Commercial Ready program of the Australian Fedral Government The first revision was supported by The National Geoscience Agreement 3D GeoModeller Development Consortium a collaborative project supported by The Geological Survey of NSW GSNSW The NT Geological Survey NTGS The Geological Survey of Queensland GSQ Minerals and Energy South Australia M amp E Mineral Resources Tasmania MRT GeoScience Victoria GSV The Geological Survey of WA GSWA CSIRO and Geoscience Australia GA under the National Geoscience Agreement NGA The development work was carried out by Intrepid Geop
52. predefined structural elements AllowHomogeneousFilter lt 0 1 gt 0O No 1 Yes do HomogeneousFilter topological operator to reduce boundary complexity HomogeneousFilterRate lt rate gt set the number of iterations between repeat applications of the HomogeneousFilter AllowDilationOrErosionFilter lt 0 1 gt O No 1 Yes do DilationOrErosionFilter generates global boundary perturbations DilationOrErosionFilterRate lt rate gt set the number of iterations between repeat 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual Conients Help Top Contents Help Top applications of the DilationOrErosionFilter Commonality tests CommonalityTest lt true false gt CommonalityVolumeTest lt true false gt VolumeRatioTest lt true false gt ShapeRatioTest lt true false gt 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 102 lt 4 Back gt 4 Back gt GeoModeller User Manual 103 Conients Help Top q Back gt Local Method For Modifying Formation Assignments The default boundary modification procedure involves the search for a frontier cell followed by the assignment of a new lithology to this voxel The frontier cell search involves random selection of a voxel This kind of change is called an Inter Formation change while a property only change is called an Intra Formation change Note that an Intra Formation
53. root of distance When one has access to higher derivatives of a potential field say full tensor gravity gradiometry data would behave a lot like induced magnetics in terms of influence on the inversion outcomes On the other hand full magetic tensor data will favour shallower features in your 3D model The big benefit of tensor data or even partial gradient data is that it constitutes a direct measurement of the curvature of the potential field In the case of having tensor data we recommend you work on your geology model so that it includes honouring the shape information that the tensor data contains It is common outside of the Intrepid world to use a point source as a way to model your geology response when tensor data is at hand The state of the art would now include a simple way to deduce shape information in your tensor data This requires work on profiles of observed tensor gradients The new capability in 3D Geomodeller v2012 includes an Import Dyke option that takes as input worms found automatically from a set of located tensor profiles The Intrepid tool to use is Naudyd In this way the shape information is directly being transfered into your geology model prior to any large scale 3D interpretation inversion study 5 independent tensor observations contain a lot more details about the causative signal than just one scalar observation How Geophysical Signals can help your geology model The preferred st
54. so repeatedly smooth the geology boundaries that may have become more complex and irregular A repetition rate can be specified in terms of numbers of iterations between application RunControl message DilationOrErosionFilter_GMT specifies a repetition rate for the application of this operation in terms of a number of iterations required int32 Rate lt Rate gt default 5000 optional bool Allow lt Allow gt default true where e lt Rate gt specifies a repetition rate for the application of this operation in terms of a number of iterations for example DilationOrErosionFilterRate 10000 will perform this homogenizing filter operation every 10 000 iterations lt Allow gt allow the dilation or erosion filter operations lt lt StructuralElementName gt is the name of the structural element to be used in the DilationOrErodeMorphologicalFilter morphological operation It may be one of the predefined structural elements listed in 1 or defined in a DefineStructuralElement command Predefined Structural Elements Homogeneous Morphological Filter Contents Help Top As noted above dilation turns voxels on according to rules based on the number or arrangement of neighboring voxels and erosion turns voxels off according to similar rules The homogeneous morphological filters are specific combinations of the dilation and erode operations Opening is an erosion followed by a
55. specified in the NewCase command these computations do not achieve a reliable modelling of the topography With 3D GeoModeller v2012 we have introduced new technology to adapt the detail modelling to allow you to minimize any stepped effects The stepped topography of the voxel modelled surface can generate artefacts in any geophysical solutions computed close to the topographic surface An alternative crude solution is to exclude the topography from the modelling computations This can be done by setting the lt zMaxVoxet gt parameter at an elevation below the lowest point of the topography This means that the computed solutions will be derived from a simpler flat topped model where the upper parts of the Earth have been sliced off but it also assumes that there are no signatures in the observed data that have been derived from sources above that arbitrarily selected cutoff for the top of modelled data See Figure 13 c For magnetics this will be true where the near surface geology is non 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual Conients Help Top 46 4 Back p magnetic such as across a sedimentary basin For gravity it would require that the gravity data were fully terrain corrected and that the geology above the selected cutoff had a broadly uniform density the same density value as used in the Bouguer full terrain correction Gravity Dataset an
56. that was accepted on those iterations where a change was allowed to occur Inversion does however produce a standard text file that summarizes in plain language the parameters of the current case or run and relevant facts from the progress of the job This is stored in a report file rpt in the directory for the current case or run The aim of this report is to help you quickly get a grasp of what was the outcome for the scenario how that scenario was set up and to gauge if it was successful See Appendix 5 Report File Example for an example of one of these files There are a range of tools that can be used to report the results from this record of the inversion The primary reporting tool is MakeSuperSummaryStats which analyses the data for a user selected range of inversion lithology models derived from one or more inversion Runs and collates these as a set of probabilities the probability of each lithology in each of the voxels of the voxel model This set of probabilities is recorded in a voxet file format A range of additional tools can then be used to present the results from this collated set of lithology probabilities such as generating an image showing the most probable lithology on some specified Section through the 3D model See details below Other useful reporting strategies and tools include The MakeEvolutionMovie command which generates a movie on some specified Section through the 3D model
57. time adjusting your model You are advised to review Tutorial E as this is specifically written to cover much of the basics for the new user wanting to learn how to use the geophysics capabilities 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 27 Contents Help Top lt 4 Back gt Figure 7 Evolution of data misfit rms Vertical gravity gradient Gpp Total magnetic intensity 8 8 Prior 1 Prior 2 Posterior 1 Posterior 2 Posterior 3 Posterior 4 Prior 1 Prior 2 Posterior 1 Posterior 2 Posterior 3 Posterior 4 Ww D o_o RMS misfit Eo RMS misfit nT N o o 2 4 6 8 10 0 2 4 6 8 Iteration 1e6 Iteration 1e6 Example Improvement of misfit during inversion The blue cases are for prior geology only and make no reference to an independent geophysical dataset Hence they reflect the geological uncertainty of the model The other cases show an initial misfit that reduces to a converged solution It is from this point on that 3D GeoModeller begins the job of gathering statistical information about your model Figure 8 GeoModeller _D Fravail 3DWEGMODEL Ne Initiating a limited inversion run via the older graphical interface options Inversion Wizard All the geophysical process wizards have a similar look and feel to each other The stochastic inversion wizard starts the same as the forward m
58. to do large or detailed studies Also the use of Google protobuf technology to handle all the process specification and messaging is added This is a complete rewrite of the batch syntax The protobuf technology includes a proper parser which explicitly informs you of any syntax errors in a manner to help you easily make required corrections The lexicon of the extended geophysics process language is published with 3D GeoModeller It can be found in the tutorial or API directory The actual lexicon is invtaskmodel proto This builds on common components from the main 3D GeoModeller geology area as well as parts of INTREPID So you may need to check other proto files to track down allowable option settings and to see what are the defaults and perhaps even new features since this manual was first published A summary of all the functions processes available is given in appendix A The manual is revised to reflect this new engine room architecture On top of all this several new graphical user interface improvements are made Each variation of Forward modelling can be easily activated through wizard style interfaces Also the full features of stochastic inversion are present in the new GUI for that feature As we have also revised the 3D graphics and introduced generalised support for handling any MeshGrid intergrated with the Geology model very detailed studies are handled easily and the interaction between geology and geo
59. trend of user specified order to the difference We adjust the observed grid by this trend and calculate the misfit We repeat this as requested during subsequent iterations Note that the trends are applied in an iterative rather than cumulative fashion trendN trend iterationO trend detrendIteration1 trend detrendIterationN ERMapper format grids of the trends are written to the CASE directory as lt Case gt _ lt Run gt _ lt Geophysics Type gt _ lt IterationNumber gt _regional You can optionally request progressive trend grids as well 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt Contents Help Top GeoModeller User Manual 52 Conients Help Top CaseControl Contents Help Top lt 4 Back gt The CaseControl commands are used to further configure the details of an inversion Case initialised with the NewCase command The aim here is to set parameters which are common to all simulation situations The magnetic field background density whether to include edge effect reduction stratgies in modelling etc Recommended practice First setup all required specifications for a particular inversion Case and make no further changes to that Case which is then used as the basis for a set of one or more inversion Runs If the details for a Case need to be revised use the NewCase and CaseControl commands to create a new Case a new geological or geophysical model test scenar
60. 005 0 041 11 1 8 1 2 9 5e 006 1 15e 005 0 031 12 1 8 1 6 1 25e 005 1 15e 005 0 031 13 2 2 1 6 9 5e 006 1 15e 005 0 041 14 1 8 1 6 9 5e 006 4 5e 006 0 041 15 2 2 1 6 9 5e 006 4 5e 006 0 031 16 1 8 1 6 9 5e 006 4 5e 006 0 031 17 2 2 1 6 9 5e 006 4 5e 006 0 041 18 1 8 1 6 9 5e 006 1 15e 005 0 041 19 2 2 1 6 1 25e 005 1 15e 005 0 031 20 2 2 1 2 9 5e 006 1 15e 005 0 031 21 1 8 1 2 1 25e 005 1 15e 005 0 041 22 2 2 1 6 1 25e 005 4 5e 006 0 041 23 2 2 1 2 1 25e 005 4 5e 006 0 031 24 1 8 1 6 1 25e 005 4 5e 006 0 031 25 1 8 1 2 1 25e 005 4 5e 006 0 041 26 2 2 1 6 1 25e 005 1 15e 005 0 041 27 2 2 1 6 9 5e 006 1 15e 005 0 031 28 2 2 1 2 1 25e 005 1 15e 005 0 031 29 2 2 1 2 9 5e 006 1 15e 005 0 041 30 2 2 1 2 9 5e 006 4 5e 006 0 041 31 2 2 1 2 9 5e 006 4 5e 006 0 031 32 2 2 1 2 9 5e 006 4 5e 006 0 031 Finished simulation work These set of tasks can be run in parallel as each task is completely independent of the others Each task places its output using a Project Case Run_NN Thermal vo template A super computer or the cloud can be very useful in doing large scale studies Compile Parameter Sweep Statistics For both heat and potential field parameter sweep situations once the runs are all finished and the results of each simulation are collected a follow up task is to compile the results statistically There are up to 10 fields that have been calculated each with many results These are compiled into one statistical voxet using th
61. 0070420c slab_vertical_20070420c xml run Run_1 number_of_iterations 70000 Utility DumpVoxet This is a deprecated command being replaced by a new voxet utility tool in Intrepid The DumpVoxet utility simply dumps the content of the nominated Voxet to a stream of ASCII text in the command window This can be captured to a text file by redirecting the output stream to a file Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 145 Contents Help Top lt 4 Back gt Morphological Filter Commands When this inversion algorithm was first proposed a great deal of effort has been expended using morphological filter operations A description of these options now follows They are not the preferred options any longer and the previously mentioned controls or constraints of Commonality and Shape ratio are recommended During an inversion Run any change to the lithology of a voxel implies a change to geology boundaries A consequence of such random changes is that geology boundaries can progressively become very irregular and non geological in character The morphological filters use the morphology based operations erosion dilation and combinations of these to add or remove voxels from these complex geology boundaries to achieve a degree of smoothing of the boundary These operations tend to join separated portions of features or separate touching features and
62. 3D GeoModeller v2012 The aim here is to calculate dyke swarm responses for any required gravity or magnetic component including the full tensor gradients The geometry of the dykes can be specified in 2 ways depending upon your progress in defining the detail of your model The only way to execute this functionality is via the mtdyke tool PROTOBUF EXAMPLE A An example of tensor dyke response forward modelling from a databse of Hot Spot point observations The job of linking simple thin sheets is to be handled by the user prior to this task using such tools as Naudyd from Intrepid A Hot Spot has attributes of X Y Z Depth to top Length Width Height Strike Plunge and a litho code IntrepidTask ForwardModelFromDykes InputDykesName bifdatadyke_imported DIR InputField Susceptibility POSC_CoordinateSystem AGD84 AUSTRALIAN MAP GRID_ZONE_53 ComputedGridName teisa_dyketest ers product MagneticTensors DrapeSurfaceGridName OutputPrecision IEEE4ByteReal OutputGridCoordSysType END ObservationHeight 0 0 Grid_Size 10 0 Average_Dyke_Length 140 Susceptibility node 0 01 0 01 IGRF Date 01 01 2005 method Dyke_Skeletons 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 91 Contents Help Top lt 4 Back gt PROTOBUF EXAMPLE B Here is an example of a dyke response from a 3D thin sheet The skeleton of the dyke
63. Chil s J P Aug C Guillen A and Lees T 2004 Modelling the Geometry of Geological Units and its Uncertainty in 3D from Structural Data The Potential Field Method AusIMM Orebody Modelling and Strategic Mine Planning Perth WA Guillen A Courrioux G Calcagno P Lane R Lees T and McInerney P 2004 Constrained gravity 3D litho inversion applied to Broken Hill Extended Abstract ASEG 17th Geophysical Conference and Exhibition August 2004 Sydney Guillen A Lane R and McInerney P 2007 3D probabilistic inversion of potential fields data using geological constraints Paper presented at EGM 2007 International Workshop Innovation in EM Gravity and Magnetic Methods a new Perspective for Exploration Capri Italy 16 18 April 2007 Lane R and Guillen A 2005 Geologically inspired constraints for a potential field litho inversion scheme Proceedings of IAMG 05 GIS and Spatial Analysis Volume 1 181 186 ISBN 0 9734220 1 7 Mar chal A 1984 Kriging seismic data in presence of faults in Geostatistics for Natural Resources Characterization Eds G Verly M David A G Journel and A Mar chal Part 1 pp 271 294 Reidel Dordrecht McInerney P and Lees T 2004 Broken Hill Geological Modelling Project Using 3D WEG Geological Editor Final Report Report prepared by Intrepid Geophysics for pmd CRC Project C6 Metropolis N and Ulam S M 1949 The Monte Carlo Method J Am Stat Ass
64. D GeoModeller computed solution at constant elevation typical airborne survey observations are recorded at variable elevation The implications of this are Magnetics In practical terms many regional airborne surveys are flown at a sufficiently uniform elevation that the data can be regarded as having been acquired at the mean survey elevation If the dataset must be upward continued see below then the error in this approximation is further reduced In some circumstances this approximation would introduce unacceptable errors these might include significant height variation in rugged terrain and low level surveys where the varying elevation of survey observations was close to near surface magnetic sources Gravity Observation height and the shape of the terrain are important factors in all gravity surveys so the Free Air Bouguer and full terrain corrections are applied to gravity datasets The Bouguer or terrain corrections treat the Earth as having a uniform density the Bouguer density and are designed to remove the gross error due to the contrast between earth and air and the complex shape of the boundary between them The Earth of course does not have uniform density and the observed geophysical response to a near surface anomalous mass within the Earth may vary significantly with survey elevation Since 3D GeoModeller geophysical computations are voxel based with voxels having a discrete z height lt zCellSize gt
65. EF denvolume_m_1 vo AllowAdaptiveFilter False AllowHomogeneousFilter False HomogeneousFilterRate 100000 AllowDilationOrErosionFilter False DilationOrErosionFilterRate 5000 IncludeBorderEffect True IncludeAboveTopoFacesInShapeRatio True IncludeOutsideFacesInShapeRatio True ProbabilityOfPropertyChangeOnly 0 000000 PriorOnly False UseAboveTopoFormation False SetOutputMisfits True AllowPropertyChangeOnFixedCell True AllowNeighbourPropertyDifferentCheck True Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 160 Contents Help Top lt 4 Back gt Contents Help Top LargeMisfitRMSThresholdFactor 1 000000 LargeMisfitTemperature 1 000000 PreserveTopology False CommonalityVolumeWeightType 1 CommonalityWeightType 0 VolumeRatioWeightType 1 ShapeRatioWeight Type 1 AllowCommonalityVolumeTest False AllowCommonalityTest False AllowVolumeRatioTest False AllowShapeRatioTest False Total Iterations 100000 Total Proposals 99999 TotalAcceptanceCount 609 InterFormationChangeAcceptances 320 of 99999 SameAcceptances 289 of 0 InterFormationChangeAcceptances 320 of 99999 IntraFormationChangeAcceptances 0 of 0 TotalRejectCount 99679 PreserveTopologyRejects 0 of 0 CommonalityRejects 0 of 0 CommonalityVolumeRejects 0 of 0 VolumeRejects 0 of 0 ShapeRejects 0 of 0 GeophysicalRejects 1 99679 of 99999 End Inversion run 19 6 2007 46
66. Each of the movie frames is a snapshot of the lithology on that Section for a single 3D lithology model By collating a subset of these snapshots the movie shows the evolving lithology on that Section during the course of the inversion reproducing the lithology model at any specified iteration number of the inversion reproducing the geophysical signature grids for any such discrete lithology model plotting graphs of the inversion misfit values MakeEvolutionMovie The MakeEvolutionMovie command produces a movie that shows the evolving lithology during the course of the inversion Run on some specified Section through the 3D model Each of the movie frames is a snapshot of the lithology on that Section for a single 3D lithology model A collation of these snapshot images movie frames into a movie presents not only the evolution of the models during inversion but actually presents the geology of literally hundred of discrete geology models Note that the movie does not show every iteration but rather samples the changing lithology on that Section at a user specified interval say every 20 000 iterations so Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 130 Contents Help Top lt 4 Back gt each movie frame captures the net lithology changes over that specified interval of iterations The frames are initially standard JPEG
67. GeoModeller User Manual 114 Contents Help Top lt 4 Back gt where e Lis the likelihood function Pis the probability function when generating models The construct B A indicates outcome B conditional on outcome A C is the current model and P is the proposed model In contrast a Metropolis test only involves the likelihood ratio The Hastings addition to this procedure compensates for any asymmetry in the probability of generating different proposals if the probability of generating the proposed model given the current model is different to the reverse probability of generating the current model given the proposed model Syntax message CommonalityTest_GMT enum Commonality WeightType none 0 LocalAbundance 1 LocalCommonality 2 GlobalCommonality 3 required Commonality WeightType SetWeights default none optional bool Allow 2 default true where lt none gt default no additional weighting applied LocalAbundance means that the weights will be derived from the 6 face neighbors of the voxel for which a change of formation is proposed GlobalCommonality means that the weights will be derived from an assessment of the effect of the proposed change on the Same values where the assessment involves the entire voxel model not just the 6 face neighbors of the voxel for which a change of formation is proposed LocalCommonality means that the weights will be derived fr
68. GeoModeller User Manual Forward modelling and inversion with 3D GeoModeller 1 Contents Help Top lt 4 Back gt Forward modelling and inversion with 3D GeoModeller Ser ener X v a E 3 c a a a fe 6 s G g E a sa Structural Geology 3D Modelling amp Geophysical Modelling in 2D 3D Gravity Magnetics Heat Flow and Seismic data Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 2 Contents Help Top lt 4 Back gt Geology Model C Improved Inversion model Most Probable Authors Phil McInerney Richard Lane Ray Seikel Antonio Guillen Helen Gibson and Des FitzGerald With V2 0 most of the geophysical work was undertaken by Horst Holstein Dominik Argast and Des FitzGerald The text is updated by Des FitzGerald Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid lt 4 Back gt GeoModeller User Manual 3 Contents Help Top lt 4 Back gt Introduction This technology does not replace the expertise of the geoscientist Instead it enables the geologist to use his experience and knowledge to devise a viable geological model that is consistent with geophysical observations A geologist can produce many viable 3D geological interpretations in just a few days of work 3D GeoModeller does this by using implicit functions to model each seri
69. IncludeBorderEffect gt lt GeophysicsTypeList gt lt OutputPrefix gt where lt CaseXML gt the relative or absolute path of the XML project file for the 3D GeoModeller inversion Case lt eCellSize gt is the East size metres of the voxels of the geology Voxet to be derived from the 3D GeoModeller geology model lt nCellSize gt is the North size metres of the voxels of the geology Voxet to be derived from the 3D GeoModeller geology model lt zCellSize gt is the Z height in metres of the voxels of the geology Voxet to be derived from the 3D GeoModeller geology model lt EastMinVoxet gt is the easting minimum of the voxet Use Auto to set this west edge of the 3D GeoModeller project lt EastMaxVoxet gt is the easting maximum of the voxet Use Auto to set this east edge of the 3D GeoModeller project lt NorthMinVoxet gt is the northing minimum of the voxet Use Auto to set this south edge of the 3D GeoModeller project lt NorthMaxVoxet gt is the northing maximum of the voxet Use Auto to set this north edge of the 3D GeoModeller project lt ElevationMinVoxet gt is the vertical elevation of the base of the bottom voxels The vertical elevation of the centroid of the bottom voxels will be zCellSize 2 above this value Use Auto to set this to base at the bottom of the 3D GeoModeller project lt ElevationMaxVoxet gt is the maximum vertical elevation of the top of the top voxels
70. MeasuredGridsListN lt ResultsDir gt is automated to put order into the situation Basically a Case Run subdirectory scheme is used And where lt MeasuredGridsList gt specifies each of the geophysical grids to be included in the inversion Each list nominates the type of geophysical dataset specifications for the dataset and user choices about how the inversion process will match the computed and observed grids for that dataset lt MeasuredGridsList gt parameters are lt Geophysics Type gt lt MeanElevation gt lt Precision gt lt MatchTrend gt lt MatchTrendDegree gt lt MatchTrendRate gt lt GeophysicsGrid gt Where lt Geophysics Type gt specifies geophysics data type from the following list as repro duced from the commontaskmodel proto file see the API directory for up to date list Gravimery Gxx Gyy Gzz Gxy Gxz Gyz Gee Gnn Gdd Gen Ged Gnd Gz Magntism Mxx Myy Mzz Mxy Mxz Myz Mx My Mz Mee Mnn Mdd Men Med Mnd Me Mn Md TMI Temperature GravityTensors MagneticTensors where e east n north and d down in a right hand coordinate system Remember north east down NED right hand lt MeanElevation gt is the survey observation level for this dataset in metres Note that this is not ground clearance but a true vertical elevation using the same Z positive upwards vertical datum and scale as used in the source 3D GeoModeller Project Also an elevation grid can be specified if it is availa
71. Model 0 FromVoxet 1 FromLawMean 2 FromLawRandom 3 lt and where FromModel means use the Case voxet This voxet is one of the Case files created by the NewCase command and contains Lithology values sourced from the 3D GeoModeller geology model specified in the NewCase command e FromVoxet lt InitialLithologyVoxetDesc gt e Where InitialLitholgyVoxetDesc lt intitalLithologyVoxetPath gt lt LithologyVoxetField gt and the InitialLithologyVoxetPath specifies the relative or absolute path to a voxet file which must contain a field named lt LithologyVoxetField gt Lithology by default Attention to Detail If you reference an independent voxet that voxet must meet specific conditions The voxet parameters such as dimensions and size must match exactly the dimensions specified in the Case inversions xml it must contain a Lithology property the values of the Lithology property must be integers ranging from 0 to n which correspond to the n geology formations defined for the Case inversions xml DensitylnitialiseStyle The typical initial density for a 3D GeoModeller inversion Run is generated by applying the density law for each lithology to the lithology voxet defined above Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 112 Contents Help Top lt 4 Back gt There are two variants for how the law can
72. NewCase command records these settings in the inversions xml file of the Case To change these values use the CaseControl commands SetReferenceMagneticFieldMagnitude SetReferenceMagneticFieldInclination SetReferenceMagneticFieldDeclination Ifa reduction to the pole RTP correction has been applied to the magnetic dataset then the effective direction for the Earth s magnetic field appropriate to an RTP dataset is vertical Inclination should be set to 90 and the declination can be set to 0 The field strength magnitude should be that value determined by the IGRF calculator for the given latitude longitude location of the Project Consideration should be given to whether it is appropriate to use RTP data Advantage RTP data can simplify the shape of anomalies and the anomalous response is positioned above the magnetic source if the response is due solely to induced magnetisation Disadvantages are RTP is yet another process applied to data and can be unreliable at low magnetic latitudes More importantly however RTP will produce spurious results where there are magnetic sources with remanent magnetisation 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 50 Conients Help Top lt 4 Back gt Recommendation Do not use RTP data where there is reasonable evidence for sources with remanent magnetisation Instead use the field data as recorded
73. RGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 34 Contents Help Top lt 4 Back gt and then develop techniques to utilize the full signal during interpretation has been developed It is expected to deploy some of the outcomes in 3D GeoModeller inversion in 2012 Support for Seismics At the lowest level each rock unit can have a seismic velocity 3D Geomodeller v2012 also has a new capability to import and analyse micro seismic point clouds with a view to interpretation of unknown fault planes and jointing that a fracturing program might be inducing Currently the recommended way to create a 3D velocity model is to use the domain kriging feature If you have 2D seismic shot point data you can choose to work in time or depth Either way the mechanism to get an optimum velocity model constrained by a proper geostatistical analysis of your data involves the following steps e Import the seismic section data including the shot points and velocities Use the 3D observed points option Itis recommened that you create a 3D geology model of the sedimentary geology using the standard 3D geology modelling techniques Create one or more variograms of your velocities constrained by each geology unit This is known as domain kriging Your seperation distances between samples is calculated following the trends of the geology model implicit model potentials Interpolat
74. True False status of the PreserveVerticalRelationship property for each pair of formations in the computed model This is done by defining a set of flags for each formation These flags are all false zero by default A flag is set to true one if the target formation is not allowed to occur above the source formation If there are N formations in the computed model and the source formations are thought of as the rows of a matrix and the target formations as columns the complete set of PreserveVerticalRelationship properties form an N by N matrix If the upper left corner of the matrix is the youngest formation and the formations are ordered from youngest to oldest across the columns and down the rows then entries in the upper triangular part of the matrix i e the top right half above the leading diagonal are used to preserve normal upward younging vertical relationships Entries in the lower triangular part of the matrix below the leading diagonal are used to specify overturned relationships Note that this shorthand arrangement for assigning the PreserveVerticalRelationship properties implies knowledge within the routines of the relative age relationships between units Internally the program Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 120 Contents Help Top lt 4 Back gt assigns an AgeRank property to each of the computed formations from inf
75. able in the GUI and must be accessed as a batch job Bounded least squares fit of a unique property value for each unit found by forming a matrix of contributions from your model against the geophysical observations 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 12 Conients Help Top q Back gt Stages where Inversion is used Contents Help Top There are several times in the process of building a 3D geological model where you might turn to the geophysical data and ask for some guidance from it Stage 1 Beginning Primary geological units and depths where little is known about the geology the first place to turn is to regional geophysical datasets Quite a lot of information about types of structures and geological setting of basement rocks can be quickly inferred Some tools such as Euler Deconvolution Geophysical Worms Matched Filtering and 2D sectional modeling and inversion Naudy are commonly used to build up the starting concepts Stage 2 No Geology Constraints 3D analytic inversion such as the code from the University of British Columbia www eos ubc ca research ubcgif is used to create 3D bodies of a compact but fuzzy nature to explain the gravity or magnetic signal There is little geological input used or required When using default settings for UBC GIF inversions you derive broad guidance for subsurface geological mapping Stage 3 Ma
76. age 4 of the wizard r Definition Description Definition of the mode component Simulation Parameters Mean 0 001 Standard deviation p Statistical law Rayleigh Weibull Log normal AllowCommonalityTest In batch Commonality is a geology test that can be applied during the inversion as part of RunControl One needs to determine the additional weightings that will be used to control the likelihood of accepting or rejecting a proposal based on the change in Commonality These weights attempt to correct for any bias introduced to the test by the procedure used to form the proposal In many of the geological tests the probability of generating a particular outcome B given the present circumstances A is not the same as the reverse transformation P B A is not equal to P A B Consequently a simple Metropolis test will not be adequate to produce samples from the specified distribution The solution is to calculate the probability of these forward and reverse transformations and use a Metropolis Hastings acceptance test To generate geological models with a specified distribution using a Metropolis Hastings acceptance test the acceptance probability given by the following expression mihn L Proposed P Current Proposed _ 1 L Current P Proposed Current Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid lt 4 Back gt
77. although possibly upward continued and specify appropriate magnetic remanence physical property values for selected modelled geology formations Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 51 Conients Help Top Trend Matching 4 Back gt With 3D GeoModeller v2012 we now support Dykes and their geophysical contribution to the observed signal There is an unresolved complication when trying to represent and model narrow magnetic sources using relatively coarse voxels Rather than manage the dykes within this voxet framework it is envisaged to allow for extra surfaces of minimum volume but significant geophysical signal to reside outside the voxet The contribution to say the magnetic signal can then be summed from both the voxet and the 3D dykes This latter capability exists only in batch as the 3D GeoModeller v2012 work program did not allow for this to be finished in time The total number of voxels that can be used in 3D GeoModeller inversion and achieve a useful result within a practical timeframe say 12 24 hours of computation is currently about 7 million voxels This effectively determines a limit on the size of voxels that can be used it frequently is the case that the voxel dimension is larger than you might prefer In other words there can be a loss of geological resolution when the 3D geology model from 3D GeoModeller is converted
78. and postulate a change to the model 12 Assess the geological acceptability of the changed model 13 If geologically accepted compute the geophysics responses of the changed model 14 Using the geophysics misfits compute the likelihoods of the changed model During the initial part of the inversion the data misfit for each field of the current model follows a generally decreasing trend As the data misfit reaches values more in keeping with the specified data uncertainty values the rate of change in misfit decreases and finally stabilizes after initial burn in and we begin to store the models These stored models are an exploration of the probability space of acceptable models At Step 12 the changed geological model may be rejected on the basis of any one of the geological tests in which case the proposed change is discarded and the inversion commences a new iteration at Step 11 At Steps 13 and 14 each of the requested geophysics fields are computed in turn and their likelihood evaluated If the changed model is rejected on the basis of a computed likelihood the proposed change is discarded and the inversion commences a new iteration at Step 11 Steps 13 and 14 are repeated sequentially for each of the requested geophysics fields and any requested tensor components If the changed model is accepted on the basis of the computed likelihood for all requested geophysics fields and tensor components the proposed change is retained and t
79. arting position when considering magnetics is to assume you can explain all of the observed magnetic anomalies in your observed datasets with the current Earth s magnetic field Often there is no need to consider any other explanation for the observed magnetic field With all of the above in mind it is expected you will find the following Gravity Only inversion Is poor for depth estimates Is good for the volume or mass of geological anomaly e Induced Magnetics inversion Depth to top of body is good Orientation of body is also good Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 18 Contents Help Top lt 4 Back gt Poor estimate of body volume e Joint Magnetic amp Gravity Get both depth and volume Remanence If you have existing or prior knowledge that magnetic remanence is a factor you will want to be able to take this into account in your model As above you start out assuming that all magnetic responses can be explained just assuming an induced magnetic field For the next step the primary assumption you are required to make is the direction of the remanence vector This should be backed up by some field observations if at all possible Often what you are reduced to doing is making a guess of the most likely average direction This takes the form of three direction cosines one parallel to your dip vector and the other two at
80. as the Initial Voxet but it need not be Note that voxet is also a generic term referring to any file of voxels 3D in the GoCAD voxet format In these notes Voxet with uppercase V refers specifically to a 3D geology model Kernel is the geophysical unit response function used to record the geophysical response at the designated measurement elevation for every possible voxel in the 3D geology model Voxet and its surrounding buffer zone for each of the required geophysical data types for example magnetism gravimetry vertical gradient of gravity Gdd and for unit physical property contrast for example for unit density The Kernel is computed once and stored for reuse in later 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 31 Contents Help Top lt 4 Back gt Runs Figure 9 Symbolic representation of an inversion Case and one or more associated inversion Runs Figure 10 Mapping Project Observed gravity and or litha fegions properties magnetic data NewCase CaseControl Voxet ForwardModelFromProject NewRun RunControl SetFixedCells Run Runt pf una FopwardModelFromCases MakeEvolutionMovie 22 MakeSummaryStats MakeSuperSummaryStats Calculated gravity Gravity and or Movie of section and or magnetic data Voxet Geology magnetic data misfit showing model graph s evolution ForwardModelFromVoxet
81. ase_1 run Stats inputvoxet SuperSummaryStats_Case_2_Run_1_iterations_4000000_10000000_80_super inputfield MeanDensity operand GE eg gt lt gt lt or LE GE INSIDERANGE valuel 0 1 Do_Tops true output tmpdesl_GE_Opt1 ReportFile SurfaceShell rpt Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 142 Conients Help Top lt 4 Back gt MakeHistogram The MakeHistogram command is used for reporting the distribution of values of a specified Field of a discrete geology voxet grouped by Lithology The command is intended for reporting the distribution of physical property values Density Susceptibility and Remanence for an individual geology model a discrete geology voxet The nominated voxet file must contain a field called Lithology The specified Field data values are first grouped by Lithology then the histogram binning is applied The output is recorded in a simple ASCII text file with separate bin counts for each Lithology of the Project Create a Histogram report for an inversion run using the specified file message MakeHistogram_GMT required string filename lt CaseXML gt optional string case 2 use this for inversion stats optional string run 3 required required required required required required string voxet lt Voxet gt string litholo
82. ask The basic technology involves a least squares deterministic search through your proposed properties for each lithology given an observed geophysics grid and a starting geology model The recommended proceedure is to then look for a set of properties that best fit over all your project the geology and the observed data This usually means that you can see if any reasonable property distributions can be found with the geometry you propose to explain the geophysical response If nothing can be found that meets the physical admissibility test you model is not good enough to even attempt inversion You should be able to deduce the major weaknesses and make some re adjustments This step is critical as often your rock property knowledge especially of bulk properties at depth is poor If you cannot meet this precondition you are going to basically waste your time running 3D GeoModeller inversion You are advised to continue working on your 3D Geology model 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 5 Contents Help Top lt 4 Back gt Using sections and profiles to examine the profiles of the forward model response vs observed Using Euler depth methods to confirm your depth to magnetic basement assumptions e Using multi scale edge detection or analytical signal enhancement to get the main faults volcanics and basin units blocked out and constrained better
83. ation Description Unit g cm3 Law simulation Normal 2 67 0 2 80 Normal 3 5 0 2 20 Help Example of setting dual mode property laws interactively within 3D GeoModeller SetLaw Type Syntax Details Units 1 Physical Properties The CaseControl SetLaw sub task is used to specify both physical properties for geology formations this section and also special inversion control properties of formations SetLaw Type 2 Inversion Control Properties of Geology Formations In Inversion there are three physical properties that can be set that will influence outcomes Density Susceptibility and Remanence Other physical properties are required for Heat Seismic etc For Property Density The density value for a formation is specified in absolute terms and not in terms of density contrast But note that density contrast relative to the Reference Density is used in the computation of the gravity response see Reference Density SetAboveTopoDensity Units for Density Use g cm The lt StatisticalLaw gt is typically Normal with Mean and Standard Deviation parameters Example Pitfield_Volcanics Density Normal 2 81 0 01 100 meaning that the Pitfield_Volcanics formation consists of a single lithology 100 with a Normal distribution around a mean of 2 81 g cm and standard deviation of 0 01 g cm 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 66
84. ause of the small sample size and because of natural small scale variations caused by such events as alteration of the rock weathering of near surface samples By contrast the inversion process is applied to voxel volumes of rock which may be cubic kilometres in size The expected variation of physical properties for such huge voxel samples would be much less than would be observed for a set of small hand specimens Furthermore inversion experience tells us that where the standard deviation is too broad the inversion process rapidly achieves a good match to any field dataset and it is likely that the inversion has not effectively tested the validity of the proposed 3D geology model 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual Conients Help Top Contents Help Top 65 4 Back gt Illustration of dual mode property law settings Figure 19 Gui TCollection_ExtendedString e1ed5b law Definition Definition of the mode component Definition of the mode component Parameter s module Parameter s module mean Value 2 67 mean Value 3 5 Standard deviation 0 2 Standard deviation 0 2 Modes Mono modal Statistical law Statistical law Bi modal Normal O LogNormal Equal Normal O LogNormal Equal O Tr modal Poisson Equal Plus Equal Minus Poisson Equal Plus Equal Minus Percentage of Population Percentage of Popul
85. aw for the Above Topography zone There are practical reasons why this zone might be modelled with a density value which is not the value for air see the discussion in SetAboveTopoDensity Acellis defined to be above the topography when its centre is above the topographic surface Figure 13 Top of model for which the geophysical response will be computed Top of model for which the geophysical response will be computed The effects of surface topography are always a component of the observed geophysical responses for both ground and airborne surveys a The specification of lt zMaxVoxet gt in the NewCase command determines the upper limit of the Voxet for which the mod elled geophysical response will be computed The recommended choice is to set lt zMax Voxet gt to be at an elevation above the highest point of the topography b Setting lt zMaxVoxet gt at a lower elevation may simplify the model but also removes the ability to model sources that may exist above the arbitrarily selected lower cutoff c Geophysical Dataset Types Units and Grid File Formats Grids 3D GeoModeller Inversion uses geophysical data in grid format Several dataset and grid geometry requirements are noted here See also further geophysical considerations in the following sections in regard to gravity topography and the Earth s magnetic field 3D GeoModeller Inversion can be performed on any one or more of the potential field datasets liste
86. be applied The full statistical law approach can be used to yield a statistically controlled random distribution of density values for each formation Alternatively a uniform density for each voxel of a given formation can be used simply by assigning the first parameter of the formation density law to each voxel With FromVoxet it is also possible to nominate a specific voxel model containing density values Use this method to continue an inversion from a previous Run or if you want to use a voxel model generated by independent means Deafult is LawMean SusceptibilitylnitialiseStyle Syntax and concepts same as DensityInitialiseStyle DensityInitialiseStyle Attention to Detail Units Susceptibility value must be in SI units Attention to Detail For FromVoxet the referenced voxet must contain a Susceptibility property with values of magnetic susceptibility in SI units RemanentMagnetisationlnitialiseStyle Syntax and concepts same as DensityInitialiseStyle DensityInitialiseStyle Attention to Detail Units Remanent magnetization values must be in units of A m Attention to Detail For FromVoxet the referenced voxet must contain a Remanence property with values of remanent magnetization values in units of A m Geology Tests Commonality Four methods or probability functions have been devised to suit this purpose These are Commonality CommonalityVolume ShapeRatio and VolumeRatio An proposed change tests use th
87. ble This option is a fall back when you do not have a drape elevation grid lt Precision gt is the estimation of the standard deviation of the measurement errors for this dataset assuming a Gaussian distribution of errors lt MatchTrend gt lt false true gt where false do not match trend true yes match trend This refers to the removal of regional gradients or trends from the observed geophysical dataset detrending lt MatchTrendDegree gt lt 0 1 2 3 gt specifies the degree of detrending 0 isa DC shift only 1 is a planar gradient trend across the dataset Recommend use 0 or 1 Options 2 and 3 introduce more curvature into the detrending lt MatchTrendRate gt is the repetition rate in terms of numbers of iterations for applying the detrending To apply detrending once only at the start specify 0 lt GeophysicsGrid gt is the relative or absolute path filename of the geophysics grid data file The range of grid format files supported can increase as more drivers are added to Intrepid and made available to this context ERMapper Oasis Montaj and an ASCII format known as semi are core formats 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 41 Contents Help Top lt 4 Back gt Contents Help Top The Z elevation of voxel centroids will range from ElevationMaxVoxet nZ x zCellSize zCellSize 2 to ElevationMaxVo
88. bodies or to disappear Recommended to not use this It is off by default When set PreserveTopology prevents the complete elimination of a unit by automatically rejecting a proposal that would eliminate the last voxel assigned to a particular formation PreserveTopology uses a local environment local 8x3x3 vertex neighborhood for checking whether new regions have been created or old regions have been eliminated This is clearly a compromise between a complete calculation that would require analysis of the entire mesh and processing speed This option hence operates to reduce but not entirely eliminate the possibility that a region will split into 2 or more regions This control is not recommended as it tends to promote extremely convoluted boundaries Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 107 Contents Help Top lt 4 Back gt 100000 Reject Criteria V Reject proposals based on Geological Criteria Allow commonality test Allow commonality volume test 7 Allow volume ratio test Allow shape ratio test Advanced Tuning Options speed of initial solver SetOutputMisfits SetOutputMisfits is simply an output option By default it is off If you SetOutputMisfits 1 on then the global misfit values the least squares differences between the field and the computed geophysics grids will be written out to a misfits file approximatel
89. c intensity TMI data Me Mn Md nT Vector components of magnetic intensity measured in the east north and Z downwards directions Mee Men Med Mnn nT m The components of the magnetic gradient Mnd Mdd tensor where e east n north and d down in a right hand coordinate system 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 45 Conients Help Top Contents Help Top 4 Back gt Geophysical Grids Vertical Considerations Acquisition Elevation 3D GeoModeller computes geophysical responses for all geophysical data types at either a single fixed vertical elevation the lt MeanElevation gt parameter a constant heigth above the ditigital terrain or onto a provided drape surface By elevation we mean a true vertical elevation specified in terms of the Z positive upwards framework of the 3D GeoModeller geology model it is not a survey height or mean terrain clearance Of course geophysical signals such as gravity have a convention of the field being given with Z positive down From here we start the need to distinguish between geometry a right handed coordinate system in East North Up for XYZ and conventions the geophysics field might be measured in possibly the same convention but often not Thus For joint inversion of multiple data types all geophysical grids can have varying effective acquisition heights In contrast to 3
90. calTests 17 default true used to be PriorOnly optional bool AllowGeologicalTests 18 default true optional bool PreserveTopology lt PRESERVE gt default false optional bool SetOutputTrendGrids lt TrendGrids gt default false optional bool SetDualTemperatureMode lt DUALMODE gt default false optional double SetLargeMisfitTemperature lt MISTEMP gt if dual temperature mode is false optional double SetLargeMisfitRMSThresholdFactor lt MISRMS gt optional double ModelTemperatureFactor 24 if dual temperature mode is true optional double ModelDuration 25 optional double Mode2TemperatureFactor 26 optional double Mode2Duration 27 optional int32 ProbabilityOfPropertyChangeOnly lt CHANGEONLY gt default 50 percentage optional bool PreserveVerticalRelationshipTest 29 default false optional bool PropertyChangeOnFixedCell lt PROPFIX gt default true optional bool SetOutputMisfits lt OUTMISS gt default false optional bool SetOutputCommonality lt OUTCOMM gt default false optional double Seed lt Seed gt optional int32 NumberOfIterations lt Number Iterations gt optional string log 35 where lt filename gt the relative or absolute path of the XML project file for the 3D GeoModeller inversion Case including the xml extension Note that a Case is a copy of an original 3D GeoModeller project this parameter points to the xml file of the c
91. change is assessed and on the basis of this assessment the proposed change may be rejected or accepted 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 127 Conients Help Top Contents Help Top lt 4 Back gt e if rejected the proposed change is simply reversed back to the preexisting values for that voxel and a new iteration begins with a new voxel selected at random if accepted the proposed change is kept and a new iteration begins with a new voxel selected at random The inversion process keeps a copy of the changing voxel model in memory but also maintains a file record of each accepted change to the voxel model Each accepted change is stored as a one line entry in a simple text file called modifications txt in the Case directory The entry records Which voxel changed To which new lithology if any To what revised physical property values The current iteration number is also recorded Note that you can monitor the progress of the inversion by using a UNIX tail command to see the last entry in the modifications txt file The command tail f filename executed in a second command window will scroll the progressively changing tail end of the modifications txt file in the command window Don t leave this command running it will affect the speed of the inversion The least squares misfit values the measure
92. change may in fact reselect the original formation The algorithm is described here The parameters in RunControl do influence the behaviour ChooseFrontierCell The aim is to find cells that are on a frontier between one geology unit and another We test if the voxel at i j k is 1 A frontier has at least one neighbor that is a different formation and 2 Not one of the cells fixed by SetFixedCells We then test if the formation has been set by the user as being completely fixed see CaseControl in which case the result is set to false We then test each of the voxels in the neighborhood looking for at least one of the neighbors having a different property law to the central voxel This test can be disabled by a false setting for AllowNeighbourPropertyDifferentCheck A frontier cell is one that passes these tests ComputeNewCell Contents Help Top There is nothing to stop the new lithology from being the same as old lithology The available voxels are those in face contact with the selected frontier cell Cells belonging to the AboveTopo lithology or formations that are not movable are excluded Cells that have a property distribution with zero spread parameter for example standard deviation for a Normal distribution are also excluded A random selection is made from the formations of the available neighbors and this formation is assigned to the chosen Frontier cell This constitutes most of the Markov Chain random wa
93. cify additional properties of the geology formations which will be used to control or limit the changes to geology formation boundaries that can be proposed during the inversion iterations Syntax SetLaw Specify the Properties of Geology Formations and specific details SetLaw Type 2 Inversion Control Properties of Geology Formations 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 54 Contents Help Top lt 4 Back gt IncludeBorderEffect In computing the model response of some discrete model there will always be edge effects The strategy used in 3D GeoModeller geophysical computations is to use padding around the model We expand the geology model by one model width in every direction by reflecting the model at the edges and corners of the model as illustrated in Figure 16 The method achieves a result which has smooth computed gradients at the edges of the actual model and the edge effects at the outer edges of the expanded model have negligible effect within the central area of interest The default behavior in 3D GeoModeller is to always include this border effect in the geophysical computations of the model In some circumstances the user may want to turn off this border effect Possibly for testing purposes OR The field data may be computed data from some other modelling package and may contain edge effects In these cases we m
94. d 0 01 ObservedGridList Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 94 Conients Help Top Contents Help Top 4 Back gt ObservedGrid type Gravimetry mean_elevation 50 precision 0 1 Match_Trend false Match_Trend Degree 0 Match_Trend_Rate 0 grid slab_inversion InputGrids slab_dipping Observed_Gravimetry ers ObservedGrid type Magnetism mean_elevation 50 precision 0 3 Match_Trend true Match_Trend Degree 1 Match_Trend_Rate 20000 grid slab_inversion InputGrids slab_dipping_Observed_Magnetism ers Example output Property Optimization Report Request to look at densities 0 Request to look at susceptibilities 1 Maximum absolute signal value to use in study spike removal 30000 000000 The International Geomagnetic Reference Field for this work Mag 44547 200000 X component 3347 640707 Y component 35348 519051 Z component 26902 203078 The number of formation layers considered in this work 4 The Observed trend matched geophysics grid used in this work Observed_Magnetism_2 ers The model response kernel geophysics grid used in this work layer 0 calculated_Magnetism_X_1 ers calculated_Magnetism_Y_1 ers calculated_Magnetism_Z_1 ers layer 1 calculated_Magnetism_X_2 ers calculated_Magnetism_Y_2 ers calculated_Magnetism_Z_2 ers layer 2 calculated_Magnetism_X_3
95. d but might produce a satisfactory constraint over the VolumeRatio values observed in the proposed models 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual Conients Help Top Interactive setting of Geology Shape Distributions m 74 lt 4 Back gt Definition Definition of the mode component Parameters Mean Standard deviation rStatistical law Rayleigh Weibull owo aes mso ows ao Seda r s Lithology specific settings Lithology Properties Slab E Fix lithology frontier Host Constraints Commonaility Veibull 0 0010 1 0 100 Commonality volume Normal 0 0 1 0 100 vA Shape ratio jNormal 0 25 0 05 100 Volume ratio jNormal 0 25 0 05 100 Always above these Lithologies E slab Host Stratigraphic Order Reset Here we have opened the third page of the wizard and then started to set a probability distribution function PDF for Commonality Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd lt 4 Back gt GeoModeller User Manual 75 Contents Help Top lt 4 Back gt Geophysical Forward Modeling Build and Revise 3D Geological Models with GeoModeller Fast Field Observations odeller generates model Introduce No Problem Introduce drillhole data Rapidly generate new models that honour the new data
96. d format to get this result nb Oasis Montaj does not support multi band grids and so cannot manage a tensor signal The Intrepid Visual tool Geophysics gt Visual also supports tensors grids so a fully exploration of all the possible enhancements can be made using that tool 3D GeoModeller MeshGrid support does not fully embrace the underlying Intrepid object oriented data object approach at this release It goes as far as vectors However we do expose the Intrepid tensor grids for forward modelling from a voxet especially the FFT method The dyke modelling also includes the ability to handle full tensor data as a tensor Improvements will be progressively made here As the number of observed parts of the field increases the process of driving the inversion towards a most likely convergent model takes correspondingly longer The stochastic solver tends to scale in a linear fashion as more components are added The philosophy for the scalar case is to spend 50 of the time on the property law and 50 of the time perturbing the geological unit boundaries The question to ask is can we maintain this ratio and somehow optimize honoring the full tensor signal and the model convergence Recent work by Intrepid on tensors develops the notion of separation of concerns This has lead to a patent for preparing the survey data for interpretation via a gridding SLERP and curvature integrity smoothing process MITRE Approximately half the useful signa
97. d Topography Considerations In addition to the many general considerations for all types of geophysical grids above for gravity data it is important to consider what processing has been applied to the data and what are the implications in relation to how topography should be modelled Free Air gravity is a gravity dataset for which only the Free Air correction has been applied this correction simply adjusts the response for variations in separation between the observation and the mass of the Earth concentrated at a point at its centre For Free Air gravity the component of signal which is due to topography is still contained in the data The reduced downwards pull of gravity due to hills of mass above the observation or valleys of air below the observation has not been corrected for Since the observed data contains this effect the corresponding computed model data must reproduce that so the topography should be modelled as follows Contents Help Top With the NewCase command set the lt zMaxVoxet gt value to be at or above the highest point of the topography this is a default behaviour Use SetUseTopo meaning use the topography IncludeBorderEffect The default is to use the topography In batch use the SetAboveTopoDensityLaw to specifically assign the density of the region above the topography to be zero density SetAboveTopoDensity You must specifically use this command to set this value beca
98. d in the table below 3D GeoModeller computes geophysical responses in terms of the units noted in the table and so the observed geophysical grid data must be supplied in terms of these same units For unit conversions see Appendix 1 Units and Units Conversions Allowed grid file formats ERMapper ers Geosoft grd ASCII semi and others that maybe be added from time to time Do not use an image here The geophysics grids must contain proper signal strenth amplitudes and frequencies that are directly from a geophysical survey A byte grid cannot be used Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual Conients Help Top Contents Help Top 44 4 Back gt This table shows the geophysical data types and units allowed in 3D GeoModeller joint Gravity and Magnetic Inversion Data type Units Description and key word Gravimetry mGal Conventional gravity data as measured using a Z downwards frame of reference Since the Z downwards direction is determined by the gravity vector itself conventional gravity is total gravity field strength Ge Gn Gd mGal Vector components of gravity data where e east n north and d down in a right hand coordinate system Gee Gen Ged Gnn Eotvos The components of the gravity gradient Gnd Gdd tensor Magnetism nT Conventional total magneti
99. d to specify a reference geology model the Reference Lithology Voxet This reference geology model is used by the commonality tests Notes This command updates the inversions xml file This is the all important file that contains all the process instructions for your current case and run The Reference Lithology Voxet can be any Voxet which has the same dimensions as the Voxet geology model being inverted and which has a field called Lithology where the Lithology field contains only integers in the range 0 n corresponding to the 0 n lithology entries listed in the inversions xml file The default if not explicitly set by this command is the Case Voxet the voxel geology model created by the NewCase command See Figure 18 top Itis not uncommon to continue an inversion Run from say the end of an earlier Run For this case the Initial Voxet would be derived from the final iteration of the earlier Run but the Reference Lithology Voxet might be set explicitly with the SetReferenceLithology command to be the Initial Voxet of the earlier Run In this way the commonality tests for the restarted Run would continue to be with reference to the original starting model of the earlier Run See Figure 18 bottom e Whilst the above two examples are typical the Reference Lithology Voxet may be any appropriate Voxet possibly even constructed using third party software Comment Commonality Tests The commonality tests are one o
100. dedination Reman magnetis stion app An example table of Rock Properties for a study Figure 6 3P 2D Geophysics Cross sections s100000N Gravity on s100000N 1of1 Gravity Magnetic Seismic Gravity Profile 7 Compute Gravity x 3 Observed Grid 2 8 a 8 Physical Properties Partially Defined e Computation Parameters 8 Number of Stations 10 Computed Anomaly mGal 8 8 Length of Profile 1 2 Extension 15 Sane a aa A Constant Elevation o 5 000 10 000 15 000 20 000 25 000 30 000 35 000 40 001 On Topography Distance m Drape gt Height above Terrain I Computed Gravity Effect Geology Cross Section 1520 0 s00 1380 0 2800 0 f 4240 0 Depth m 5680 0 7120 0 8560 0 10000 0 O 2400 0 72000 120000 188000 216000 264000 312000 300000 Distance m PalaeoMarker Proterozoic Cover W Basement LPalaeozoic W LateGranite1 M Mesozoic W Miocene m UPalaeozoic Example of a section 2D forward model in a working project showing the geology and gravity response Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 21 Contents Help Top lt 4 Back gt Forward Modelling Wizard Of course you must have a geology model before you can proceed to use this opti
101. difications txt file By sequentially reapplying the changes up to the required iteration number the Geology Model Voxet that existed at that point of the inversion is regenerated Create a RunState situation for an inversion run using the specified file generate the voxet for a model that was created at a specific point in the evolution message RunState_GMT required string filename lt CaseXML gt required string run lt Run gt required int32 number_of_iterations lt Iteration gt optional string case 4 Contents Help Top where lt CaseXML gt the relative or absolute path of the XML project file for the 3D GeoModeller inversion Case e lt Run gt an alphanumeric string or identifier that identifies the inversion Run lt Iteration gt the iteration number for which point the Geology Model Voxet is required e lt OutputDirectory gt the relative or absolute path of the output directory which must exist The output filename is generated automatically lt Case gt lt Run gt lt Iteration gt vo The output is a Geology Model Voxet it has the same fields and other attributes as the initial and final Voxets created by an inversion Run For example 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 144 Contents Help Top lt 4 Back gt InversionTask RunState filename InputGeology slab_vertical_2
102. dilation Closing is the reverse sequence a dilation followed by an erosion This process attempts to restore the original area of features but with some rearrangement of the boundary pixels The default application of the homogeneous morphological filter is to use the pre defined structural element CUBE_3x3_FACE_EDGE_VERTEX 1 The operation is performed by default every 5000 iterations The complete description of the default homogeneous filter application is There is a random 50 50 probability of applying an opening or closing operation There is a random choice of which lithology the operation will be applied to There is a random choice of which direction the filter is applied N S E W up down 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 149 Contents Help Top lt 4 Back gt HomogeneousFilter Contents Help Top The HomogeneousFilter option in the RunControl task specifies the structural element to be used in the homogeneous morphological filter operation The Allow Homogeneous Filter RunControl command sets whether the homogeneous filter operations are performed This is an historic control not normally encouraged any more RunControl message HomogeneousFilter_GMT required int32 Rate lt Rate gt default 1000 optional bool Allow lt Allow gt default true where lt StructuralElementName gt is the name
103. e following task You can then use these results to quantify uncertainty of a heat resource in the ground during studies into geothermal prospectivity work Use 3D Geomodeller Import gt 3D Grids gt 3D Voxets to explore then add to your existing MeshGrid datasets for examining the statistics and visualizing the results Protobuf Example InversionTask MakeParameterSweepSummaryStats testArea_2suites_imported testArea_2suites_imported xml filename Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 89 Contents Help Top lt 4 Back gt case Case_1 output_stub_name stochastic_ statistical_voxet testArea_2_uncertainty vo ReportFile stats_report rpt BoundaryConditionToSweep location Base BoundaryStyle Boundary HeatFlow LithologyPropertyToSweep lithology aboveC property ThermalConductivity LithologyPropertyToSweep lithology ZtoC property ThermalConductivity LithologyPropertyToSweep lithology BLS property HeatProductionRate LithologyPropertyToSweep lithology granites1 property HeatProductionRate Number Permutations 2 Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 90 Conients Help Top 4 Back gt ForwardModelFromDykes Contents Help Top This is new to
104. e Reference Lithol ogy Model red arrow bottom SetLaw Specify the Properties of Geology Formations The CaseControl SetLaw sub tasks are used to specify the various properties of the geology formations For each property a property law describes the distribution of values for that property for a given formation There are two types of properties of formations that must be defined The physical property data for geology formations such as Density and Susceptibility A formation may have mixed lithologies their relative abundances specified by percentage Special inversion control properties of formations which can be used to implement geology constraints which influence the lithology changes that can be made during an inversion Run For example the ShapeRatio property of a formation specifies the degree to which the ratio of that formation s surface area to volume must be maintained during an inversion Run This is the start of a big subject how to reasonably constrain the geology nature of my model while allowing stochastic process to alter boundaries properties etc No geology constraints quickly leads to destroying any semblance of coherent bodies or strata in your model So clearly there needs to be rules devised to constrain things The original hard geology facts such as surface outcrop structural trends stratigraphic order come to mind Up to the present other available tools use concepts such as the
105. e properties of the present model and the Reference model The latter may or may not be the same as the Initial model depending on the user settings Commonality is defined as Possessing like and interchangeable characteristics The number of voxels in common between the proposed models and the reference model is controlled statistically using a Commonality constraint The following diagram illustrates to intersecting cylinders that share a common portion Figure 25 Commonality determination for intersecting cylinders Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 113 Contents Help Top lt 4 Back gt The following image is from page 3 of the Inversion wizard where the user has the Lithology specific settings Lithology Properties E Fix lithology frontier Commonality Veibull 0 0010 1 0 100 2 Commonality volume Normal 0 0 1 0 100 Shape ratio JNormal 0 25 0 05 100 2 Volume ratio JNormal 0 25 0 05 100 option to design and specify probability functions for each of the possible 4 methods of imposing shape volume constraints on the geology By choosing the pencil button you are then given the chance to change the probability function Note that a Gaussian law is not offered as this would imply the current geology is 50 likely to be wrong The decision as to which of the tests to actually use is deferred to p
106. e root of volume for example specifies the degree to which an inversion Run must maintain the ratio of a formation s surface area to volume The set of one or more geophysical grids to be used All grids must have exactly matching grid cell size and positions Associated parameters the height of observation for each dataset must be specified and for magnetics data the Earth s magnetic field intensity inclination and declination are required for computation of magnetic responses 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 39 Contents Help Top lt 4 Back gt NewCase The NewCase command sets up a new inversion Case which will then be used as the basis for a set of one or more Runs Formal Syntax for creating in batch invbatch batch lt taskfile task gt where lt taskfile task gt contains NewCase filename lt Project gt case lt Case gt x_cell_ size lt xCellSize gt y_cell_size lt yCellSize gt z_ cell size lt zCellSize gt east_minimum_voxet 0 000000 east_maximum_voxet 1000 000000 north_minimum_voxet 0 000000 north_maximum_voxet 1000 000000 elevation_minimum_voxet lt ElevationMinVoxet gt elevation_maximum_voxet lt ElevationMaxVoxet gt ObservedGridList ObservedGrid type Magnetism mean_elevation lt MeanElevation gt compute_surface_style ConstantElevation precision lt Precision gt Match
107. e the general tendency of the boundaries to become increasingly complex See more notes at Homogeneous Morphological Filter There are a series of RunControl commands relating to the definition and use of morphological operators The effectiveness of the morphological operators is currently being challenged Our present experience suggests that other controls such as Commonality and ShapeRatio are proving to be more effective constraints for maintaining geologically reasonable shapes and geology boundaries Current recommended practice is to not use the morphological operators The morphological operators are off by default Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt 146 4 Back gt GeoModeller User Manual Conients Help Top Note that the morphological filters allow the complete elimination of a unit This would occur if a proposal that would eliminate the last voxel assigned to a particular formation is accepted Figure 28 Homogeneous Filter Type Choose Filter E oa eaten Open erosion then dilation Close dilation then erosion Erosion Dilation Choose direction E W N S Up Down Apply Filter Identify Voxels with modified lithology Reset the counter for the number of acceptances since the filter last applied Erosion Dilation Counter or Homogeneous Counter Morphological Filter Scheme Contents Help Top 2013 BRGM amp Des
108. e the velocities for each unit for which have observations e You can also choose to convert the velocities to an estimated density and then calculate a gravity response This can then be compared to any surface gravity observations you may have This process is very useful in independently validating the main geology picks from the seismic sections e Unconstrained kriging can also be used to interpolate in 3D your velocity or density estimates from the 2D seismic data This is a much more problematic approach as you are ignoring any breaks in the rock fabric The conversion of velocities to densities is often done by a simple equation This is easily done using the MeshGrid fields and the equation builder functions Support for a table lookup to convert and or a spatially based equation is also supported Below is an example of a 2D seimic section predicted by assigning velocities to each unit then doing a forward model on a section You can get radically different results by changing the sample spacing and time sampling so this provides a simple way to appreciate the impotance of survey design parameters vs the seismic data predicted vs the geology scenario It is easy to say commission a survey that in fact does not lend much new knowledge to the deeper strata and the rock relations Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 35 Contents Help Top lt 4
109. eRatio ProbabilityDistributionFunction type Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual Conients Help Top LogNormal mean 0 0 stddev 0 05 LithologyProperty lithology LogNormal mean 0 0 stddev 0 05 LithologyProperty lithology LogNormal mean 0 0 stddev 0 05 LithologyProperty lithology LogNormal mean 0 0 stddev 0 05 LithologyProperty lithology 73 q Back gt SedMiddle property ShapeRatio ProbabilityDistributionFunction type SedLower property ShapeRatio ProbabilityDistributionFunction type Basement property ShapeRatio ProbabilityDistributionFunction type Mantle property ShapeRatio ProbabilityDistributionFunction type LogNormal mean 0 0 stddev 0 05 Contents Help Top Shape is defined as the dimensionless number square_root boundary_counts cube_root volume_counts where boundary_counts is the number of faces of voxels occupied by a particular formation that are in contact with voxels of another formation Note that the RunControl parameter settings IncludeAboveTopoFacesInShapeRatio and IncludeOutsideFacesInShapeRatio control whether voxels in contact through a face to a voxel of the AboveTopo lithology or voxel faces forming part of the outside of the mesh contribute to the boundary_count volume_counts is the number of voxels occupied by the par
110. ea observations from the mapping module using the geological Most probable 3D observations map produced from the inversion module using the geological and geophysical observations Relationship of geophysical inversion methods to geology Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 15 Contents Help Top lt 4 Back gt Detail Outline of the Inversion Algorithm in 3D GeoModeller The inversion algorithm can be defined using 14 steps 1 Build the a priori geological model 2 Define the a priori physical property laws 3 Specify any a priori geological constraint properties for each unit such as those that are required to maintain the volume and shapes of units 4 Discretise the model to a voxel based lithologic model 5 Specify a priori fixed voxels the lithology of which may not be altered eg the mapped surface observations 6 Make a list of the geological boundary or frontier cells 7 Compute a unit response kernel for the gravity or magnetic field or their tensor components for each voxel at each observation location 8 Property optimization step to hone in on bulk lithology properties that join the geology to the observed geophysics 9 Initialise the distribution of density magnetisation remanence and geological constraints on the basis of voxel lithology 10 Compute the geophysical effects of the model 11 Select a voxel at random
111. ecomupting the kernel responses and saving these in memory for re use trial confirm a near linear reduction in elapsed time versus the number of Nodes Multi threading of the calculations is also being used Check Point Restart has been implimented so that more flexibility on managing simulations is achieved Control over this aspect is yet to reach this language equivalent way to specify INTREPID_NODES 16 is via the delagate command message Run_GMT required string filename lt CaseXML gt required string run lt Run gt optional string case lt Case gt optional bool Testing lt Testing gt default false optional bool do_MPI lt MPI gt optional Delegate_Process Delegate 6 not really used at present optional int32 Number_CPUs lt CPU gt default 1 here is the way to get more CPUs into the act optional string ProcessID_Log 8 optional int32 checkpoint_iteration lt CHECK gt default 0 write a checkpoint every N iterations optional bool SaveForwardResponsePerLithology lt RESPONSE gt default false used in property optimization produces an ers grid for each lithol ogy optional string log 17 where lt CaseXML gt the relative or absolute path of the XML project file for the 3D GeoModeller inversion Case lt Case gt an alphanumeric string or identifier that identifies the Case to be executed 2013 BRGM amp Desmond Fitzgerald amp Assoc
112. el eg observed arun can explore propability space for a prescribed number of iterations and then be restarted if required A response kernel is the unit response of each prism to a property change e For gravity a grid is produced for each lithology that contains that units response at the field observation plane e For magnetics a vector response is produced as 3 grids X Y Z A reference voxet also contains response kernel information Create a Run situation for an inversion run using the specified file Il formal definition of a RUN a run has specific controls set within the confines of the more general case arun can hold the geology constant and just perturb the properties arun can force the stochastic process to reject overturned geology for certain units arun can select from all the possible topological operators what mix and what variation to allow arun can impose a set of fixed or unchangeable parts of your geology model eg observed arun can explore propability space for a prescribed number of iterations and then be restarted if required Extenions to Run in a super computer or Cluster situation the idea is is to have a Master process that distributes the geophysics forward modelling aspects to many SLAVE nodes and also breaks up the domain into vertical slices As we are using spatial prism based methods for calculating the response efficiencies are mostly got by pr
113. eld strength inclination and declination The Geophysics Types to be computed Gravimetry Gee Gen Ged Gnn Gnd Gdd Magnetism Me Mn Md Mee Men Med Mnn Mnd Mdd e The elevation at which the geophysical response is to be computed Whether to include the border effect This is typically set to 1 Yes Contact us for an example Parameter Sweep Studies of Potential Fields Contents Help Top Also so far only in batch you can perform uncertainty estimations on a regional scale for gravity and magentic field responses A parameter sweep automatically creates many connected scenarios each of which is run on one or many computers in a 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd lt 4 Back gt GeoModeller User Manual 83 Contents Help Top lt 4 Back gt cluster This was established initially for geothermal sensitivity modelling All elements of the simulation can be perturbed so that typically either boundary conditions or physical properties such as density and susceptibility for the important units are cycled through at least 3 states making a combination of simulations that constitutes a stochastic study of the uncertainties A final pass gathers all the results and produces statistical population in a voxet with the potential variability for each cell An example for Heat is presented in the following section ForwardModelTemperature Wizard Heat in 3D New to v2012 is capabili
114. en given the tag ThermalUncertaintyStudy This syntax for this sub task can be work out by examining the lexicon for this command The parameter sweep can be run to generate the family of tasks and the report produced shows all the property permutations When using 2 states the property used is plus minus the standard deviation from the mean The third case adds in the mean as well Example Output Report Doing a thermal uncertainty simulation Case_1 Sweep 2 properties 1 std_dev 1 std_dev Requested Lithology Property Mean Std Deviation to sweep aboveC ThermalConductivity 2 0 2 ZtoC ThermalConductivity 1 4 0 2 BLS HeatProductionRate 1 1le 005 1 5e 006 granites1l HeatProductionRate 8e 006 3 5e 006 Requested Boundary Conditions mean Std Deviation to Sweep Perturb Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 88 Conients Help Top lt 4 Back gt Base Boundary _HeatFlow 0 036 0 005 Total number of permutations 32 Starting Heat Flow work aboveC ZtoC BLS granitesl Base Boundary HeatFlow 1 1 8 1 2 9 5e 006 4 5e 006 0 041 2 1 8 1 2 9 5e 006 1 15e 005 0 041 3 1 8 1 2 1 25e 005 1 15e 005 0 031 4 1 8 1 6 9 5e 006 1 15e 005 0 031 5 1 8 1 6 1 25e 005 1 15e 005 0 041 6 2 2 1 2 1 25e 005 4 5e 006 0 041 7 2 2 1 6 1 25e 005 4 5e 006 0 031 8 1 8 1 2 1 25e 005 4 5e 006 0 031 9 1 8 1 6 1 25e 005 4 5e 006 0 041 10 2 2 1 2 1 25e 005 1 15e
115. ensity susceptibility heat production rate heat flow and velocity values and statistical laws are required Once you supply these representative values 3D GeoModeller can then predicte the response An important point to note is that 3D GeoModeller is only going to show you the response from the model that you have not included Most potential field geophysical datasets that you may have access too will also have signal content from deeper sources than your model To properly compare Apples with Apples you should then estimate and remove the effect of these deeper sources from your observed data This is typically done using grid based Fourier filtering techniques Sometimes the effect of high terrain variability makes the direct comparison of forward models with observations more difficult You could consider using a vertical derivative rather than the field itself to aid this process In the case of potential fields as we are dealing with predicted anomalies in the field it is the curvature of the predicted field versus the observed curvatures that are the primary measure of goodness of fit 3D GeoModeller calculates a forward model by first discretising the 3D geological model to a voxet or 3D grid Each cell is given the appropriate mean property for its geology and a summation of all the contributions to the required components of the observed field is carried out In the case of the 2D forward model of a seismic section you a
116. ent below the voxel location The number of PreserveVerticalRelationship tests and rejections are reported in the lt Case gt _ lt Run gt rpt file and in the RunResult block of the inversions xml file The PreserveVerticalRelationship properties are recorded in each Lithology block of the inversions xml file as shown below Only entries of 1 are included explicitly in the inversions xml file Hence the example below from the XML file corresponds to the CaseControl gt SetLaw gt lithology Chilitos_Formation_Mafic_Unit_B node false false false false false false true true lt Lithology Formation Chilitos_Formation_Mafic_Unit_B gt lt PreserveVerticalRelationship ExcludeBelow Triassic_Jurassic_Unconformity gt lt PreserveVerticalRelationship ExcludeBelow Zacatecas_Formation gt lt Lithology gt Contents Help Top A CaseControl SetLaw PreserveVerticalRelationship command with fewer entries than computed formations will be processed assuming that the remaining entries are false Any entries of a CaseControl SetLaw PreserveVerticalRelationship command in excess of the number of computed formations will be ignored 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 122 Contents Help Top lt 4 Back gt Fixing parts of your model the SetFixedCells The SetFixedCells command is used to fix the lithology of specified voxels in the 3D geolog
117. ents Help Top 4 Back gt Figure 12 Simple slab model to illustrate principles of inversion You have even in this simple case a geometry and the need to specify properties Physical Properties The specification of the physical properties of each geology formation can either be predefined in the 3D GeoModeller Project or can be set later by using CaseControl commands The NewCase command records the physical property settings or their default values in the inversions xml file of the Case Likewise the specification of the Reference Density may be predefined in the 3D GeoModeller Project or left at its default setting 2 67 g em gt The density for each voxel in the geology model relative to the Reference Density determines a density contrast for that voxel from which the model s gravity response is computed The Reference Density should typically be that density value used for the Bouguer data reduction of the observed gravity data if Bouguer gravity data are supplied or the mean density of the region if Free Air gravity data are used The NewCase command records the Reference Density in the inversions xml file of the Case Use the CaseControl commands see CaseControl to further modify these physical property data for the Case Surface Topography The surface topography for the project area is sourced from the 3D GeoModeller Project Note that 3D GeoModeller describes modelled geology interfaces that extend
118. ers used in the voxelisation of the geology model are determined from the supplied grids The content of these dummy grids however can be anything or simply zero The content is never used for the ForwardModelFromCase command Only the geographical parameters of the grids are used See more on these geographical considerations in Gravity Dataset and Topography Considerations Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 81 Contents Help Top lt 4 Back gt Alternatively use the ForwardModelFromProject command to generate a forward model geophysical response directly from a 3D GeoModeller Project Note that the default is to include the border padding models when computing the response For a batch example invbatch batch mytaskfile task ForwardModelFromVoxet The ForwardModelFromVoxet computes the geophysical responses of a nominated Geology Model Voxet This can be any voxet including ones coming from other complimentary products such as GOCAD Oasis Gemcom Vulcan The prime requirement is that the voxet contain a lithology field that can be interpreted as a discretization of the geology model Also Intrepid must have an appropriate driver to read the binary data properly These drivers are constantly being added too Batch example InversionTask ForwardModelFromVoxet uses vfilt to run via FFTW also compatible with the 3D
119. ersion Case XML file generated directly from the schema for a fully populated example of the file The 3 phases of all processes are The majority of the commands in this manual are Edit actions There is the main Run command which typically takes all the computational time The last phase is to Query the results making movies snapshots and other reports As an aid each command in the following sections is classified as belonging to one of the above categories 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd lt 4 Back gt GeoModeller User Manual 36 Contents Help Top lt 4 Back gt Statistical Laws amp Probability Distribution Functions Contents Help Top At the heart of much of the thinking in 3D GeoModeller Inversion is a set of stochastic processes that respect statistical models The main potential field interpolator in 3D GeoModeller is based upon universal dual kriging and as such represents a high level of geostatistics The models that govern allowable changes in the volumes of geological bodies are constrained to follow Exponential or Log Normal distributions Finally the lithological properties that you are required to specify for all your rock properties also respect laws such as Normal Lognormal Each of these models has a well defined and well understood mathematical basis The following diagrams represent normal and log normal probability distribution function
120. es 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 109 Contents Help Top lt 4 Back gt Temperature We introduce the term Temperature Entropy in the context of influencing the behaviour of the solver The idea here is to allow for a coarse initial performance of the solver s acceptance on a new randomly generated proposition that does not seemingly improve on the current position The Markov Chain Monte Carlo approach has us accept on a random basis propositions for a new state that are not better than the existing one so that we do not get caught in false valleys in the quest to reduce the overall mis fit between the observed datasets and the inverted model results Temperature is the term we use to allow for a relaxed initial quest to get an accelerated convergence to a point where the mis fit never really improves This state is then the point when the real exploration of probability space can begin in earnest and when we should reduce the Temperature or Entropy of the system so we do not spend too much time on very unlikely degradations of the likelihood of the proposed change being for the worst now but ultimately for the better as things continue to evolve The lack of a perfect fit is really a reflection of the accuracy or precision of the original observed geophysical dataset as well as the resolution of the geology model l oP hace Soer Parameter pm
121. es It also focuses outcomes from this process so that geologists with different backgrounds when presented with the same observations will derive similar 3D geological interpretations These interpretations are quantified using the principles of geostatistics and a geological rules engine In many situations you the geoscientist face the reality of sparse data Gravity or aeromagnetic datasets Shuttle Radar satellite digital terrain SRTM topography are likely to be the largest non geology mapping source of data This manual describes how a structural geology controlled 3D model can have its geophysical response estimated in 2D and 3D The rock properties and field conditions needed to achieve this objective are added Gravity Magnetics Heat and Seismic response are all estimatable 3D GeoModeller provides both forward amp inverse geophysical modelling to test and refine your 2D 3D geological interpretations Geophysical Forward Modelling 3D GeoModeller is able to generate various predicted geophysical responses or forward models from the 3D geological model you have created Typically you are interested in the model geophysical signature at either the ground surface or at a drape surface above the ground that represents a flying height The types of forward model that 3D GeoModeller can produce follow from your ability to ascribe representative lithological properties to each and every Geological unit in your model Typically d
122. es do check neighbour properties Recommend set 0 no lt MISRMS gt SetLargeMisfitRMSThresholdFactor lt value gt parameter adjust the likelihood function for acceptance tests lt MISTEMP gt SetLargeMisfitTemperature lt value gt parameter adjust the likelihood function for acceptance tests lt TrendGrids gt SetOutputTrendGrids lt true false gt NB Written to a subdirectory of lt CaseDir gt call TrendGrids_ lt Run gt lt DUALMODE gt SetDualTemperatureMode lt true false gt This allows for early accelerated exploration of uncertainty space to speed the solver up model TemperatureF actor model Duration mode2 Temperature Factor mode2 Duration default 0 1 100 1000000 99900 Initialise the lithology and physical property voxets for use in the Run LithologyInitialiseStyle lt FromModel FromVoxet lt initialLithologyVoxetPath gt gt DensityInitialiseStyle lt FromLawRandom FromLawMean FromVoxet lt initialDensityVoxetPath gt gt SusceptibilityInitialiseStyle lt FromLawRandom FromLawMean FromVoxet lt initialSusceptibility VoxetPath gt gt RemanentMagnetisationInitialiseStyle lt FromLawRandom FromLawMean FromVoxet lt initialRemanenceVoxetPath gt gt Morphological filter configuration SetHomogeneousMorphologicalFilter lt StructuralElementName gt set one of the predefined structural elements SetDilationOrErodeMorphologicalFilter lt StructuralElementName gt set one of the
123. es is via their volume This is an easier and more tractable attribute to track than the surfaces of the units The two preferred ways of measuring the evolution of geology bodies are Commonality how similar is my current volume to the one I started with Shape ratio how similar is the surface area volume now to what I started with You are able to use one or both of these measures to constrain the uncertainty you might have about parts of your model to a defined behaviour Of equal importance to your geological model are the property laws you must propose for each of your units 3D GeoModeller allows you to propose combinations of statistical laws for each unit in your model For instance a Gaussian bi modal density distribution for one of your rock units can be proposed to cover the case where you know you have a certain percentage of higher density material in a particular unit The process of inversion may then show you local concentrations of this higher density material within that unit enabling you to explicitly model that sub unit if you need too Geoscientists are plagued by a legacy of poorly sampled and understood lithological properties and inversion is one place where we stand exposed by this Proposing 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 8 Contents Help Top lt 4 Back gt geological unit bulk properties that are too free or have a high variabili
124. f the mechanisms for setting geological constraints which are designed to limit the geology voxel model changes that can be proposed such that the evolving geological model always remains a realistic geology model This geological realism is achieved by specifying that the progressively changing inversion geology model must maintain some reasonable degree of commonality with reference to a specified Reference Lithology Voxet For more details see SetLaw Type 2 Inversion Control Properties of Geology Formations specifying the degree of commonality this is a setting of a property law e AllowCommonalityTest In batch the CommonalityVolume is a geology test that can be applied during the inversion to jointly control the number of voxels assigned to each formation and the number of voxels that this formation has in common with the distribution for this formation in the reference model turning on the commonality tests Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 59 Contents Help Top lt 4 Back gt Figure 18 Examples of the Reference Lithology Voxet The default is to use the Case Voxet for both the start of an inversion Run and also as the Reference Lithology Model top Another scenario could be to use the Voxet from the end of a previous Run as the start of a new Run green arrow but to use the original Case Voxet as th
125. fore commencing a full scale inversion you are fully conversant with the simple slab inversion tutorial and all its variations See Appendix 4 Simple Slab Example for some of this work Tutorial E is the dedicated resouce to cover the material carefully Geologists also like to test their 3D models by systematically withdrawing each original observation of the geology You then recompute all of your model and save off the surfaces and volumes for comparison with what you get from other cases The idea here is to test how adequately sampled your model is and also how sensitive it is to any one observation This process may be described by some as Geological Inversion The great strength of the underlying 3D GeoModeller compute engine is its ability to estimate a third dimesion in geology from the surface structural observations We complement this by using the independent potential field geophysics to constrain the largest part of the uncertainty in your model Quantifying Uncertainty Contents Help Top The uncertainty you have in defining 3D geological bodies can be quantified and characterized in many ways and by using a variety of approaches With this release there exists tools for parameter sweep property optimization using least squares best fitting tagging every observation with an error estimate and rock properties all having a probability distribution function The best way to get a handle on individual geological bodi
126. from a 3D grid of an interface of a field output to standard surface format as triangles used for iso surfaces in inversion grade boundaries in kriging message MakeSurfaceShells_GMT required string inputvoxet lt Voxet gt required string inputfield lt Field gt required string operand lt Operator gt gt lt gt lt or LE GE INSIDERANGE optional double isovaluel lt Value gt optional double isovalue2 lt Value gt optional string output lt OutputFilename gt default outputDS where lt Voxet gt any 3D project voxet which is derived from the 3D GeoModeller Project lt Field gt a Keyword as used in the voxet header file such as Lithology MostProbable MostProbableThresholded MeanDensity StdDevDensity Probablity0 Probablity1 lt Operator gt lt LE GE INSIDERANGE gt less than or equal greater than or equal e lt Value gt is an iso value of the Field to be used in conjunction with the lt Operator gt to define some 3D region of interest within which the Field has a specified value or range of values such as Lithology 2 Density gt 2 1 e lt OutputFilename gt the filename of the output mesh and optionally the relative or absolute path of the output directory which must exist For example InversionTask MakeSurfaceShells filename StatsReports Shell_Case_2_Run_1_SSS_80_MeanDensity GE_Opt1 xml case C
127. g comprised of metasediments and denser more magnetic amphibolites Thus the statistical law for a geology formation physical property may specify the mean standard deviation and percentage abundance for up to three component lithologies For example a density property defined as Normal 2 66 0 05 70 Normal 2 80 0 05 30 specifies a normal distribution but bi modal with 70 of samples in one population with mean 2 66g em and 30 with mean 2 80 glem The standard deviation for both is 0 05 g em Normal 2 66 0 05 100 specifies 100 with mean 2 66 g cm and standard deviation of 0 05 g cm Of course it is possible to use inversion to isolate a body without an initial model of that body being posed The observed geophysics can drive the creation of such a daughter body within a unit provided you allow for a mixed lithology Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 64 Conients Help Top Contents Help Top 4 Back gt Physical Properties Use a Small Standard Deviation In specifying the physical property values of geology formations often based on very little information it is recommended to constrain the standard deviation to a relatively narrow range rather than allow a wide variation of property values A set of physical property measurements on core samples will typically exhibit a wide variation mainly bec
128. g individual properties or geometries A close starting model ensures you maximize the likelihood and minimize the time needed to explore the relevant part of probability space to firstly converge to an acceptable misfit and then continue through gathering good statistical results Taking the example case of having an observed gravity grid and a forward model of the gravitational response from your model you should immediately examine the two grids for a spatial comparison A histogram provides a way to examine the statistics as shown in Figure 11 Figure 11 Illustration of a non viable reference model prior to any inversion The left hand popu lation from a forward model of the gravity response is a completely different distribu tion to the observed response The average starting misfit is more than 200 mGal horizontal axis and far too much to consider inversion In the situation shown the likelihood of your starting position migrating to the required observed position while also honouring the known constraints is very low It is for this reason you are advised to continue working on improving your starting or reference model This is done by looking at problem areas via sections making changes and updating the 3D forward modelling To retain realistic geological bodies you are advised to make use of volume and shape ratio constraints A full explanation of the workings of these follow If this constraint is not used an apparent c
129. gy field lt InputLithologyField gt string property field lt InputPropertyField gt int32 number_of_bins lt NumberOfBins gt ScaleOption_GMT Scaling lt ScaleOption gt string report lt OutputReport gt optional string products 10 use this for forward modelling to find output voxets optional string log 17 Contents Help Top where lt CaseXML gt the relative or absolute path of the XML project file for the 3D GeoModeller inversion Case lt Voxet gt any 3D project voxet which is derived from the 3D GeoModeller Project the Voxet must contain a Lithology field lt InputLithologyField gt a Keyword as used in the voxet header file such as Lithology This field is used as the Lithology field used to group the statistics lt InputPropertyField gt a Keyword as used in the voxet header file such as MeanDensity StdDevDensity The histogram is primarily intended for reporting the distribution of real vales such as Density and cannot be practically applied to fields like MostProbable lt NumberOfBins gt is the total number of bins to be used for generating the histogram lt ScaleOption gt lt LinearOrLog gt lt minClip gt lt maxClip gt where e lt LinearOrLog gt 0 for Linear and 1 for Log lt minClip gt minimum value or use Auto to have the software automatically calculate this lt maxClip gt maximum value or use Auto to have the s
130. hangeOnFixedCell 0 no do not change properties Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 108 Conients Help Top Contents Help Top 4 Back gt AllowNeighbourPropertyDifferentCheck The default for AllowNeighbourPropertyDifferentCheck is false In performing lithology boundary checks this default setting allows for the properties of the two neighbouring voxels to be checked If the properties of the two voxels are the same it is determined that there is no effective boundary between those two voxels and so any boundary perturbing option could not be proposed for the target voxel This is the default behaviour and has been traditionally the behaviour in 3D GeoModeller inversion In essence this was saying the properties are the same therefore inversion can have no opinion about the position of the boundary between these two lithologies With new constraining parameters providing improved controls on the progress of the inversion there is less need for this restriction Thus the present recommendation is to turn off this setting Recommend AllowNeighbourPropertyDifferentCheck 0 off No do not check the properties With this setting if the lithology of two neighbouring voxels is different then it is accepted that there is a lithology boundary between the two and boundary perturbing options can propose lithology chang
131. he grid edges The second to last panel lets you set the geophysical properties if you haven t already done so in 3D GeoModeller The last panel lets you run the forward model The Number of Cores is only relevant for spatial forward modelling If you have a computer with multiple CPUs Cores you can set the number of cores that 3D GeoModeller should use to speed up the forward modelling im t om obs_Gravity calculated_Gravimetry_1 Initial Misfit Comevted Rega Trend Regional Trend Computed Regional Trend The results window shows the following Bottom row left regional field that you can set or let 3D GeoModeller solve for the best fit to the observed data Bottom row centre the calculated model response Bottom row right the misfit once a trend is removed Upper row left the observed field Upper row centre the final model sum of computed response and regional Upper row right misfit between observed and model Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 78 Conients Help Top 4 Back gt Forward Model from Project batch Contents Help Top ForwardModelFromProject lt eCellSize gt lt nCellSize gt lt zCellSize gt lt EastMin_Voxet gt lt EastMax_Voxet gt lt NorthMin_Voxet gt lt NorthMax_Voxet gt lt ElevationMin_Voxet gt lt ElevationMax_Voxet gt lt Elevation gt lt IGRF gt lt
132. his new model is stored The inversion returns to Step 11 and continues to iterate around this loop An ensemble of models that satisfy geological constraints and can satisfactorily explain the geophysical signature might be explored by continuing for a further million iterations Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 16 Contents Help Top lt 4 Back gt In a variation of the inversion sequence we can also choose to use some iterations at Step 11 to homogenise the current model This uses morphology based operations applied to geological boundaries to add or remove voxels from the boundaries of features in order to smooth them to join separated portions of features or separate touching features and to remove isolated voxels noise from the model The following flow diagram is the simplified strategy used to calculate the lithologically constrained inversion process The Monte Carlo philosophy dictates that sometimes when a modification fails its acceptance tests it is still randomly accepted Providing the starting geology model can produce a close geophysical response to what was observed there is a well behaved convergence of the model response to the observed signal Figure 3 Pass Forward model and apply geophysical tests 12 Modifications rejected Pass revert to previous models Modifications accepted and saved
133. hysics with assistance from BRGM and Geoscience Australia In particular IG acknowledges the untiring efforts of Richard Lane from GA in following the path towards a volumetric stochastic approach to characterizing the 3D geological uncertainty 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 151 Conients Help Top References Contents Help Top 4 Back gt Aug C 2004 Mod lisation g ologique 3D et caract risation des incentitudes par la m thode du champ de potentiel PhD thesis to be defended in December 2004 Ecole des Mines de Paris Bosch M 1999 Lithologic tomography from plural geophysical data to lithology estimation J Geophys Res 104 749 766 Bosch M Guillen A and Ledru P 2001 Lithologic tomography an application to geophysical data from the Cadomian belt of northern Brittany France Tectonophysics 331 197 228 Bosch M and McGaughey J 2001 Joint inversion of gravity and magnetic data under lithologic constraints The Leading Edge 20 877 881 Bosch M Meza R Jimenez R and Honig C 2005 Geostatistical inversion of gravity and magnetic data in 3D Expanded Abstract SEG 75th Annual Exposition and Annual Meeting 6 11 November 2005 Houston Texas Bosch M Meza R Jimenez R and Honig A 2006 Joint gravity and magnetic inversion in 3D using Monte Carlo methods Geophysics 71 G153 G156
134. iates Pty Ltd 4 Back gt GeoModeller User Manual 126 Conients Help Top Contents Help Top q Back gt lt Run gt an alphanumeric string or identifier that identifies the Run to be executed e lt Testing gt an alphanumeric string or identifier that identifies this is a test run do not use turns on debug prints etc e lt MPI gt an alphanumeric string or identifier that identifies the Run may be ona cluster and that the load can be organised in a Master Slave fashion using the openMPI protocol lt CHECK gt an alphanumeric string or identifier that identifies the Run may also write checkpoint restart files for very large silumations that take a lot of resources and so are worth being able to break and start again from a known point lt Respone gt an alphanumeric string or identifier that identifies the response kernels for a spatial forward model from each of the litology units is to be saved For gravity this is one grid per unit for magnetics it the 3 component grids With these response kernels a property optimization can then be run An inversion Run may take 12 500 hours or more to reach completion The first task is to compute the initial model response for each of the requested geophysical data types for example Gravimetry Magnetism The geophysical unit response function stored as a kernel voxet is used to sum the geophysical responses at each g
135. ie 1 Modifie 2 Therm fa T HeatPr FB Tempe D BP vertica IY BB vertica D EE Horizot A dh a 3 Lithology Hide all views of this field Field Visualisation Manager Appearance Edit Colours and Clips Display color table Contouring Histogram Visual Filter Gutenberg Richter Plot Polynomial approximation Cross plot with 22 Multi crossplot with Multifield analysis x 2 Delete Properties Type Integer Alias lithology Approx Memory 117 07 Kb This can also be done using the New Case from Voxet task described later or simply directly in the main 3D Geomodeller tool Once these conditions are met you would Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 7 Contents Help Top lt 4 Back gt Taking care lauch the tool you want to use eg Forward Model Heat and then set lithology properties The simulation will then be possible and the results can also be shown and queried in the main tool There is a great deal of excitement created when you have realized a geologically sound and coherent model consistent with the sparse geological observations you might have However for the unwary geologist the further step of also making a close match to the observed potential field data can sometimes seem bewildering and unnecessary It is reeommened that be
136. ies of Geology Formations Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 63 Contents Help Top lt 4 Back gt Remanence requires additional parameters describing the remanent magnetisation vector direction Remanence Example ProbabilityDistributionFunction type LogNormal mean 0 4784 stddev 0 9568 percentage 100 inclination 68 5 declination 169 2 Physical Properties a Distribution of Values Any physical property for a formation is never uniform and never perfectly known 3D GeoModeller allows for this by defining physical property values in terms of A statistical law or distribution A mean value AND e A standard deviation For example the density of a formation can be described as having a normal distribution with a mean of 2 7 g em and a standard deviation of 0 05 g em The set of allowed statistical laws and their associated parameters is documented in the following sections Note that the associated parameters are dependent on the particular statistical law and also on the property being specified Physical Properties Mixed Lithologies It is not uncommon for some mapped or modeled geology formation to consist of a mixture of lithologies with the various component lithologies having distinctive physical property values Broken Hill Formation for example might be defined as bein
137. ight want the 3D GeoModeller response to be computed without the standard padding Figure 16 3D GeoModeller standard method of reducing the edge effects in geophysical computa tions is to expand the model by reflecting and rotating the modelled geology itself across the edges and corners of the model For a source model S at each depth slice the model has the form given by fliplr flipud S flipud S fliplr flipud S fliplr S S fliplr S fliplr flipud S flipud S fliplr flipud S where fliplr flipud S flipud fliplr S rot180 S e rot180 is rotate by 180 degrees e fliplr is flip a 2D matrix left right Note that the response calculation performed at any location is restricted to the contribution from voxels that are within a region with maximum horizontal extent equal to NX or NY voxels away in either direction where NX and NY are the original Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 55 Contents Help Top lt 4 Back gt voxet dimensions The response can thus be though of as the response for a moving window where the window being considered is equal in size to twice the size of the central model less one voxel This reduces the size of the response kernel that must be calculated for the Case and speeds up the response calculation that is performed at each iteration It is an approximation tha
138. ill the valleys with material having the Bouguer density the Bouguer slab See discussion at Gravity Dataset and Topography Considerations Why is there no Set command to specify the magnetic properties in the air The above topo magnetic properties susceptibility and remanence are set to 0 by default and there is no practical reason for those values to ever differ from 0 SetReferenceDensity Default 2 67 g cm All gravity responses are computed on the basis of a density contrast the contrast between the density of the geology formation and a specified Reference Density value This Reference Density value is set using the SetReferenceDensity command Default Reference Density is 2 67 g cm Typically the Reference Density should be set to that density value that was used in the Bouguer or full terrain correction of the observed gravity dataset This command updates the inversions xml file SetReferenceMagneticFieldMagnitude Default 50000 nT All magnetic responses are computed as north east and Z downwards vector magnetic components using the induced magnetization vector and the remanent magnetization vector for each voxel in the geology Voxet model Since the induced magnetization vector is the product of the voxel s susceptibility and the Earth s magnetic field in the Project area the Earth s field must be defined in terms of magnitude inclination SetReferenceMagneticFieldInclination Defau
139. ing geology formations extend into the sky The SetUseTopo command creates a new lithology coded as formation 0 in the region above the topography c but this new formation is assigned the default density value which is the Reference Density The SetAboveTopoDensity command must be used to assign some other density value such as 0 g cm for air to this above topography region d Note that the recommended elevation of geophysical response computation is at least one voxel width above the top of the uppermost voxel in the model to minimise artefacts due to the stepped topography representation in the Voxet geology model d Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 56 Contents Help Top lt 4 Back gt SetAboveTopoDensity The CaseControl SetAboveTopoDensity is used to assign the density property to the air region above the topography Normally a value of zero would apply this is the default Notes To take the model topography into account you must specifically declare that with the SetUseTopo command IncludeBorder Effect The default density of the above topo zone is the Reference Density value default 2 67 g cm This SetAboveTopoDensity command must be used if you want to use 0 density for air Why would you ever want a non zero density value in the air You may want to f
140. io and perform a new set of inversions Runs on that new Case invbatch batch lt taskfile task gt where lt taskfile task gt contains CaseControl required string filename optional string case optional SetLaw_GMT SetLaw optional SetReferenceMagneticField optional Magnitude optional Inclination optional Declination optional Date optional double mag_error optional inclination_error optional declination_error optional double SetReferenceDensity default 2 67 optional string SetReferenceLithology optional double SetAboveTopoDensity default 0 0 optional bool IncludeBorderEffect default true where lt ilename gt is the relative or absolute path of the XML project file for the 3D GeoModeller inversion Case e case is the name of the inversion Case IncludeBorderEffect lt false true gt Sets whether or not the padded data is included in the computations The default IncludeBorderEffect true means that the padded data is included in the computed forward response See IncludeBorderEffect SetAboveTopoDensity sets the density property for the above topo region The density of this region is often set to 0 for air appropriate when working with Free Air gravity data It is also common to set the density of the above topo region to the Bouguer density value which is appropriate for modelling fully terrain corrected Bouguer gravity data See SetAboveTopoDen
141. ired RunInterval_GMT RunInterval lt RunIntervalList gt optional string statistical_voxet lt OutputFilename gt if not supplied make a standard name up required int32 threshold_percentage lt Threshold gt optional string log 17 where lt CaseXML gt the relative or absolute path of the XML project file for the 3D GeoModeller inversion Case e lt RunIntervalList gt lt RunIntervalList 1 gt lt RunIntervalList N gt e lt Threshold gt species a percent probability value 0 to 100 and is used to generate a set of probabilities for each lithology where the probability is recorded only where probability exceeds this specified threshold and a Null is recorded if none of the lithology probabilities exceed the threshold lt OutputFilename gt the filename of the output voxet of lithology probabilities and optionally the relative or absolute path of the output directory which must exist and where lt RunIntervalList N gt lt Run gt lt StartIteration gt lt EndIteration gt where e lt Run gt an alpha numeric string or identifier that identifies the inversion Run e lt StartIteration gt is the Iteration number from which point the statistics of the changing lithologies of the Run will be compiled e lt EndlIteration gt is the Iteration number up to which point the statistics of the changing lithologies of the Run will be compiled The MakeSuperSummaryStats command is a key inversio
142. ity and magnetics might be in order Finally when you have worked hard on the model and the properties a full stochastic inversion of both properties and the geology model can still yield information about the unknowns that will help your interpretation With v2012 there are several paths you might take to specify rock properties in your model You may end up using a mixture of all methods It largely depends upon the availability of a statistical significant set of observed rock properties If you do not have much in the way of site specific rock property observations for a unit you will have to take the route of a best estimate of the population based upon limited testing Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 92 Contents Help Top lt 4 Back gt and a literature review This is the first method describe below The second method involves the use of classical and some innovative geostatistical analysis of your rock properties First approach Whole of Population Estimate You are required to specify a Law such as Gaussian or Normal To do this requires a mean and standard deviation When you have access to the near surface rocks you have some chance of doing this For deeper rocks there is a lot of uncertainty The need for a property distribution law comes from the full inversion scenario When you are performing a forward model just the mea
143. ity function is OO D The expected value is x F 1 1 k where FO is the gamma function If we use x 1 for Commonality the Weibull distribution reduces to an exponential type PDF whilst if we use K 2 the Weibull distribution reduces to an Rayleigh type PDF Figure 20 100 00 10 00 1 00 Commonality misfit value 0 10 100 80 60 40 20 0 Same as the reference model Graph showing the relationship between Same and Commonality Misfit Figure 21 2 0 Exponential Weibull 0O 5 1 0 Rayleigh Weibull 0 5 2 0 1 5 Li a 1 0 05 0 0 05 1 0 E 2 0 Commonal ity misfit value Plots of Commonality Misfit and the probability distribution function PDF for two different Weibull specifications Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 70 Contents Help Top lt 4 Back gt SetLaw Figure 22 2 0 J Exponential Weibull 0 5 1 0 Rayleigh Weibull 0 5 2 0 PDF J 100 80 60 40 20 Same as the reference model Plots of Same and the probability distribution function PDF for the same two Weibull specifications given in Figure 21 Use of x 1 is akin to saying that the reference model is the best estimate of the geology and this should be the most likely arrangement presented for evaluation with respect to the potential field data is an expres
144. jpg image files which are then collated into a movie in AVI format avi The movie can be played on a range of Windows movie players such as Windows Media Player or QuickTime produce a movie of the evolution of the inversion of a field on a section output to JPEG ERS message MakeEvolutionMovie_GMT required string filename lt CaseXML gt optional string case 2 required RunInterval_GMT RunInterval lt RunIntervalList gt just one interval is supported here optional int32 MaxPixelCols lt MaxCols gt default 500 optional int32 MaxPixelRows lt MaxRows gt default 500 optional double VerticalExaggeration lt VerticalExaggeration gt default 1 0 optional int32 QualityPercentage lt QualityPercentage gt default 100 optional int32 FramesPerSecond lt FramesPerSecond gt default 100 optional int32 IterationIncrement lt IterationIncrement gt default 2000 optional ColourScheme lut lt ColourScheme gt default Colours optional ScaleOption_GMT Scaling lt ScaleOption gt optional EvolutionField show lt EvolutionField gt default Geology required string Section lt Section gt optional string movie lt OutputFilename gt default puts movie in the Case run with name made from section vertExag EvolutionField where lt CaseXML gt the relative or absolute path of the XML project file for the 3D GeoModeller inversion Case lt MaxCols gt the maximum number of pi
145. ke all Geoscience Data Consistent 3D geology model built using all available geological information This is meant to be a close model to the truth The basic 3D GeoModeller technology deals with geological observations and approaches to build the model These geological observations are realized in a consistent 3D sense via the rules The rules resolve a smoothed best fit geology of all the observations The technology used always delivers a result and as a geoscientist your job is to vet these models to drive them to a result you find convincing By this is meant a condition where all the facts and interpretative aspects provide you with your best reference model The following diagram shows the range of possible geological inputs you have at your disposal to achieve this state 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 13 Contents Help Top lt 4 Back gt Figure 1 Faults Faulk boundary points Faull oneniaton panis Fault 1 Zero deglacement boundary on faut surlace Constraining formations Fauitfault relationships Model outputs 7 Faul series relationships Boundary points ae Representa of the mode from other Onentaton peins Vowel array Basic mapping aj l moder rat ya surface a Axial guias R GeoModeller information outline hd aia Anal surfane onientabon pants 3D GeoModeller Information model Contents Help Top
146. kes sense with as little trouble as possible Some of the innovation in v2012 revolves around accessing clusters grids of computers and the cloud The comment is sometimes made that it is lack of computing power that often restricts the size and detail of geoscientific investigations not the lack of high quality geophysical data Intrepid BRGM are committed to providing access to complex algorithms that work on large datasets with a minimum of fuss The style of documenting follows the language definition and task nature with inserts from the Wizard pages to show the tie ins NewRun RUN The NewRun command sets up a new inversion Run This would typically be one of several such Runs which might be executed for a given Case NewRun lt Run gt lt ArgList gt where lt CaseXML gt the relative or absolute path of the XML project file for the 3D GeoModeller inversion Case including the xml extension Note that a Case is a copy of an original 3D GeoModeller project this parameter points to the xml file of the copy lt Run gt an alphanumeric string or identifier that will uniquely identify this run The characters must be valid characters for file naming purposes but excluding the space character e lt ArgList gt lt Number of Iterations gt the total number of inversion iterations that will be performed in this inversion run The NewRun does not perform an inversion operation but simply
147. king VerticalExaggeration into account The resultant image will have a horizontal pixel dimension equal to MaxCols and the vertical pixel dimension will be determined according to the Section s aspect ratio and the VerticalExaggeration factor For example InversionTask MakeSectionImage filename InputGeology slab_vertical_20070420c slab_vertical_20070420c xml run Run_1 case Case_1 get_function existing voxet SuperSummaryStats_iterations_100000_70000_85_super vo statistical_field MostProbableThresholded transform GetField threshold 90 Section 500_mN MaxPixelCols 1000 MaxPixelRows 500 VerticalExaggeration 1 0 QualityPercentage 95 lut LithologyColours Scaling doLog false image Run_1_SSSVoxet85_500_mN_MostProbableThresholded_85_LithologyColours jpg MakeSectionMovie The MakeSectionMovie command produces a movie that shows a Section which sweeps across the 3D geology model showing a sequence of Section images of geology or some physical property parameter Status not shipping in v2012 Each of the movie frames is a discrete Section orthogonal to the line of sweep showing an image of the lithology or other property on that Section A set of these Sections are generated at small user specified intervals along the line of sweep The collation of these Section images movie frames into a movie achieves the effect of a Section sweeping acr
148. l in the 3D GeoModeller Project MeshGrid is any 2D or 3D regular irregular grid or surface With the new version of Geomodeller the underlying systems libraries from Intrepid now include a fully systematic way to store these MeshGrids in a binary form together with all the extended metadata Any data type eg Integer Float Date Boolean Vector Partial support for Tensor grids is also present Unlike the line or profile ways to gather and store most original observations of geophysics this variant concentrates on random point data and grids However full geophysical databases can now be introduced into Geomodeller as these MeshGrids of random point observations Kriging can then be used to produce grids Voxet is a special case of MeshGrid and in particular the 3D lithology model can be stored as an integer geology voxet There may be several different Voxets in a Case The Case Voxet is the voxel lithology model derived from the 3D GeoModeller Project when a Case is created A Run has an Initial Voxet typically derived from the Case Voxet and a Final Voxet being the final geology model of some inversion Run which might then be used as the start of another Run The full 3D voxel geology model at any given iteration in a Run can also be generated again as a Voxet The Reference Voxet used as the reference geology model against which the current model might be tested during a Run is also a Voxet It is often the same
149. l 111 Contents Help Top lt 4 Back gt Initialize Style Commands One of the prerequisites for a 3D GeoModeller inversion Run is a voxet a 3D voxel model of the geology and also voxets defining the 3D distribution of associated physical properties such as density magnetization and remanence The various InitialiseStyle commands give the user a flexible set of commands for defining exactly the initial state to be used for an inversion Run These range from simply specifying the file name for the voxet that contains the required initial state through to commands that perform the initialization assigning properties values to voxels in accordance with specified parameter settings PropertyLithologylnitialiseStyle The typical initial lithology for an inversion Run will be that derived from a 3D GeoModeller geology model default There are however alternative lithology starting points that you might want to define You might want to continue an inversion from some previous inversion run for example Or your starting model may be one that is independent from 3D GeoModeller For example it could be a voxel file created via some third party software source The LithologyInitialiseStyle command initializes the distribution of lithologies to be used for an inversion Run The default will be the voxet generated when a Case is initialised but you can specify any valid voxel file enum PropertyInitialiseStyle From
150. l resides in the Gzz component for inversion so use the complete tensor if available Much of the detail shape information from the geology bodies that are causing the anomalies in the first place lies within the curvature as captured by the full tensor Intrepid supports tensor grids so that all the signal is in one place properly registered and also properly processed With the new 64 bit memory computers now generally available the ability to handle this signal type is not limited by speed or memory constraints The amplitude of the tensor signal is separated from the orientation of the tensor The amplitudes or Eigenvalues are invariant to the coordinate system In the context of inversion the local rotations of the signal may be less important than the signal amplitude as a driver for making the inversion converge The number of terms of concern changes from five to two and so is very significant computationally Of course the occasional iteration can be scheduled to look at the rotations as well as the amplitudes This is a proposed optimization step for full tensor gradient inversions for future release Also part of this mix is the horizontal gradient tensor as measured by the Fugro Falcon system It warrents special consideration as it too has more integrity than just treating a component of the curvature gradient as the signal there is extra embedded phase information in the signal During 2011 a workflow to process Falcon 2013 B
151. lement on the leading diagonal would cause any proposal to be rejected that included more than one voxel for the relevant formation in the vertical column of the lithological model that is the host to the voxel being examined With a setting of true on the leading diagonal the source and target formations are the same and we have thus we have specified that this formation cannot occur above itself This can only be satisfied if there is at most one occurrence of this formation in the vertical column of the mesh that hosts the new proposal Values of true for a pair of positions that are symmetrical about the leading diagonal i e the diagonal from top left to bottom right would be saying that Formation A cannot occur above Formation B and Formation B cannot occur above Formation A This instructs the program that a proposal will only be accepted if at most a single occurrence of either Formation A or Formation B is present in the vertical column of the mesh that hosts the new proposal Values of false for a pair of positions that are symmetrical about the leading diagonal is simply instructing the program that we have no preference for the vertical order of the pair of formations We will accept proposals with Formation A above Formation B and we will also accept proposals with Formation B above Formation A Implementation A primitive function exists to apply the PreserveVerticalRelationship test to a single voxel as would be required for te
152. ler User Manual 131 Contents Help Top lt 4 Back gt Contents Help Top e lt StartIteration gt the Iteration number from which point the IterationIncrement counter will start and snapshots of the Section lithology will be generated for every IterationIncrement thereafter until e lt EndlIteration gt the Iteration number at which point the process is to be stopped e lt ScaleOption gt lt LinearOrLog gt lt minClip gt lt maxClip gt where e lt LinearOrLog gt 0 for Linear and 1 for Log lt minClip gt minimum value or use Auto to have the software automatically calculate this lt maxClip gt maximum value or use Auto to have the software automatically calculate this The movies produced by the MakeEvolutionMovie command provide one means of reviewing or analyzing millions of discrete geology models Of course even these movies are only showing a subset of the geology of those millions of models They show geology for a single Section through the 3D model They show the geology of that Section for a subset of models one in every IterationIncrement Nevertheless the movies do provide a useful rapid review of many models which can be used to Review the behaviour of the inversion One would be looking to see evidence that the evolving geology cross section continues to look like a realistic geology section If the component bodies of geology shown on
153. lity 0 0000001 Slab remanence 0 05 0 00000 100 25 115 only for the remanence case e Host remanence 0 00 0 00000 100 0 00 The following scenarios are to be replicated to gain a full or better understading of what is possible e Forward Model Propose a start model compute gravity response e Prior Only Propose a geological model explore probability space implied by the geological constraints Fixed Geometry Solve for properties using a bounded least squares fit BiModal Property Only No proposed body just a proposed density contrast Constrained Geology Use gravity to constrain result e Constrained Geology Use magnetics assuming induced response only Constrained Geology Joint gravity and magnetics Constrained Geology Use magnetics with the possibility of remanence Constrained Geology Use observed tensor gradients Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 158 Conients Help Top 4 Back gt Figure 29 Layout of 8d simple slab model Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 159 Contents Help Top lt 4 Back gt Appendix 5 Report File Example Every batch inversion run also produces an asoociated report file that you should examine to verify that what occurred in the run is as you expected Here is a sample repo
154. lking 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual Conients Help Top Detail Logic Flow Charts Contents Help Top At the local level two possible courses of action are chosen on a 50 50 basis As above at a frontier you can modify a boundary See Figure 17 Also you can choose to change the physical properties See Figure 18 Figure 23 Current Models YES Boundary Modification YES Apply Homogenous Filter Select Voxel at Morphological random Filter Open Close Test and apply Test and apply proposal s proposal eS 4 Apply Erosion Dilation Filter Morphological Filter NO Erosion Dilation Test and apply _____ proposal s Neither morphological filter applied NO Single Voxel Boundary Filter Test and apply proposal y Inversion Iteration Scheme the case where you might want to change a boundary 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd GeoModeller User Manual Conients Help Top Figure 24 Geology Tests Examples i Are set Commonality tests satisfied ii Are set Volume Ratio amp or Shape Ratio tests satisfied CURRENT ee Form next proposal a Decide whether changing property only or lithology amp property
155. logy models for which the geophysical misfits between observed field and model computed are small The misfits may not be small at the start of an inversion Run but will typically have reduced to an acceptably low level of misfit after some initial burn in period To examine the misfits plot the misfit data using Excel or a similar graphing software Then specify an appropriate StartIteration value which excludes those initial lithology models from the statistics compilation PROTOBUF EXAMPLE rSummaryStats filename InputGeology CF83 CF83 xml1 statistical_voxet InputGeology CF83 R1 super_stats vo Runinterval run R1 case C5 start_iterations 10000000 end_iterations 20000000 threshold_percentage 90 Contents Help Top And by way of example of outputs from this command the following are 2 possible voxel output files derived from inverting using a standard vertical component of gravity dataset We have 2 queries one at 85 probability and the other at 95 The names of the various properties are defined in the voxet header 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 135 Conients Help Top 4 Back gt For ModelFromCase_Gravity_done they are in SuperSummaryStats_Case_4_Run_1_iterations_3000000_1000000_85_super vo AND identically also in SuperSummaryStats_Case_4_Run_1_iterations_3000000_1000000_95_super vo Property 1
156. lt 90 degrees and declination SetReferenceMagneticFieldDeclination Default 0 degrees This command updates the inversions xml file There is an IGRF calculator in 3D GeoModeller physical properties dialog box which can be used to calculate the magnitude inclination and declination values See also the discussion at Magnetic Considerations regarding the use of a reduced to pole RTP field magnetic dataset SetReferenceMagneticFieldinclination Default 90 degrees See comment in SetReferenceMagneticFieldMagnitude Default 50000 nT Magnetic field inclination is positive in the northern magnetic hemisphere and negative in the southern hemisphere When using and RTP field magnetic dataset the inclination should be set to 90 but see the discussion at Magnetic Considerations This command updates the inversions xml file Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 57 Contents Help Top lt 4 Back gt SetReferenceMagneticFieldDeclination Default 0 degrees See comment inSetReferenceMagneticFieldMagnitude Default 50000 nT This command updates the inversions xml file Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 58 Contents Help Top lt 4 Back gt SetReferenceLithology Default the Case Voxet The SetReferenceLithology command is use
157. mits of the Voxet voxel geology model are derived from the geophysical grids The geophysical grids may be larger than the 3D GeoModeller Project only those grid cells that overlap within the Project are used The geophysical grids may be smaller than the 3D GeoModeller Project A Voxet for the restricted horizontal extent will be generated The geophysical grids may have null data cells Such cells are simply ignored no computation of model response is performed for those cell locations Grid Datum and Projection The user must ensure that the datum and projection of grids datasets is the same as that used for the geology model 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 48 Conients Help Top Contents Help Top lt 4 Back gt Figure 14 Recommended practice for modelling when using Free Air gravity data Simple Bouguer and fully terrain corrected Complete Bouguer gravity is a gravity dataset for which the Free Air correction has been applied and the effects due to topography hills of mass above the observation and valleys of air below the observation have been corrected for to different degrees Since the observed data no longer contain the effect of the Earth Air boundary the corresponding computed model data must reproduce that by replacing the Air with material having the same density as was used for the Bouguer correction that was applied
158. mond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 147 Contents Help Top lt 4 Back gt Predefined Structural Elements There are a series of predefined structural elements some of which are used as the default operators for 3D GeoModeller morphological filter operations Here is a list of predefined structural elements used in the morphological filters Structural Element Name CUBE_3x3_FACE CUBE_3x3_FACE_EDGE CUBE_3x3_FACE_EDGE_VERTEX CUBE_3x3_SOUTH CUBE_3x3_NORTH CUBE_3x3_WEST CUBE_3x3_EAST CUBE_3x3_TOP CUBE_3x3_BOTTOM CUBE_5x5_TRICROSS CUBE_5x5_FACE_EDGE_VERTEX If you want to use a Morphological Filter for your inversion the following provides an example Dilation and Erosion Morphological Filters As noted above the Dilation Or Erosion Filter is not so much a filter but rather is specifically a method for proposing a global migration of a geology boundary by approximately one voxel in some randomly chosen direction By default the DilationOrErosionFilter is on The details of the default behavior of this morphological filter are as follows After a every 5000 iterations e Randomly select a geological unit e Randomly select a process either growing a boundary dilation or thinning it erosion e Randomly select a structural element from the following set of six predefined structural elements CUBE_3x3_SOUTH CUBE_3x3_NORTH CUBE_3x3_WEST CUBE_38x3_EAST CUBE_38x3_TOP and
159. n and is the Gdd component of the gravity gradient tensor 3D GeoModeller forward and inverse geophysics computation can directly compute the Gdd component see Geophysical Dataset Types Units and Grid File Formats Grids 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 49 Contents Help Top lt 4 Back gt Contents Help Top If using a Gdd dataset derived by 1VD filtering of a gravity dataset the filtered 1VD dataset might typically have units of milligals metre whereas 3D GeoModeller requires Gdd in units of Eotvos to convert from milligals metre to Eotvos multiply by 10 000 see Appendix 1 Units and Units Conversions Figure 15 Recommended practice for modelling when using fully terrain corrected Bouguer grav ity data Magnetic Considerations In addition to the many general considerations for all types of geophysical grids Gravity Dataset and Topography Considerations above for magnetic data the following details must be specified and various considerations taken into account The field strength inclination and declination of the Earth s magnetic field must be specified These can either be predefined in the 3D GeoModeller Project or can be set later by using CaseControl commands Appropriate values can be derived from the International Magnetic Reference Field IGRF an IGRF calculator is included in 3D GeoModeller physical properties dialog The
160. n results reporting tool The lithology probability data recorded in the SuperSummaryStats voxet are then used by a range of other commands which generate various derived products such as Section images showing most probable lithology The SuperSummaryStats voxet contains the following fields ChangeCount which is defined as the total number of accepted proposals for each location A proposal is counted regardless of whether it was an IntraProposal or InterProposal and regardless of whether the InterProposal involves a change to Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid lt 4 Back gt GeoModeller User Manual 134 Conients Help Top InversionTask MakeSupe lt 4 Back gt the formation or not MeanDensity StdDevDensity for example depending on the geophysics datasets inverted e MostProbable MostProbableThresholded probabilities gt specified Threshold ProbabilityO Probability1 Probability2 where 0 is the AboveTopo region and 1 2 are indexes to the lithologies of the model and are defined in the Case inversions xml file The MakeSuperSummaryStats command can be used to collate results from several inversion Runs For each Run the sub set range of lithology models to be used in the statistics compilation can be specified in terms of a range of iteration numbers from the inversion Run Typically you will choose to use only those litho
161. n values are used Second approach Geostatistical Analysis then Estimation In this case the recommended way to create a 3D property model for one or more of your rock units is to use the domain kriging feature You may have a statistically significant number of boreholes that are logged for each of the physical properties you wish to estimate The mechanism to get an optimum property model constrained by a proper geostatistical analysis of your data involves the following steps Import the borehole Transfer the XYZ and property data to a 3D observed points MeshGrid e Prior to this you create a 3D geology model of the geology using the standard 3D geology modelling techniques Create one or more variograms of your property constrained by each geology unit This is known as domain kriging Your seperation distances between samples is calculated following the trends of the geology model implicit model potentials Interpolate the property for each unit that you have observations This results in a new MeshGrid that is a regular 3D voxet Transfer the 3D geology model into this new voxet For any unit you do not have sampled property data just use the first proceedure Forward models of gravity magnetics heat simulation response all follow this path While v2012 does support tetrahedron meshes the main way to use these techniques is still via the regular 3D voxet approach It is expected that all of this fu
162. nDensity Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 137 Contents Help Top lt 4 Back gt StdDevDensity Probablity0 Probablity1 e lt Section gt is the name of an existing Section in the 3D GeoModeller Project lt MaxCols gt the maximum number of pixels across the JPEG image of the Section lt MaxRows gt the maximum number of pixels down the JPEG image of the Section see further note e lt VerticalExaggeration gt typically 1 is the Section Vertical Exaggeration to be used see further note below lt QualityPercentage gt say 80 to 100 defines the quality of the JPEG snapshots images 100 uses no JPEG compression lt ColourScheme gt is one of lt LithologyColours Colours Greyscale gt lt ScaleOption gt lt LinearOrLog gt lt minClip gt lt maxClip gt where e lt LinearOrLog gt 0 for Linear and 1 for Log lt minClip gt minimum value or use Auto to have the software automatically calculate this lt maxClip gt maximum value or use Auto to have the software automatically calculate this e lt OutputFile gt the output filename jpg The Section must exist in the 3D GeoModeller Project The command line provides only a Section name the further necessary information about where is that Section in 3D space is determined from the 3D GeoModeller Project
163. nceCount 0 InterAcceptanceCount 0 ShapeTestCount 0 AcceptanceCount 0 VolumeRejectCount 0 CommonalityVolumeRejectCount 0 CommonalityRejectCount 0 CommonalityVolumeTestCount 0 Counter 0 RunFieldResult Type String RejectCount 0 TestCount 0 TrendGrid Type String Path String ObservedGrid Type String RemoveRegional true Precision 3 1415926535897932384626433832795 RelativeElevation 3 1415926535897932384626433832795 RemoveRegionalDegree 0 Sampling 0 GridPath String RemoveRegionalRate 0 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 157 Contents Help Top lt 4 Back gt Appendix 4 Simple Slab Example Prior to undertaking a full scale inversion exercise using the technology described in this manual it is recommended that you review and prove to yourself you understand and can reproduce each of the following scenarios on a simple slab model 3D GeoModeller inversion testing with its many options can be easily demonstrated using this simple slab example The strategy being employed is to propose a vertical body with dimensions that roughly match what can bee seen in the gravitational amp magnetic response We propose a simple vertical slab as a starting model with the following SI units and properties e Buried 100 m Dimension of 100 x 200 x 400m The Slab density 3 67 g cm Host density 2 67 g cm Slab susceptibility 0 005 e Host susceptibi
164. nctionality described above will also work for irregular grids and meshes in the not too distant future Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 93 Conients Help Top q Back gt Property Optimization We provide a technology algorithm that can give you a bounded least squares optimization of the property estimates using your model with relative coarse cells in the XY and finer ones in the Z direction To make sure you use representative values of observed data a maxAbsoluteObserved field is available to ignore outliers The solver uses a weighted least squares approach over the whole 3D assembly of cells and properties to best fit the observed data and the response from each individual unit summed by its response kernels This is a very important way point in the process of integrating geology and geophysics in 3D Currently at 3D GeoModeller v2012 this is a batch only function via the invbatch tool When you have both magnetic and gravity properties to consider it advisable to do each seperately If both are specified via the Observed Grids just the magnetics case will be calculated The formal lexicon for this task Property optimization deterministic method to estimate best fit litho properties needs unit response for each lithology with at least 3 differing units a set of lithologies properties including Lower and Up
165. nd any error can be resolved by examining the underlying language lexicon For more examples of task files see the tutorial directories on the distribution area PROTOBUF EXAMPLE inputvoxet testArea_2suites vo case Case_1 new_project testArea_2suites_imported testArea_2suites_imported xml product Temperature formation index 1 field aboveC map interger number inside voxet to formation name formation index 2 field ZtoC formation index field basement formation index field BLS formation index field granites1 OPWNHE filename testArea_2suites_imported testArea_2suites_imported xml1 case Case_1 input_voxet testArea_2suites vo field_alias alias Lithology field Lithology SetLaw LithologyProperty lithology aboveC property ThermalConductivity ProbabilityDistributionFunction type Normal mean 2 0 stddev 0 2 LithologyProperty lithology ZtoC property ThermalConductivity ProbabilityDistributionFunction type Normal mean 1 4 stddev 0 2 LithologyProperty lithology basement property ThermalConductivity ProbabilityDistributionFunction type Normal mean 2 4 stddev 0 0 LithologyProperty lithology BLS property ThermalConductivity ProbabilityDistributionFunction type Normal mean 3 1 stddev 0 0 LithologyProperty lithol
166. netisation vector being 68 5 degrees downwards from horizontal and declination 169 2 degrees east of north 190 8 degrees east of north Units for Remanence Enter remanence as a magnetisation vector with the magnetisation strength in units of A m Some sources express the amplitude of remanence in terms of the K nigsberger ratio Qp see Appendix 1 Units and Units Conversions Units and Units Conversions for conversion to A m SetLaw Type 2 Inversion Control Properties of Geology Formations The CaseControl SetLaw command is also used to set inversion control properties of geology formations These additional properties of the geology formations are used to control or limit the changes to geology formation boundaries that can be proposed during the inversion iterations There are six inversion control properties that can be set Movable Index Commonality CommonalityVolume ShapeRatio and VolumeRatio For Properties Moveable amp Fixed Controls if the unit can be allowed to move If you wish to constrain some of the upper units and mostly look at basement this can be a useful mechanism e Example SetLaw LithologyProperty lithology Air property Movable fixed true LithologyProperty lithology Water property Movable fixed true LithologyProperty lithology SedUpper property Movable fixed true LithologyProperty lithology SedMiddle property Movable fixed true Litholog
167. oc 44 335 341 Mosegaard K and Tarantola A 1995 Monte Carlo sampling of solutions to inverse problems J Geophys Res 100 No B7 12431 12447 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 152 Contents Help Top lt 4 Back gt Sparse Data Only GeoModeller can create workable models with sparse data Geologically consistant 3D models can be built with surprisingly little data mode and late stage warping of the Plattengneis Shear Zone in tho Eastorn Alps Tectonophysics 412 2008 87 104 PAIN AR ERED Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 153 Conients Help Top Appendix 1 Contents Help Top 4 Back gt Units and Units Conversions 3D GeoModeller supports projected spatial coordinates for its project box You specify an XY datum and projection as well as a height datum The Z dimension can be in units of length or time However once potential field forward or inverse modeling is required the Z unit should be metres In general it is recommended that SI units be used throughout your study Comment on UNITS for the geophysical datasets Magnetism nT MagGradients nT m Gravity use milligals ie mGal which are 10 m s Gravity Gradients We use Eotvos which are 10 s If computing from milligals to milligals metre these units are 10
168. ociates Pty Ltd 4 Back gt GeoModeller User Manual 154 Conients Help Top Appendix 2 4 Back gt Programmer notes on voxel coordinates and indices The following explains the conventions on how binary or ASCII data is packed into a voxet The position of the voxel index 1 1 1 in the modifications file corresponds to the bottom south west corner In InvGravMag_CurrrentModel the voxel indices i j k are given by i Standard_Integer 1 x a GetPasX j Standard_Integer 1 y b GetPasY k Standard_Integer 1 z c GetPasZ0 In dfaDefs_VoxetCS the voxel indices ix iy iz are given by iy Xmin dx 1 iy O Ymin f dy 1 Z Znin IZ dz 1 and the geographic locations of the voxel centres x y z are given by X Xmin dx x ix 1 Y Ymin t Y X71 dz x iz 1 Z Zmin In ModelAPI_VoxelModel which writes the initial voxel file the geographic locations of the voxel centres x y z are given by Standard_Real x TheOrigin X i x TheXSize TheXSize 2 Standard_Real y TheOrigin Y j x TheYSize TheYSize 2 Standard_Real z TheOrigin ZQ k x TheZSize TheZSize 2 where i 0 ny_1 j 0 ny_ and k 0 n _ Appendix 3 Sample of Populated Inversion Case XML file generated directly from the schema Contents Help Top All parameters including many optional ones are present The values are dummy and are automatically placed there
169. odelling and then the extra options and settings are presented following the case run execute flow Each page in the wizard corresponds to the important parameters to be set Page 1 choose Case Run Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 28 Contents Help Top lt 4 Back gt Page 2 choose observed grids and properties and response to calculate eg Gravity Page 3 set the main case control parameters Page 4 set the main run control parameters Page 5 set the overall controls number of iterations Page 6 final decisons about the Batch Interactive Cloud and submit If running interactively a progress misfit is shown When finished a prompt for 3P Summary Statistics from Inversion R x Case1 v Runi X 5 0 45 40 35 g 3 0 25 2 0 15 1 0 05 10 000 20 000 30 000 40 000 50 000 60 000 70 000 80 000 90 000 100 00 Iterations From 40000 To 100000 Threshold 90 va OK EJ close generating a Statisical analysis is given A simple check that the requested property distributions have been honoured while performing the inversion can be made by examining the individual finishing position property histogram for each lithology unit against what was requested at the start Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt
170. oftware automatically calculate this lt OutputReport gt the filename of the output xxx histogram report file and optionally the relative or absolute path of the output directory which must exist The MakeHistogram command is not suitable for reporting information from a SuperSummaryStats voxet which contains statistical information about many models rather than actual data values of an actual model The MakeHistogram command can be applied to 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 143 Conients Help Top RunState lt 4 Back gt The Case voxet The initial and final voxets of an inversion Run Any specifically derived geology voxet derived at some iteration point of an inversion Run For example InversionTask MakeHistogram filename InputGeology slab_vertical_20070420c slab_vertical_20070420c xml run Run_1 case Case_1 voxet 70000 vo lithology_field Lithology property_field Density number_of_bins 51 Scaling doLog false report Histogram_Density_70000 rpt The RunState command is a task that regenerates the Geology Model Voxet that existed at a specified iteration of a nominated inversion Run literally the process recreates the state of the Run at that point The process uses the Run s initial vo Geology Model Voxet and the set of changes recorded in the Run s mo
171. ogy granites1 property ThermalConductivity ProbabilityDistributionFunction type Normal mean 3 1 stddev 0 0 LithologyProperty lithology aboveC property HeatProductionRate Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 86 Contents Help Top lt 4 Back gt ProbabilityDistributionFunction type Normal mean 0 000001 stddev 0 0 LithologyProperty lithology ZtoC property HeatProductionRate ProbabilityDistributionFunction type Normal mean 0 000001 stddev 0 0 LithologyProperty lithology basement property HeatProductionRate ProbabilityDistributionFunction type Normal mean 0 000002 stddev 0 0 LithologyProperty lithology BLS property HeatProductionRate ProbabilityDistributionFunction type Normal mean 0 000011 stddev 0 0000015 LithologyProperty lithology granites1 property HeatProductionRate ProbabilityDistributionFunction type Normal mean 0 000008 stddev 0 0000035 Advanced true Surface_Temperature_Law type Log_normal mean 22 stddev 0 percentage 100 Base_Heatflow_Law type Log_normal mean 0 036 stddev 0 percentage 100 MaxResidualTemperature 0 0001 NumberOfIterations 10000 Parameter Sweep Heat resource uncertainty studies Also in batch an heat resource uncertainty estimati
172. ols 900 MaxPixelRows 900 VerticalExaggeration 3 FramesPerSecond 6 QualityPercentage 100 lut LithologyColours Scaling doLog false linear Section 302 17 movie Results EvolutionMovie_C5_R1_ Lithology_302 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 133 Contents Help Top lt 4 Back gt MakeSuperSummaryStats The primary way of querying outputs from an inversion run is via inversion statistics These are captured in an output voxel with 10 or more fields The name of the report voxel also carries the statistical probability for example 80 The MakeSuperSummaryStats command analyses the data for a user selected range of inversion lithology models derived from one or more inversion Runs and collates these as a set of probabilities the probability of each lithology in each of the voxels of the voxel model This set of probabilities is recorded in a voxet file format make a comprehensive set of stats for the current job use predefined field names for the output fields place in a special stats voxet for later interogation plotting etc rule to construct the default name OutPrefix dfastr printf s s s SuperSummaryStatstats_iterations_ d_ d_ d parent_dir case run to from threshold_ percentage message MakeSuperSummaryStats_GMT required string filename lt CaseXML gt optional string case 2 requ
173. om the 6 face neighbors of the voxel for which a change of formation is proposed taking into account whether the proposed change in formation will produce a decrease in the Same value for the old lithology an increase in the Same value for the new formation or no change to the Same values localAbundance gives rise to prob_Back values equal to the number of voxels in the face neighborhood equal to the old lithology divided by 6 and prob_Forward values equal to the number of voxels in the face neighborhood equal to the new lithology divided by 6 for example CommonalityTest SetWeights none AllowCommonalityVolumeTest In batch the CommonalityVolume is a geology test that can be applied during the Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 115 Conients Help Top lt 4 Back gt inversion to jointly control the number of voxels assigned to each formation and the number of voxels that this formation has in common with the distribution for this formation in the reference model You can set different weightings to control the way in which the CommonalityVolume test is applied message Commonality VolumeTest_GMT enum Commonality VolumeWeightType none 0 LocalAbundance 1 required Commonality VolumeWeightType SetWeights 1 default LocalAbundance optional bool Allow 2 default tr
174. on so it is expected that you have reviewed and created at least one model see the Tutorials A H You can then choose to do 3D forward geophysics modelling The first page of the wizard is shown below It is gravity and magnetics specific The convention used to measure and store the vector and tensor gradient field components is also reported Intrepid has a formal way to capture and record this in all tools You access this via Geophysics gt 3D gt ForwardModel Source Select the components to calculate during forward modeling Project Name ersion InputGeology slab_vertical_20070420c slab_vertical_20070420c xml B se New case name Case1 Create a new case Clone an existing case Case_1 Fields to compute ujcz Vertical Gravity Gravity Tensors Acx Gxy Gxz lGyy Gyz Ezz Em Total Magnetic Intensity Magnetic Tensors Em Coordinate system END x y z Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 22 Contents Help Top lt 4 Back gt Forward Model Parameters Page The second page shows the promts for optional observation grids Any common geophysical grid format is supported eg ERMapper Geosoft etc The data in the grid must contain values that are a true measure of the field you wish to compare with your model An image tiff jpeg does not really contain data Importantly at v2012 the technology no
175. ons on a regional scale can be estimated A parameter sweep automatically creates many connected scenarios each of which is run on one or many computers in a cluster The method takes the above task and adds a wrapper to create many instances and then manages running these simulations All elements of the simulation can be perturbed so that typically either boundary conditions or physical properties such as heat production rate for the important units are cycled through 2 or 3 states making a combination of simulations that constitutes a stochastic study of the uncertainties For instance with 5 variables such as a unit s Heat Production Rate Base Boundary heat flow each with 2 states gives 32 cases and with 8 states gives 243 cases A final pass gathers all the results and produces statistical population in a voxet with the heat flow and temperature variability for each cell PROTOBUF EXAMPLE InversionTask CreateCaseFromLithologyVoxet inputvoxet testArea_2suites_sub2 vo case Case_1 author des new_project testArea_2suites_imported testArea_2suites_imported xml product Temperature formation index 1 field aboveC map interger number inside voxet to formation name formation index 2 field ZtoC formation index field basement formation index field BLS BWNHE 7 Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associa
176. onse grid files and optionally the relative or absolute path of the output directory The full output filename uses the supplied prefix together with a Keyword designating the geophysical data type for example Gravimetry Magnetism Gdd The Z elevation of voxel centroids will range from ElevationMaxVoxet nZ x zCellSize zCellSize 2 to ElevationMaxVoxet zCellSize 2 where nZ Number of horizontal sheets of voxels in the geology Voxet such that ElevationMaxVoxet nZ x zCellSize lt ElevationMinVoxet and ElevationMaxVoxet nZ 1 x zCellSize lt ElevationMinVoxet Thus the Z division of the 3D GeoModeller Project into voxels is calculated from the specified top ElevationMaxVoxet then working downwards until the lower limit is reached That lower limit does not need to be specified exactly The easting will range from EastMIN_VOXET The western edge of the most western voxels to EastMIN_VOXET NEAST x eCELLSIZE The eastern edge of the most eastern voxels where NEAST Number of voxels in the easting direction such that EastMIN_VOXET NEAST 1 x eCELLSIZE lt EastMAX_VOXET and EastMIN_VOXET NEAST x eCELLSIZE gt EastMAX_VOXET The northing will range from NorthMIN_VOXET The southern edge of the most western voxels to NorthMIN_VOXET NNORTH x nCELLSIZE The northern edge of the most northern voxels where NNORTH Number of voxels in the north direction such that NorthMIN_VOXET NNORTH 1 x nCELLSIZE lt NorthMAX_VOXET and Nor
177. onversion to a good fit can be achieved automatically but you will be left with a fragmented predicted geology that bears little relation to your staring model Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 38 Conients Help Top 4 Back gt Case Management Contents Help Top To cope with the possibility of many scenarios that you may wish to pose 3D GeoModeller introduces the concept of Case Management This is common to both GUI and batch thinking A 3D GeoModeller Case is a collection of the data components that are common to a set of Runs A geology reference model The associated characteristics of the geological formations e The one or more geophysical grids to be used jointly The specification of the voxel divisions of the geology model Use the NewCase and CaseControl commands to create and then configure a 3D GeoModeller Case Conceptually one would use these commands to set up a particular Case and then perform a series of Runs based on that Case In general once you have commenced Runs on a given Case you would not modify the Case properties Instead if changes are required you would create another Case with the required new Case properties and then perform further Runs on that new Case The components and properties of a Case are A Case geology model which is a copy of a 3D GeoModeller Project copied to
178. options in any sub task RunControl lexicon from the protobuf definition file Here are all the options as defined in the lexicon for the fuller batch language As you can see many of the parameters have default values and most parameters are optional message RunControl_GMT required string filename lt filename gt required string run lt Run gt optional string case lt CASE gt options for geological body changes optional ShapeRatioTest_GMT ShapeRatioTest 4 optional VolumeRatioTest_GMT VolumeRatioTest 5 optional CommonalityTest_GMT CommonalityTest 6 optional CommonalityVolumeTest_GMT CommonalityVolumeTest 7 optional DilationOrErosionFilter_GMT DilationOrErosionFilter 8 optional HomogeneousFilter_GMT HomogeneousFilter 9 options for lithology property changes optional PropertyInitialiseStyle LithologyInitialiseStyle 10 default FromModel optional PropertyInitialiseStyle DensityInitialiseStyle 11 default FromLawMean optional PropertyInitialiseStyle SusceptibilityInitialiseStyle 12 default FromLawMean optional PropertyInitialiseStyle RemenantMagnetizationInitialiseStyle 13 default FromLawMean optional string property _voxet 14 if using a voxet to initialise the properties optional string property voxet_field 15 options for numerics boundaries etc optional bool AllowNeighbourPropertyDifferentCheck lt DIFFERENT gt default false optional bool AllowGeophysi
179. opy e lt Run gt an alphanumeric string or identifier that will uniquely identify this run e NumberOflterations lt Number Iterations gt sets the number of iterations for the inversion Run lt Seed gt Seed is an integer to seed the random number generator For Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 101 Conients Help Top Contents Help Top lt 4 Back gt reproducible results during testing lt CHANGEONLY gt ProbabilityOfPropertyChangeOnly lt 0 100 gt Default 50 means 50 chance of doing a property change only and 50 chance of possibly changing a boundary 100 does property changes only never a boundary change lt PRESERVE gt PreserveTopology lt true false gt 0 No 1 default Yes do perform the preserve topology tests Recommend turn OFF lt OUTMISS gt SetOutputMisfits lt true false gt 0 default No 1 Yes do write the global misfit values to a misfits file once every 5000 iterations lt OUTCOMM gt SetOutputCommonality lt true false gt 0 default No 1 Yes do write the Commonality misfit values to a misfits file at every iteration lt PROPFIX gt AllowPropertyChangeOnFixedCell lt true false gt 0O No 1 default Yes the properties of fixed lithology voxels can be modified lt DIFFERENT gt AllowNeighbourPropertyDifferentCheck lt true false gt O No 1 default Y
180. or x gt 0 The probability density function is 5 x B x exp 2 Where x is the Commonality Misfit function defined below We would typically use k 1 for Commonality in which case it reduces to an exponential PDF The expected value is x F 1 1 k where F is the gamma function If we were 80 confident in the location of a formation we would specify Weibull 0 25 1 for Commonality Same j Ref Commonality j 1 C lity MisfitG _ _ PET SED Commonality j Refi _ Same j where j is the index for a movable formation means the length or number of elements is the set of voxels assigned to this formation in the reference geological model and is the number of voxels in the intersection between the set of voxels in the current model assigned to this formation and Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 68 Contents Help Top 4 Back gt For a Rayleigh distribution the probability density function is given by ratio 1 ratio 1 ra er Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 69 Contents Help Top lt 4 Back gt A Weibull distribution has Weinbull A x where 2 gt 0 is the scale parameter and gt 0 is the shape parameter It is defined for Commonality Misfit gt 0 The probability dens
181. ormation present in the Case project XML file Example In this example below there are 10 formations in the computed model so the PreserveVerticalRelationship properties form an 10 by 10 matrix that is populated by zeros by default Each row entry corresponds to an independent PreserveVerticalRelationship command for the program to process The name of the formation is referred to here as the source formation The zeros and ones in braces correspond to the target formations They are interpreted by the program as being ordered from youngest to oldest from left to right based on the formations in the computed Case project It is helpful from a visual perspective but not essential if the user provides a complete set of PreserveVerticalRelationship statements for the computed formations in the Case project one after another ordered from youngest to oldest PROTOBUF EXAMPLE First two entries only to show the preserve syntax SetLaw LithologyProperty lithology h_CAMBRIAN property Susceptibility ProbabilityDistributionFunction type LogNormal mean 0 0009 stddev 0 00004 preserve node false false false true true true true true true true LithologyProperty lithology g SOUTH_NICHOLSON_GROUP property Susceptibility ProbabilityDistributionFunction type LogNormal mean 0 0019 stddev 0 00004 preserve node false false false false true true true true true true A value of true for an e
182. ormation in the SetLaw ShapeRatio CaseControl command This option holds the surface volume ratio constant still allowing the object to grow or shrink A proposal that would eliminate the last remaining voxel for a formation is automatically rejected if this test is activated SetShapeRatioTestWeights The SetShapeRatioTestWeights command sets different weightings to control the way in which the ShapeRatioTest is applied LocalAbundance gives rise to probBack values equal to the number of voxels in the face neighborhood equal to the old lithology divided by 6 and probForward values equal to the number of voxels in the face neighborhood equal to the new lithology divided by 6 IncludeAboveTopoFaces nShapeRatio IncludeAboveTopoFacesInShapeRatio controls whether voxels in contact through a face to a voxel of the AboveTopo lithology contribute to the Shape calculation used in the ShapeRatio geological test IncludeOutsideFacesInShapeRatio IncludeOutsideFacesInShapeRatio controls whether voxel faces forming part of the outside of the mesh contribute to the Shape calculation used in the ShapeRatio geological test AllowVolumeRatioTest VolumeRatioTest is a geology test applied during the inversion This restricts the object to a certain size SetVolumeRatioTestWeights The SetVolumeRatioTestWeights command sets different weightings to control the way in which the VolumeRatioTest is applied localAbundance
183. oss the model The frames are initially standard JPEG jpg image files The final movie is an AVI avi file which can be played on a range of Windows movie players such as Windows Media Player QuickTime Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 139 Conients Help Top Contents Help Top 4 Back gt MakeSectionMovie lt Run gt lt SweepLineCoordinates gt lt MovieControl gt lt NoFramesAlongSweep gt lt MaxSectionWidth gt GetField lt DerivedVoxet gt lt FieldWithinDerivedVoxet gt lt ColourScheme gt lt ScaleOption gt lt OutputFilename gt where lt CaseXML gt the relative or absolute path of the XML project file for the 3D GeoModeller inversion Case lt Run gt an alpha numeric string or identifier that identifies the inversion Run lt SweepLineCoordinates gt lt FromEast gt lt FromNorth gt lt ToEast gt lt ToNorth gt and define the Start and Finish end points of the sweep line through the 3D Project lt MovieControl gt lt MaxCols gt lt MaxRows gt lt VerticalExaggeration gt lt FramesPerSecond gt lt QualityPercentage gt where lt MaxCols gt the maximum number of pixels across the JPEG image of the Section see further note lt MaxRows gt the maximum number of pixels down the JPEG image of the Section see further note lt VerticalExaggeration gt typicall
184. oxet produce an image of a field on a section lt Output gt message MakeSectionImage_GMT required string filename lt CaseXMI gt optional string case 2 optional string run 3 not used for forward modelling optional string products 4 use this for forward modelling to find output voxets required GetFunction_GMT get_function 5 required string Section lt Section gt optional int32 MaxPixelCols lt MaxCols gt default 500 optional int32 MaxPixelRows lt MaxRows gt default 500 optional double VerticalExaggeration lt VerticalExaggeration gt default 1 0 optional int32 QualityPercentage lt QualityPercentage default 100 optional ColourScheme lut lt ColourScheme gt default Colours optional ScaleOption_GMT Scaling lt ScaleOption gt optional string image lt OutputFile gt placed in the local directory SectionImage_verticalExag_fieldName_SectionName where lt CaseXML gt the relative or absolute path of the XML project file for the 3D GeoModeller inversion Case GetField lt DerivedVoxet gt lt FieldWithinDerivedVoxet gt extracts data for a specified Field from a specified Voxet There must be no spaces within the Q e lt DerivedVoxet gt any 3D project voxet which is derived from the 3D GeoModeller Project e lt FieldWithinDerivedVoxet gt is a Keyword as used in the voxet header file such as Lithology MostProbable MostProbableThresholded Mea
185. oxets because of surface roughness the effective variation is much less 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 119 Contents Help Top lt 4 Back gt PreserveVerticalRelationship Introduction The computed formations in a Case have a vector property termed PreserveVerticalRelationship This property is used in a geological test that is applied during a geometry optimisation inversion Run to enforce normal upward younging young over old or reversed overturned old over young relationships between any pair of formations The following image is from the third page of the Inversion wizard It shows the point where you can select each lithogy unit in turn and then impose rules on how that unit can change The main talking point here is Allow above these Lithologies If you check on another unit its relationship with the current principal in turns of vertical relationship can be forced Lithology specific settings Lithology Properties Foc thology Foner Host Constraints Commonality Veibull 0 0010 1 0 100 Commonality volume Normal 0 0 1 0 100 Shape ratio jNormal 0 25 0 05 100 Volume ratio JNormal 0 25 0 05 100 Always above these Lithologies Slab l Stratigraphic Order Reset SetLaw In batch a CaseControl task contains SetLaw which in turn conatins the LithologyProperty sub clause This is used to assign the
186. parameter that is specified in the NewRun command is the number of inversion iterations to be performed this RunControl command allows the user to modify that Seed This sets the seed for the random number generator This is designed to generate reproducible results during testing and for research purposes Intrepid s internal testing uses this to compare the results generated from the current Build of the software with historical results The single parameter lt seed gt is any long integer The default of course is to not set a seed and thus get random results from different Runs ProbabilityOfPropertyChangeOnly The default value for the ProbabilityOfPropertyChangeOnly is 50 which means a 50 chance of doing a property change only no change to a voxel s lithology and a 50 chance of possibly changing a boundary by changing a voxel s lithology Setting this to 100 will generate a Run which does property changes only and never changes any geology boundaries Recommended to do a test run with ProbabilityOfPropertyChangeOnly 100 to test the behavior of the inversion for this scenario of only properties being allowed to vary and there being no lithology changes PreserveTopology PreserveTopology is a topology test implemented in early versions of 3D GeoModeller and was designed to ensure that the topology of the initial geology model was maintained by not allowing any body to split into two
187. per bounds also require the observed geophysical geophysical field to match a best fit message Property Optimization_GMT required string filename 1 project xml required string case 2 required string run 3 optional string ReportFile 4 default Property Optimization rpt optional SetLaw_GMT SetLaw 5 optional double maxAbsoluteObserved 6 method to ignore observered data spikes when doing property observations optional bool EstimateDensity 7 default true optional bool EstimateSusceptibility 9 default false optional int32 MaximumIterations 10 default 10000 stop the Levenberg Marquardt solver if no good soultion found PROTOBUF EXAMPLE InversionTask Property Optimization filename InputGeology CF83 CF83 xml1 SetReferenceLithology initial_lithology vo case Casel_Susc run runl Parameter to avoid spikes in observed grid maxAbsoluteObserved 30000 EstimateSusceptibility true EstimateDensity false SetReferenceMagneticField Magnitude 50000 Inclination 65 0 Declination 25 LithologyProperty lithology Slab property Susceptibility ProbabilityDistributionFunction type LogNormal mean 0 001 stddev 0 000001 lower_bound 0 001 upper_bound 0 01 LithologyProperty lithology Host property Susceptibility ProbabilityDistributionFunction type LogNormal mean 0 000001 stddev 0 000001 lower_bound 0 001 upper_boun
188. physics data is much enhanced Advanced API access During 2010 2011 a couple of PhDs have been published Monash amp Curtin Universities that concentrate on quantifying geological uncertainty rather than the whole geology geophysics uncertainty mix The students have made use of the 3D Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 9 Conients Help Top Contents Help Top q Back gt GeoModeller published C API to directly construct geology models programmatically then compute the surfaces and quantify the spatial uncertainty in 3D In one case this was done using a Python wrapper to call the C engine room capabilities No C callable API exists for the main Inversion dll s though with the new unified protobuf interface the dll s that all the functions use is accessible by external programs provided they construct their own messages and pass these to the library functions Google publish all the technology to generate C Java and Python bindings to do this job See http code google com apis protocolbuffers docs tutorials html 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 10 Contents Help Top lt 4 Back gt Status of Geophysical Tools As at 3D GeoModeller v2012 the majority of inversion thinking and controls detailed in this manual are available in the new GUI wiza
189. ple task files Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 80 Contents Help Top lt 4 Back gt ForwardModelFromCase The ForwardModelFromCase command computes the geophysical responses of a Case The command simply executes the process of computing the required geophysical responses It is expected that the required computation task has been fully specified in the various parameters of the Case These parameters see below are set by the NewCase and the CaseControl commands ForwardModelFromCase lt OutputPrefix gt where lt CaseXML gt the relative or absolute path of the XML project file for the 3D GeoModeller inversion Case e lt OutputFilePrefix gt the prefix of the output geophysical response grid files and optionally the relative or absolute path of the output directory The full output filename uses the supplied prefix together with the Geophysics Type Keyword designating the geophysical data type Gravimetry or Gz Gee Gen Ged Gnn Gnd Gdd Magnetism or TMI Me Mn Md Mee Men Med Mnn Mnd Mdd Tensor grids of magnetic and or gravity gradients are also supported The Case itself must contain the full specification of the task to be performed This task is described in terms of the following parameters The source 3D geology model The Case s lithology voxet derived from a 3D 3D GeoModeller Project is
190. pretations and reconciliations Examples of such datasets are aeromagnetics 2D seismics and Full Tensor Gravity gradiometry In 3D GeoModeller v2012 we now support a full range of regular semi regular and random point and surface datasets This has meant that the 3D GeoModeller Explorer now has options to fully visualize any of the grids surfaces in 2D or 3D used for modelling simulation and inversion Histograms Data Clipping Data Colour Lookups Statistical reports and Iso Surface queries are now easy and part of the normal workings of 3D GeoModeller As we have a comprehensive way for you to manage your exploration of the link between geology and geophysics datasets there are options to ensure your Data Tree explorer and your reults viewer are automatically seeing all the transient workings If this does not seem to be happening we provide a fall back for you to search and add any of these outputs to your Tree You can also manage the complexities by deleting unwanted simulations as you desire The aim has been to also provide you with ways to visualize using the latest GPU enhanced graphics very large Mesh Grid datasets in the context of your implicit geology model and to export any of the standard outcomes to a format suitable for your needs External Geology Models There are new relaxed rules for supplying a geology model in order to make use of the 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt
191. rds and also via the protobuf control language The V1 3 job control language is obsolete and not supported in any way from 3D GeoModeller 2012 onwards The tool to execute these old commands no longer ships The replacement tool is invbatch The language is superficially the same but greatly extended The detail syntax is however quite different and more explicit The new parser is capable of exact error reporting down to line and column The software tools associated with 3D GeoModeller are 1 Geomodeller exe 1 38D Geology Create or Edit or Visualize 2 Forward Model spatial potential fields solver now multi threaded 3 Forward Model spatial heat equation solver 4 Full constrained stochastic inversion via a graphical user interface 2 vfilt exe 1 Forward Model FFT 3D potential fields solver very quick multi threaded and large capacity 3 MTDyke exe 1 Forward Model for Dykes 4 jMapPrint 1 Create or Compose plans and sections laid out on paper to scale and geolocated with extra external data sets 5 invbatch exe The main tool for batch processing of geophysical tasks This tool has at least the following capabilities 1 Uncertainty studies Parameter sweep for resources basement geology 2 Rock Property determination by least squares best fit to regional geology geophysics Case Controlled Geophysical Inversion Forward Model Make Movies Make section images including geology probabilities NO om Ff W
192. re also asked to specify sampling rates 3D GeoModeller v2012 forward modeling capability includes temperature heat flow using the heat diffusion equation heat conductivity and fluid flow In 2011 underlying facet modelling code has been developed to support all aspects of this Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 4 Contents Help Top lt 4 Back gt Inversion requirement This includes the thin plate facet code for dykes All modelling code has capability for any potential field scalar vector component and the tensor curvature gradients New to 3D GeoModeller v2012 is the support for dykes The geometry of the dykes can be continuously varying in thickness and also the lithology properties could support a graded response depending upon the weathering etc At the first release of 3D GeoModeller v2012 the dyke forward modelling is still delivered as a standalone tool called MTDyke A variety of means of specifying the geometry of the dyke are supported Ultimately the design calls for a mid skeleton representation of the dyke with each facet having attributes of thickness susceptibility density etc Other than in batch mode 3DGeoModeller will autosense your computer s capabilities and use make use of these With each new version of 3D GeoModeller significant improvements are being added In the case of 3D GeoModeller v2012 multi threading
193. results and visualize them in the context of your modelling session Some options are not as easily integrated and you need to revert to the batch system to make movies for instance It is easy to capture a section image showing its geophysical response directly in the section view To do this simply choose the visualization manager option for the results voxet and then choose the sections required The same set of reports can be generated via the full set of batch tasks described below As noted in the previous Section the result of a 3D GeoModeller inversion is not a 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 129 Contents Help Top lt 4 Back gt single revised model of the 3D geology of the project area Rather the result is an assemblage of many alternate models all of which are valid geology models and are models which have a progressively better match to the geophysical data sets depending of course on your chosen inversion parameters The complete description for every one of those alternate models can be derived from a the starting geology voxel model together with b the progressive record of all accepted single voxel changes to the model as recorded in the modifications txt file This modifications file is ASCII but in practice not very useful for a human to decode It is extremely large and also very terse recording just the one change
194. rid cell centroid due to every voxel in the lithology voxel model including the padding zone This is reported as a set of initial grids in ERMapper format If specified the initial detrending is then performed Typically detrending should be requested It is designed to remove any gross differences between the observed field grid and the initial computed grid See the MatchTrend parameters in the NewCase command NewCase PROTOBUF EXAMPLE InversionTask Run filename InputGeology CF83 CF83 xml run R1 case C5 Testing true The detrending determines the difference between the two grids and subtracts that difference from the observed field grid making the continually revised computed grid more directly comparable to the observed field grid The inversion process is then initiated The details of the inversion algorithm have been published in various papers and are not described here other than to note that e each iteration of the inversion consists of proposing some change to just one voxel of the voxel model selected at random The proposed change May simply be a revised assignment of the physical property values for the existing lithology of the voxel OR May be a proposed change of lithology for the voxel together with assignment of revised physical property values for that new lithology the geological and geophysical impact of the proposed
195. right angles to each other and this primary direction Visual Tour of Geophysical Parts of 3D GeoModeller Contents Help Top Setting Lithological Properties One logical starting point is to take the geology units and give enough properties to start to have a geophysical response If all the units have the same property there will be no geophysical anomalies The default values we give to each of the possible properties for a unit is the same One convention used in 3DGeomodeller is the requirement for at least one Standard Deviation to be set to a non zero value as an indication that some thought has gone into the process See the following figures Figure 4 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 19 Conients Help Top Contents Help Top 4 Back gt fm Physical Proper Gravity Magnetic Thermal Advection Formation Density g cm WB UpperCover Normal 2 67 0 100 Bi Middlecover Normal 2 72 0 100 Normal 2 67 0 100 I Basement Normal 2 67 0 100 Density Mode Bi modal X Description Unit g cm Normal 2 67 0 80 Normal 3 4 0 2 20 Definition of the mode component Law simulation Mean Standard deviation Statistical law Percentage of Population General Parameters Definition of the mode component Density Reference Density g cm Mean
196. robability Distribution Function PDF lt STDDEV gt The standard deviation of the Probability Distribution Function PDF e lt PERCENT gt The standard deviation of the Probability Distribution Function PDF 100 signifies 100 for this uni modal case e lt DECLIN gt The declination of a the remanent magnetisation vector direction if a required property lt INCLIN gt The inclination of a the remanent magnetisation vector direction if a required property e lt VOXET gt This allows you to specify a predifined property voxet distribution e lt FIELD gt Field to use in a predifined property voxet distribution For a bi modal or tri modal distribution lt PropertyLaw gt has the following syntax e lt PropertyLaw gt lt StatisticalLaw gt Mean1 StdDev1 Pcent1 lt StatisticalLaw gt Mean2 StdDev2 Pcent2 For example SetLaw LithologyProperty lithology Slab property Density ProbabilityDistributionFunction type Normal mean 3 67 stddev 0 01 percentage 45 ProbabilityDistributionFunction2 type Normal mean 3 01 stddev 0 01 percentage 55 LithologyProperty lithology Host property Density ProbabilityDistributionFunction type Normal mean 2 67 stddev 0 01 The tri modal syntax is similar with a third lt StatisticalLaw gt defined But see details in Illustration of dual mode property law settings and SetLaw Type 2 Inversion Control Propert
197. rt Make sure you can find any similar report you may have generated This is one of the primary fall backs you have to record what has been going on during the possibly many scenarios Start Inversion run 19 6 2007 38 39 11 using cut 135 Modifications File C PROC SHELL_INVERSION_CRB_FTP_DATA Shell_Inversion_From_Voxet_Gravity 3_WorkHere Results Case_Initial_Voxet_Lateral_Control Case_Initial_Voxet_Lateral_Control_Run_1_modifications txt Iterations 100000 Seed 1182217147 OBSERVED Gravimetry GRID C PROC SHELL_INVERSION_CRB_FTP_DATA Shell_Inversion_From_Voxet_Gravity 3_WorkHere Results Case_Initial_Voxet_Lateral_Control resampled_TZ Bouguer267_UC5000_WF4 ers at 1146 500000 1 1 0 Formation Dummy Index 1 Density Normal 2 67 0 100 Formation Mio_basalt Index 2 Density XY 2 67 0 0001 100 InputGrids resampled _Basalt_Density ers Formation Tert_sediments Index 3 Density XY 2 67 0 0001 100 InputGrids resampled_Sediment_Density ers Formation Jur_basement Index 4 Density XY 2 67 0 0001 100 InputGrids resampled_Basement_Density ers Formation Lwr_crust Index 5 Density Normal 2 9 0 0001 100 Formation Sub_moho Index 6 Density Normal 3 25 0 0001 100 StartLithology C PROC SHELL_INVERSION_CRB_FTP_DATA Shell_Inversion_From_Voxet_Gravity 3_WorkHere InputGeology voxets EF_VOXET_regions_m_1 vo StartDensity C PROC SHELL_INVERSION_CRB_FTP_DATA Shell_Inversion_From_Voxet_Gravity 3_WorkHere InputGeology voxets CRB_
198. rth east down NED right hand e lt OutputFilePrefix gt the prefix of the output geophysical response grid files and optionally the relative or absolute path of the output directory The full output filename will use this supplied prefix together with the Geophysics Type Keyword designating the geophysical data type Gravimetry Gee Gen Ged Gnn Gnd Gdd Magnetism Me Mn Md Mee Men Med Mnn Mnd Mdd where e east e n north d down in a right hand coordinate system This command was designed to compute the geophysical responses of any voxet with the required physical properties data However some of the necessary parameters such as the details of the Earth s Geomagnetic Reference Field are not recorded in the voxet files For this reason certain computation parameters are passed or default values assumed or derived from the voxet Geophysics computation parameters derived from the specified Geology Model Voxet are The physical properties for each voxel in the voxet model such as Density and Susceptibility The grid geographic details the grid extent grid cell size and grid cell position Geophysics parameters defaulted the reference density Gravity responses are computed using density contrasts for each lithology relative to this specified reference density The default value is 2 67 g cm Geophysics parameters supplied on the command line The ambient magnetic field of the Earth fi
199. s 0 0 0 5 Gaussian Normal distribution Log Normal Distribution For constraining the geometry of the geological bodies their volumes a Weibull probability distribution function is introduced to give access to more appropriate rules The Weibull distribution has gained a large following in the automotive industry as a means of predicting mean time between failures for car component parts The property sought is that the initial starting model should have a high probability of being right This follows from the proposition that the geologist knows what he is doing and the reference model is close to the truth 100 204 60 40 Same as the reference model Weibull probability distribution 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 37 Contents Help Top lt 4 Back gt The need for a Close Starting Model One of the central issues needed for a successful use of the fully constrained lithological inversion method is to create a starting or reference model that is not only consistent with all the geological observations but also close to honoring the observed geophysics signals for the majority of your study area The simple reason for this requirement follows from the use of Monte Carlo techniques which will not converge to an appropriate solution if the initial model is grossly incorrect There is a very detail process of changin
200. s The protobuf syntax for this command is Create a Set of Fixed Cell in any part of your model space for an inversion run eg due to observed outcrop geology or drill hole observations If SetFixedCells is never called the default is to set all the cells of the layer at the highest elevation to fixed When the first call of SetFixedCells is made this program default is cleared i e equivalent to a call of SetFixedCells CLEAR II and a voxet named lt Case gt _ lt Run gt _modifiable vo is established with all values of the Modifiable property initialised with 1 All subsequent SetFixedCells calls are additive message SetFixedCells_GMT required string filename 1 required string run 2 optional string case 3 optional string xyzfile lt XYZ_Filename gt accept a set of X Y Z coordiantes for cells to be fixed optional bool CLEAR lt CLEAR gt default false clear out any prior fixed cells optional bool MappedObservations lt OBSERVED gt default false fix any cell that contains a geology contact optional RepeatedObservedReliability_GMT goodness lt GOODNESS gt eg goodness formation sandstone reliability Observed would fix cells that have contact data with this attribute optional ctm RepeatedString geology lt FORMATION gt a way to fix whole geology formations eg you have good seismic control near surface Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp
201. s of difference between the observed field grids and the model computed grids for each of the geophysical data types being inverted is also recorded in the modifications txt file 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 128 Conients Help Top q Back gt Extensions to Run on a super computer or Cluster situation Reporting Contents Help Top The idea is is to have a Master process that distributes the geophysics forward mod elling aspects to many SLAVE nodes and also breaks up the domain into vertical slices As we are using spatial prism based methods for calculating the response effi ciencies are mostly got by precomupting the kernel responses and saving these in memory for re use trial confirm a near linear reduction in elapsed time versus the number of Nodes Multi threading of the calculations is also being used Check Point Restart has been implemented so that more flexibility on managing simulations is achieved Files capture the state of the simulation at regular intervals in the course of the run These are stored in a sub directtory under Case Run CheckPoint The number of iterations that were used at the time of the checkpoint are recorded in the checkppoint txt file and a restart from there for the requested further number of iterations can be made without having to repeat the earlier work Inversion stops when the specified n
202. sion of the uncertainty with larger values indicating greater uncertainty in the arrangement in the reference model Use of gt 1 indicates that we are absolutely certain that the arrangement in the reference model is wrong but that the arrangements to be sent for evaluation should still have a degree of similarity with the reference model The arrangement in the reference model has a zero probability of being sent for evaluation In mathematical terms for k 1 the Weibull distribution is identical to an exponential type distribution with the PDF for Commonality Misfit 0 Commonality 1 being 1 4 For x 1 eps the Weibull distribution begins a transition to more bell shaped distributions such as the Rayleigh distribution and the PDF for Commonality Misfit 0 is 0 The mode peak of the PDF is at x pow k 1 k 1 for K gt 1 For 1 this peak is at zero With gt 0 and constant A the peak moves to increasing values as x increases Note that for k 2 the Weibull distribution is identical to a Rayleigh type distribution For example LithologyProperty lithology Air property Commonality ProbabilityDistributionFunction type Weibull mean 0 001 stddev 1 LithologyProperty lithology Water property Commonality ProbabilityDistributionFunction type Weibull mean 0 001 stddev 1 LithologyProperty lithology SedUpper property Commonality ProbabilityDistributionFunction type Weib
203. sity SetReferenceMagneticField SetReferenceDensity default 2 67 g cm sets the Reference Density value in units of g em The density contrast for each lithology is determined relative to this Reference Density The Reference Density is typically set to the Bouguer density value See SetReferenceDensity Default 2 67 gicm 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 53 Conients Help Top 4 Back gt e SetReferenceMagneticFieldMagnitude default 50000 nT specifies the Earth s magnetic field intensity in the Project area Units are nanoTeslas nT See SetReferenceMagneticFieldMagnitude Default 50000 nT SetReferenceMagneticFieldInclination default 90 0 specifies the inclination of the Earth s magnetic field in the Project area Inclination is positive in the northern magnetic hemisphere negative in the south If using RTP data set inclination 90 See SetReferenceMagneticFieldInclination Default 90 degrees e SetReferenceMagneticFieldDeclination lt value gt default 0 0 specifies the declination of the Earth s magnetic field in the Project area See SetReferenceMagneticFieldDeclination Default 0 degrees SetReferenceLithology lt ReferenceLithologyVoxetPath gt the relative or absolute path and filename of a reference Voxet geology model This Reference Lithology Voxet is used by the commonality tests
204. sting each proposal This function is called in a series of loops to apply the PreserveVerticalRelationship test to an entire voxet If the PreserveVerticalRelationship test is activated for a Run the Reference and Initial lithological models are completely scanned during the initialisation phase of Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 121 Conients Help Top LithologyProperty preserve lt 4 Back gt the Run to provide feedback to the user regarding the degree of conformity in these models to the specified relationships This information is written to the inversion_debug RPT file The final lithological model is also scanned at the end of the Run with the outcome reported in this RPT file The PreserveVerticalRelationship test is performed whenever a single voxel change in formation assignment is proposed It is the first of the geological tests to be carried out because it is computationally simple and a hard constraint i e results in outright acceptance or rejection Assuming that the proposed new formation is the M th formation a check is made that none of the formations with a True flag as defined in row M of the PreserveVerticalRelationship matrix are present above the voxel location In addition a check is made that none of the formations with a True flag as defined in column M of the PreserveVerticalRelationship matrix are pres
205. t must be considered SetUseTopo Take Topography into Account The CaseControl SetUseTopo command should almost always be executed so that the geology model is clipped by the topographic surface In the Voxet geology model created by the NewCase command the lithology for each voxel is defined by an integer in the range 1 n for the n different lithologies in the Project Note that by default 3D GeoModeller ignores topography and modeled geology extends into the sky See Figure 17 b Executing SetUseTopo 1 updates the inversions xml file UseTopo false to UseTopo true modifies the Voxet and assigns lithology code 0 to all voxels with their centroid above the topographic surface In effect a new lithology is created and it is assigned default physical property values 0 for susceptibility and remanence but density is set to Reference Density value default 2 67 g cm See Figure 17 c The SetAboveTopoDensityLaw SetAboveTopoDensity must be used to assign 0 density to this above topo region See Figure 17 d See also the discussion at Gravity Dataset and Topography Considerations you may want to fill the valleys Figure 17 Use of the NewCase SetUseTopo and SetAboveTopoDensity commands 3D GeoModel ler modelled geology contacts ignore the topographic surface a By default the Voxet produced by a NewCase command also ignores the topography b and voxels repre sent
206. tType 0 CommonalityVolumeWeightType 0 NewModFormat true VolumeRatioWeightType 0 PreserveTopology true OutputMisfits true AllowAdaptiveFilter true InitialDensityVoxet String ShapeRatioWeightType 0 AllowPropertyChangeOnFixedCell true AllowDilationOrErosionFilter true AllowCommonalityTest true LithologyInitialiseStyle 0 AllowCommonalityVolumeTest true LargeMisfitRMSThresholdFactor 3 141593 Seed 2 RemanentMagnetisationInitialiseStyle 0 HomogeneousFilterRate 0 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 155 4 Back gt 4 Back gt GeoModeller User Manual 156 Conients Help Top Contents Help Top 4 Back gt AllowVolumeRatioTest true DilationOrErosionFilterRate 0 PriorOnly true DensityInitialiseStyle 0 Name String InitialSusceptibilityVoxet String IncludeOutsideFacesInShapeRatio true InitialLithologyVoxet String ResponseFilterType 0 AllowNeighbourPropertyDifferentCheck true OutputCommonality true ProbabilityOfPropertyChangeOnly 0 SusceptibilityInitialiseStyle 0 AllowHomogeneousFilter true NbIterations 2 InitialRemanentMagnetisationVoxet String LargeMisfitTemperature 3 141593E0 IncludeAboveTopoFacesInShapeRatio true AllowShapeRatioTest true RunResult FinishedDateTime String InterProposalCount 0 VolumeTestCount 0 ShapeRejectCount 0 CommonalityTestCount 0 ProposalCount 0 PreserveTopologyTestCount 0 PreserveTopologyRejectCount 0 IntraProposalCount 0 IntraAccepta
207. tails to supplement the definitions in the above Syntax Dataset Requirements Geology Project 3D GeoModeller uses a 3D GeoModeller Project as the primary source of knowledge about the geological structural of the project area The 3D GeoModeller Project also serves as the source of the surface topography See Surface Topography Note however that it is possible to perform an inversion with a Gocad geology model provided the extra information needed is also presented The main requirements for the 3D GeoModeller Project are The model must have been computed This means that if any last minute edits are performed in 3D GeoModeller the model must be recomputed before using that Project for geophysical forward or inverse modelling Ifthe reporting of inversion results will use images of inversion geology results or movies of the inversion s evolution of the model on sections then those sections must have been previously created in the 3D GeoModeller Project Both traditional vertical sections and horizontal slice sections may be created and used in the reporting of inversion results An external Gocad voxet is used to create a 3D GeoModeller project via the New command Once a project is created sections can be added to the project so that you can use these to create images and movies that are geolocated 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 42 Coni
208. tes Pty Ltd 4 Back gt GeoModeller User Manual 87 Contents Help Top lt 4 Back gt formation index 5 field granites1 InversionTask Property_Parameter_Sweep filename testArea_2suites_imported testArea_2suites_imported xml output_stub_name stochastic_ BoundaryConditionToSweep location Base BoundaryStyle Boundary _ HeatFlow LithologyPropertyToSweep lithology aboveC property ThermalConductivity LithologyPropertyToSweep lithology ZtoC property ThermalConductivity LithologyPropertyToSweep lithology BLS property HeatProductionRate LithologyPropertyToSweep lithology granites1 property HeatProductionRate Number _ CPUs 5 Number Permutations 2 GenerateTasks_ThenStop true ThermalUncertaintyStudy filename testArea_2suites_imported testArea_2suites_imported xml case Case_1 input_voxet testArea_2suites_sub2 vo field alias alias Lithology field Lithology Advanced true Surface_Temperature_Law type Log_normal mean 22 stddev 0 hold this one constant Base _Heatflow_Law type Log_normal mean 0 036 stddev 0 005 this is the one we want to vary from above SetLaw LithologyProperty lithology aboveC property ThermalConductivity ProbabilityDistributionFunction type Normal mean 2 0 stddev 0 2 vary LithologyProperty lithology ZtoC property ThermalConductivi
209. th the AboveTopo cells are all fixed Also note that SetFixedCells still allows PropertyOnly resampling to occur at these cell locations for example InversionTask SetFixedCells filename InputGeology CF83 CF83 xml case C5 run R1 CLEAR true SURFACE true 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 124 Contents Help Top lt 4 Back gt Executing Geophysical Tasks RUN Having used the NewCase and various CaseControl commands to create and specify a Case and the NewRun and various RunControl commands to create and specify a Run The required geophysical task is then executed with the Run command Execution Environment Settings Execution Interactive Batch Use profile local Number of Cores Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid lt 4 Back gt GeoModeller User Manual 125 Conients Help Top 4 Back gt Formal definition of a RUN Contents Help Top arun has specific controls set within the confines of the more general case e arun can hold the geology constant and just perturb the properties aruncan force the stochastic process to reject overturned geology for certain units arun can select from all the possible topological operators what mix and what variation to allow arun can impose a set of fixed or unchangeable parts of your geology mod
210. thMIN_VOXET NNORTH x nCELLSIZE gt NorthMAX_VOXET In addition to the command line parameters above the following required details must be correctly specified within the 3D GeoModeller Project itself The source 3D geology model is the computed model in the 3D GeoModeller Project This describes the set of lithologies to be used and their distribution in 3D space The voxelisation of the Project is specified by command line parameters above to determine voxel size and the computed model vertical extents East and North extents are derived from the Project extent The physical properties distributions for each of the lithologies in the Project The reference density Gravity responses are computed using density contrasts for each lithology relative to this specified reference density The ambient magnetic field of the Earth field strength inclination and declination Note that the forward model will include the effects of the border padding see IncludeBorderFEffect Note that the geographic details of the required output grids the grid extent grid cell size and grid cell position are determined from the voxel model that is generated the grid geometry is determined from the extent of the 3D GeoModeller Project and the eCellSize and nCellSize parameters Batch example invbatch batch forwardmodel task This would be executed in a command window In the following sections we show exam
211. the Section started to break up for example one would probably conclude that such a geology cross section was not realistic that geology simply does not look like that Such behaviour in the evolution would suggest that the inversion constraints designed to keep the geology realistic were failing to achieve their designed goal and a new inversion Run with revised parameters might be required Analyse or consider the geology on the Section If one assumes that the movie is presenting literally hundreds of alternative valid geology cross sections then the skilled geologist should expect to integrate the set of rapidly presented alternatives and apply their geological knowledge to consider the likelihood that the presented geology sections are realistic or not and also contemplate the geological processes that might have generated such geological structure and whether such processes are realistic processes that may have operated during the geological history of that Project area PROTOBUF EXAMPLE InversionTask MakeEvolutionMovie filename InputGeology CF83 CF83 xml Runinterval run R1 case C5 start_iterations 10000000 end_iterations 20000000 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual Conients Help Top Contents Help Top 17_VE3 132 lt 4 Back gt IterationIncrement 40000 show Geology MaxPixelC
212. ticular formation ShapeRatio is the ratio of the Shape of the present model divided by the Shape of the same formation in the reference model We might expect that the ratio of present to reference values for a collection of models where the regions for each formation have similar shapes might be a population with a LogNormal distribution A specification of LogNormal 0 0 05 would indicate a mean VolumeRatio of 1 and a standard deviation of 5 Due to the competing influences of many constraints this tight specification would be unlikely to be achieved but might produce a satisfactory constraint over the ShapeRatio values observed in the proposed models For Property VolumeRatio Syntax Formation VolumeRatio lt StatisticalLaw gt where lt StatisticalLaw gt lt Normal LogNormal Poisson Equal EqualPlus EqualMinus Weibull Rayleigh gt e Associated parameters Mean StandardDeviation VolumeRatio is defined as the ratio of the number of voxels in the present model assigned to a particular formation divided by the number of voxels assigned to this formation in the reference model We might expect that the VolumeRatio for models with similar proportions might be a population with a LogNormal distribution A specification of LogNormal 0 0 01 would indicate a mean VolumeRatio of 1 and a standard deviation of 1 Due to the competing influences of many constraints this tight specification would be unlikely to be achieve
213. to a Voxet with voxels having some discrete voxel dimension All the 3D GeoModeller v2012 software is also deployed upon various cluster super computers and there the practical limit for inversion is more like 100 million voxets in a time frame of 7 days This does not allow for a high resolution inversion on the scale of the whole of Australia where the aim is to have around 250 million voxets to get 20km resolution for crustal mantle scale studies It is expected this will be achieved in the 2012 In contrast a high resolution magnetic survey will frequently detect signatures from magnetic geology bodies which are much narrower than the model s voxel dimension In other words magnetic bodies that simply cannot be effectively represented in the Voxet geology model Recommendations Apply an upward continuation to the data and perform an inversion on the regional scale model OR perform an inversion on a more detailed model of limited extent and consider using the new dyke features in your model Provision is made for periodic trend matching to reduce the reliance of the outcome on the choice of long wavelength trend through the data as it is difficult to predict the appropriate base level and trend prior to an inversion run The following procedure is used for trend matching At the first iteration we calculate the forward model response of the initial model We subtract computed from observed observed calculated We fit a
214. to remove isolated voxels islands from the model thus reducing boundary complexity Dilation turns voxels on according to rules based on the number or arrangement of neighboring voxels and erosion turns voxels off according to similar rules Opening is the application of the morphological filters erosion followed by dilation Closing is the reverse sequence dilation followed by erosion Morphological operations are analogous to convolutions performed by systematically passing a small 3D structural element cf kernel across the lithology voxet at some specified points in the inversion run These structural elements are typically 3 x 3 x 3 operators See Introduction for examples and also Illustration of dual mode property law settings 3D GeoModeller DilationOrErosionFilter applies the dilation or erosion operators in a directional sense and has the effect of advancing or retreating a boundary by one voxel and at the same time achieving a degree of topological smoothing Thus the primary purpose of this filter is as a method for proposing a global boundary perturbation to migrate and reshape a boundary See more notes at Dilation and Erosion Morphological Filters The Homogeneous Filter combines the open then close morphological operations in an attempt to restore the original surface area of some geology region or volume but with some rearrangement of the boundary voxels This it is specifically a smoothing filter designed to balanc
215. to the data Thus the topography should be modelled as follows With the NewCase command set the lt zMaxVoxet gt value to be at the highest point of the topography With the SetUseTopo meaning use the topography IncludeBorder Effect The default is to use the topography In batch Use the SetAboveTopoDensityLaw to specifically assign the density of the region above the topography to have the density value that was used in applying the Bouguer correction to the data SetAboveTopoDensity If the Reference Density has been set to that same value then that correct value is used as the default value for the above topo region and the SetAboveTopoDensityLaw would not need to be specifically used See Figure 15 Note also the recommendation to set the elevation of computation of the geophysical solutions to be well above the top of the top voxel of the model It can be useful to use the first vertical derivative 1VD of a gravity dataset for forward modelling or inversion The advantage of the 1VD is that it can enhance subtle anomalies due to a local gravity source and it reduces the long wavelength component in the data Since these wavelengths may reflect sources outside the volume under investigation use of the 1VD reduces the reliance on knowing the correct regional response The disadvantage it can also enhance noise signatures The 1VD of gravity is the rate of change of gravity in the downwards directio
216. ty We need to make a distinction between the properties of a case and those of a run The case properties specify geological data or knowledge what are the things that we know The run properties will manage the behaviour or progress of the inversion as it explores that space of alternative model scenarios testing their validity against the geophysical datasets Note that one would typically perform a series of inversion runs on a given case In general having commenced inversion runs on a case do not modify the case properties Instead you might create another case with the required new case properties and then perform further inversion runs on that new case The main components and properties of a run are A specified number of iterations How the lithology and physical property values are to be initialised Whether to apply morphological filters or not e Whether to apply other inversion constraint tests such as tests designed to maintain the shape of a geology body or tests to restrain model shapes to retain a similarity to some reference set of shapes If more than one geophysical data type is specified the acceptance test can be carried out using the combined normalized data misfits for multiple input grids or by applying a sequence of Metropolis acceptance tests to the data misfits for each grid Mosegard and Tarantola
217. ty lt Property gt ProbabilityDistributionFunction_GMT ProbabilityDistributionFunction lt PropertyLaw gt ProbabilityDistributionFunction_GMT ProbabilityDistributionFunction2 lt PropertyLaw gt bi modal ProbabilityDistributionFunction_GMT ProbabilityDistributionFunction3 lt PropertyLaw gt tri modal bool fixed 6 default false is the geometry for this litho unit moveable int32 index_voxet_key 7 index field array list to indicate possible formation below current formation a normal pile ordering is achieved with trues in the top triangle an overturned pile ordering is achieved with trues in the lower triangle optional ctm RepeatedBool preserve lt PRESERVE gt preserveverticalRelationship in the pile for this unit relative to others optional optional double lower_bound lt LOWER gt used for bounded non linear 3D property optimization double upper_bound lt UPPER gt where lt GeologyFormation gt is the name of one of the geology formations in the 3D GeoModeller Project e lt Property gt lt Density Susceptibility Remanence Commonality CommonalityVolume ShapeRatio VolumeRatio gt This in an enumerated list in the invtaskmodel proto file e lt LOWER gt Set a lower bound for the property optimization step lt UPPER gt Set a upper bound for the property optimization step e lt PRESERVE gt Preserve Vertical Relationship in the pile for this unit relative to others
218. ty ProbabilityDistributionFunction type Normal mean 1 4 stddev 0 2 vary LithologyProperty lithology basement property ThermalConductivity ProbabilityDistributionFunction type Normal mean 2 4 stddev 0 0 LithologyProperty lithology BLS property ThermalConductivity ProbabilityDistributionFunction type Normal mean 3 1 stddev 0 0 LithologyProperty lithology granites1 property ThermalConductivity ProbabilityDistributionFunction type Normal mean 3 1 stddev 0 0 heat production rate LithologyProperty lithology aboveC property HeatProductionRate ProbabilityDistributionFunction type Normal mean 0 000001 stddev 0 0 LithologyProperty lithology ZtoC property HeatProductionRate ProbabilityDistributionFunction type Normal mean 0 000001 stddev 0 0 LithologyProperty lithology basement property HeatProductionRate ProbabilityDistributionFunction type Normal mean 0 000002 stddev 0 0 LithologyProperty lithology BLS property HeatProductionRate ProbabilityDistributionFunction type Normal mean 0 000011 stddev 0 0000015 vary LithologyProperty lithology granites1 property HeatProductionRate ProbabilityDistributionFunction type Normal mean 0 000008 stddev 0 0000035 vary MaxResidualTemperature 0 0001 NumberOfIterations 10000 In this example the embedded ForwardModelTemperatureForCreateCaseFromVoxet task has be
219. ty does not allow the inversion process a proper chance to discriminate 3D GeoModeller uses the principles of statistical sampling to drive the inversion processes You can think of this as a Monte Carlo simulation Metropolis 1949 The algorithm used has evolved quite a bit from this and concepts of topology retaining coherent volumes and shapes chaos theory all have a place Perhaps the most influential prior work is the paper by Mosegaard K and Tarantola A 1995 As in keeping with the original 3D geological modeling philosophy any observed fact can and should be held as the truth during the inversion processes Examples of this could include an observed horizon picked from a seismic section or the location of a certain occurrence of a geological unit at depth as seen in a borehole Currently inversion in 3D GeoModeller takes a snap shot of the starting 3D geological model into a voxet realization All subsequent work is then done on the voxet model without any back reference to the original facts embodied in the 3D Geological model As a consequence of this faults are not formally honored during inversion Technology Advances The size of a simulation that can be run has also gone up a lot as the software moves to the new clusters and cloud computing environments as well as being fully 64 bit address space enabled If you have access to 96 Gigabytes of main memory the tools will use this to give you accelerated capacity
220. ty models from a nominated iteration run and case Property_Optimization Property_Parameter_Sweep MakeSummaryStats Create a voxel file containing summary statistical parameters for a defined iteration range from a nominated run and case MakeSuperSummaryStats Create a voxel file containing summary statistical parameters for a defined iteration range from a nominated run and case MakeHistogram Calculate a property histogram for a nominated property iteration run and case MakeSectionImage Generate an image backdrop for a mapping module section for a nominated attribute from a voxel file derived from an iteration run and case MakeAllSectionImages MakeSurfaceShells Create a triangulated surface for a nominated attribute based on a voxel file saved from a specific iteration run and case MakeEvolutionMovie Create a movie showing the evolution of a voxet property during a run for a specified section MakeMovie Make an AVI movie from a list of JPG files Functions that are redesigned or positioned in new tools some not released at v2012 Contents Help Top DumpVoxet List the contents of a voxet with a single property to the command window 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 162 Conients Help Top lt 4 Back gt MakeDerivedVoxet Create a voxet using other voxets as inputs MakeSectionMovie Create a movie showing a voxet proper
221. ty on a series of parallel evenly spaced sections ForwardModelFromRunState Calculate the response for a specified iteration of a run SaveReferences Save the response functions for a case now part of Property Optimization 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt Contents Help Top
222. ty to run Heat simulations based upon your 3D geology model You need to specify enough boundary conditions to constrain the situation so that viable calculations can be made A seperate theory paper is distributed to explain all the equations physical constants and the possible variations Setting boundary conditions for top base and sides together with the possibility of holding an observed iso therm constant at an horizon that has a known conditon are the possible scenarios on offer The heat diffusion equation used has provision for the main potential field term the heat sources term is restricted to radiogenic sources and the advection term is limited to vertical flow Heat production from radiogenic sources is the geology source considered most important to accommodate here You access this via the properties Physical properties of geo 3P Physical properties of jc wysical pr Thermal radvection i ravity Magnetic Thermal advection Seismic SS Aea Thermal Conductivity W m K Heat Production Rate W m Formation Heat Capacity 3 ko Porosity Fluid Velocity m s Log normal 2 0 1 100 Log normal 1e 006 1e 007 100 Bb Cover Log normal 1e 007 0 100 Log normal 1e 007 0 100 Normai 0 0 100 0 0 ELSE Log normal 3 0 1 100 Log normal 1e 006 1e 007 100 a IEE Log normal 1e 007 0 100 Log normal 1e 007 0 100 INormal 0 0
223. ue where lt none gt no weighting applied LocalAbundance default localAbundance gives rise to probBack values equal to the number of voxels in the face neighborhood equal to the old lithology divided by 6 and probForward values equal to the number of voxels in the face neighborhood equal to the new lithology divided by 6 For example Commonality VolumeTest SetWeights LocalAbundance Recommended Commonality Settings Geological bodies that you have modeled in your reference model can be constrained to change using this commonality constraint via a probability distribution function e We recommend that this be Exponential This implies you have good confidence in the reference model You can define this confidence by the first parameter in the Weibull PDF by using the graph of Figure 17 Example Weibull 0 1 1 0 Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 116 Contents Help Top lt 4 Back gt Geology Tests ShapeRatio and VolumeRatio Tests The definitions appropriate here are lt Shape is the square root of surface area divided by the cube root of volume to minimize any scale dependence ShapeRatio is the Shape of the formation in the proposal divided by the Shape of the formation in the ReferenceModel Shape of a sphere 2 2 No scale dependency Shape of a cylinder
224. ull mean 0 001 stddev 1 LithologyProperty lithology SedMiddle property Commonality ProbabilityDistributionFunction type Weibull mean 0 001 stddev 1 LithologyProperty lithology SedLower property Commonality ProbabilityDistributionFunction type Weibull mean 0 001 stddev 1 LithologyProperty lithology Basement property Commonality ProbabilityDistributionFunction type Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd lt 4 Back gt GeoModeller User Manual 71 Contents Help Top 4 Back gt Weibull mean 0 001 stddev 1 LithologyProperty lithology Mantle property Commonality ProbabilityDistributionFunction type Weibull mean 0 001 stddev 1 Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 72 Contents Help Top lt 4 Back gt For Property CommonalityVolume Syntax Formation CommonalityVolume lt StatisticalLaw gt where lt StatisticalLaw gt lt Normal LogNormal Poisson Equal EqualPlus EqualMinus Weibull Rayleigh gt Associated parameters PercentageOfCommonalityVolume Units for CommonalityVolume CommonalityVolume central values for example mean for a Normal distribution and spread parameters for example standard deviation for a Normal Distribution are expressed as a percentage Examples SetLaw type
225. umber of iterations has been processed The geophysical grids for the final model are reported as a set of final grids in ERMapper format Note that these are not the inversion result but simply the computed geophysical response of one model the last model The inversion result is an assemblage of many alternate accepted 3D geology models that can be derived from the starting voxel model together with the set of progressive changes to that model recorded in the modifications txt file The master command to run a full geophysical inversion once all the required options have been set in the process control inversion XML file is for example See Appendix 2 Programmer notes on voxel coordinates and indices and Appendix 3 Sample of Populated Inversion Case XML file generated directly from the schema for an actual real process description xml file With v2012 most of the times you are working interactively and you run a geophysical simulation the results when available get added to the standard Explorer Tree under MeshGrid So first verify that the final voxet after the run is finished can be found in the Case Run MeshGrid directory if you need to check and the Project Exporer tree view does not immediately show the new work You can also try a Pull Right mouse click on the MeshGrid icon in the tree view The standard colour stretching histogram Stats and visualization capablites allow you to immediately access these
226. umes indicate areas of greater changeability of lithology such that the threshold was not met Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Ltd 4 Back gt GeoModeller User Manual 136 Contents Help Top lt 4 Back gt Property 6 and onwards The probability for Unit 0 1 2 3 4 correspond to the geological units as defined in the pile and linked to a number in the inversion xml file For the above the following index definitions were retrieved from the inversions xml file For example Formation Sub_moho Index 1 Formation Lwr_crust Index 2 e Formation Jur_basement Index 3 Formation Tert_sediments Index 4 e Formation Mio_basalt Index 5 e Formation Dummy Index 6 Index 0 is not defined it is the space above topography MakeSectionlmage The MakeSectionImage command produces an image of user specified Field such as Lithology Density on some specified Section through the 3D model The output is written both as standard JPEG jpg image files and also in the ERMapper grid file format ers The specified Section must exist in the 3D GeoModeller Project The command is used to present data or results from any 3D project voxet produced by 3D GeoModeller inversion commands such as e The Case voxet A SuperSummaryStats voxet e The initial and final voxets of an inversion Run Any specifically derived geology v
227. use the default density for all geology formations is actually the Reference Density and the Above Topography region is also assigned that same default value If doing a joint gravity and magnetic inversion the default values for magnetic susceptibility and remanence are zero and so need to be specifically set A finer resolution of the modelling of terrain effects can now be done compared to earlier vesions of the algorithm The new parameter is Vertical Sampling Interval for the spatial case This defaults to the chosen Z cell size If you make it smaller than the normal default it takes a lot longer to do the spatial calculation and beware of exhausting the 32 bit memory as you attempt this On the other hand the FFT methods are better able to cope with finer resolution discretization including in this vertical direction so we recommend you simply try a finer resolution vertically for all cells The protobuf parameter to set is part of the MeasuredGrid parameter set Here is the formal specification of the observed geophysical grid object in the protobuf language message MeasuredGrid_GMT required ctm GeophysicsSignalType type 1 required double mean_elevation 2 optional ComputeSurfaceStyle compute_surface_style 3 default ConstantElevation optional double compute_surface_z_sampling 4 optional string compute_surface_grid 5 optional double precision 6 default 0 1 optional bool Match_Trend
228. used This voxet naturally defines the computed model extents the set of lithologies to be used and their distribution in 3D space The physical properties distributions for each of the lithologies in the voxet model The reference density Gravity responses are computed using density contrasts for each lithology relative to this specified reference density The ambient magnetic field of the Earth field strength inclination and declination The geophysical parameters to be computed Gravimetry Gee Gen Ged Gnn Gnd Gdd Magnetism Me Mn Md Mee Men Med Mnn Mnd Mdd etc e The elevation at which the geophysical response is to be computed The grid geographic details the grid extent grid cell size and grid cell position Specify these with the NewCase NewCase and CaseControl CaseControl commands A Curiosity To set up a Case existing geophysical grids are used see Geophysical Grids Vertical Considerations Acquisition Elevation and Gravity Dataset and Topography Considerations Naturally the field data grids must exist when one is contemplating an inversion task but what if one simply wants to generate a forward model geophysical response and there is no existing geophysical grid Solution Use any grid software to generate one or more dummy grids These grids must have the correct geographical parameters the grid extent grid cell size and grid cell position since the X Y paramet
229. w manages the response above terrain Forward Model Parameters Set parameters for field 1 of 1 Gz Observed Grid Specify an Observed Grid From External Resource Calculation Surface Constant elevation Drape gt Terrain clearance 0 Drape gt Load from dataset m ee es ee Voxet Properties Page Either spatial or Fourier method can be chosen See the later section for a full explanation of the strengths and weaknesses of each approach Each has special requirements for padding and memory management on both 32 64 and multi CPU environments The default is to use your full project extent to create a forward model but as you can see there is provision for subsetting your project Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 23 Contents Help Top lt 4 Back gt Contents Help Top Voxet Properties Set voxet resolution and processing options Voxet extents and resolution Xmin 100000 Xmax 110000 dx 500 nX 20 Resetextents _ Ymin 2000000 Ymax 2010000 dY 500 nY 2 Zmin 8000 Zmax 2000 dZ 500 nZ 20 Processing Options Spatial Vertical sampling interval 500 Interpolate between levels Memory requirements 1MB Run Property Optimisation Variable Z 3D FFT Expansion Method Mirror Expand horizontally by 100 et Expand vertically by 400 Memory requirements 0 MB i
230. xels across the JPEG image Section lithology snapshots see further note lt MaxRows gt the maximum number of pixels down the JPEG image Section lithology snapshots see further note e lt VerticalExaggeration gt typically 1 is the Section Vertical Exaggeration to be used see further note below e lt FramesPerSecond gt defines the movie speed in terms of the number of Section snapshot frames to display per second lt QualityPercentage gt say 80 to 100 defines the quality of the JPEG snapshots images 100 uses no JPEG compression e lt IterationIncrement gt is the increment of iterations between each Section snapshot image suggest 1 500 of total iterations lt ColourScheme gt is one of lt LithologyColours Colours Greyscale gt e lt EvolutionField gt is one of lt Lithology Density Susceptibility RemanenceEast RemanenceNorth RemanenceDown gt e lt Section gt is the name of an existing Section in the 3D GeoModeller Project lt OutputFilename gt the filename of the output avi movie and optionally the relative or absolute path of the output directory which must exist and where e lt RunIntervalList N gt lt Run gt lt StartIteration gt lt EndIteration gt where lt Run gt an alphanumeric string or identifier that identifies the inversion Run Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModel
231. xet zCellSize 2 where nZ Number of horizontal sheets of voxels in the geology Voxet such that ElevationMaxVoxet nZ x zCellSize lt ElevationMinVoxet and ElevationMaxVoxet nZ 1 x zCellSize lt ElevationMinVoxet Thus the Z division of the 3D GeoModeller Project into voxels is calculated from the specified top ElevationMaxVoxet then working downwards until the lower limit is reached That lower limit does not need to be specified exactly The NewCase command e Creates a lt Case gt subdirectory in the project directory Copies the 3D GeoModeller Project to that directory with Project name lt Case gt Copies the input field observed geophysical grids to that directory For an inversion run we create the inversions xml file this file is used to record all parameter settings for the Case and for subsequent inversion Runs performed for that Case e Creates the lt Case gt vo file a GoCad voxet with the Lithology as a field Lithology is coded as integers 0 the above topography region and 1 2 3 are the indices for the geological formations which are listed in the corresponding order in the inversions xml file The NewCase command brings together a range of geology and geophysical datasets to create the Case You need to ensure that the datasets are compatible with each other and compatible with the way in which 3D GeoModeller geophysics tools operate The following Notes add further important de
232. y 1 is the Section Vertical Exaggeration to be used see further note below lt FramesPerSecond gt defines the movie speed in terms of the number of Section frames to display per second lt QualityPercentage gt say 80 to 100 defines the quality of the JPEG snapshots images 100 uses no JPEG compression lt NoFramesAlongSweep gt the number of discrete Sections movie frames to be generated between the Start and End points of the movie sweep line lt MaxSectionWidth gt the maximum length of Section either side of the defined central sweep line that controls the Sections The widest possible Section would actually be twice this specified width Actual Section widths may also be limited by the edge of the 3D Project GetField lt DerivedVoxet gt lt FieldWithinDerivedVoxet gt extracts data for a specified Field from a specified Voxet There must be no spaces within the Q lt DerivedVoxet gt any 3D project voxet which is derived from the 3D GeoModeller Project lt FieldWithinDerivedVoxet gt is a Keyword as used in the voxet header file such as Lithology MostProbable MostProbableThresholded MeanDensity StdDevDensity Probablity0 Probablity1 lt ColourScheme gt is one of lt LithologyColours Colours Greyscale gt lt ScaleOption gt lt LinearOrLog gt lt minClip gt lt maxClip gt where e lt LinearOrLog gt 0 for Linear and 1 for Log lt minClip gt
233. y once every 5000 iterations Filename lt CaseID gt _ lt Run gt misfits SetOutputCommonality SetOutputCommonality is simply an output option By default it is off If you SetOutputCommonality true then the Commonality misfit values will be written out to a misfits file at every iterations Filename lt CaseID gt _ lt Run gt _commonality rpt This file has columns of iteration number proposal number MisfitCommonality1 MisfitCommonality2 MisfitCommonalityN and CommonalityRejectionFlag MisfitCommonalityN refers to the Misfit Commonality value for the formation with index N CommonalityRejectionFlag is a flag to indicate whether the iteration involved a Commonality rejection 1 or otherwise 0 SetOutputTrendGrids SetOutputTrendGrids is simply an output option By default it is false This means that trend grids are not saved as they are calculated If you set SetOutputTrendGrids true then trend grids are saved This is useful when the trend matching rate has been set in the Case AllowPropertyChangeOnFixedCell Note that 3D GeoModeller SetFixedCells is specifically setting fixed the lithology values for those cells By default even for these fixed cells the property values will be modified during the inversion The default for AllowPropertyChangeOnFixedCell is 1 yes allow change To fix both the physical properties as well as the lithologies of the fixed cells use this RunControl command with AllowPropertyC
234. y voxet such that the inversion process cannot change the lithology of those voxels For example voxels at the surface or intersected by drillholes could be considered to have known geology and therefore should not change during inversion Misc V Fix cell lithologies with Surface Initial observed Unspecified Observed Inferred Interpreted ModelConstructor Select all De select all Properties Fix lithology frontier Canetrainte The above image shows the third page of the Inversion wizard and the user is setting cells that conatin a geology observation with an Observed classification There are several variants of this function providing alternative means of specifying which voxels should have fixed lithology In batch the command can be executed more than once to achieve a required combination of fixed lithology voxels The outcome of successive SetFixedCells commands is cumulative and are stored by updating the Modifiable field of a special voxet called lt Case gt _ lt Run gt _modifiable vo There is also one special variant of the command to clear all fixed lithology voxels resetting all voxels to have modifiable lithology The SetFixedCells command is currently applied to an inversion Run You should execute the same SetFixedCells commands for all Runs of a given Case We would recommend that a new Case be created when experimenting with different combinations of fixed lithology voxel
235. yProperty lithology SedLower property Movable fixed false Contents Help Top 2013 BRGM amp Desmond Fitzgerald amp Associates Pty Lid 4 Back gt GeoModeller User Manual 67 Contents Help Top lt 4 Back gt LithologyProperty lithology Basement property Movable fixed false LithologyProperty lithology Mantle property Movable fixed false For Property Index This is similar in concept to the Moveable fixed discussion above The aim of this batch option is to allow you to nominate a integer unit number in a voxet for special consideration Syntax Index lt integer gt where lt integer gt the voxel value assigned to this formation within the voxet This is useful when setting the initial lithology from a voxet created by some third party software Examples SetLaw LithologyProperty lithology Air index 6 For Property Commonality Syntax Formation Commonality lt StatisticalLaw gt where lt Statisticallaw gt lt Weibull Rayleigh gt e Associated parameters for Weibull are and x whilst the associated parameter for Rayleigh is beta Examples Formation Commonality Rayleigh beta Formation Commonality Weibull A x Pitfield_Volcanics Commonality Rayleigh 0 20 Ercildoun_Granite Commonality Rayleigh 0 20 A Weibull distribution has Weibull A x where gt 0 is the scale parameter and x gt 0 is the shape parameter It is defined f

Forward modelling and inversion with 3D GeoModeller

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