A Matlab GUI for use with ISOLA Fortran codes User's Guide by
Contents
1. employed crustal model is not appropriate at some station as regards the arrival time Running the Fortran codes without Matlab ISOLA can be used also without the Matlab GUI In case like that the user should study the readme files that are provided with the Fortran files distribution at Attp 2 For compactness of Us Guide all the readme files of the ISOLA Fortran version are copied below Users of the Matlab GUI can skip this part Instruction Go trough directories and follow readme files there Start in DATA continue with SOURSTAT GREEN INVERT POLARITY and optionally also SYNT Use sample input and output data files to learn the package The sample files do not contain exe files because of their length and because users should be able to compile all for codes themselves In case of problems ask the author to send the exe files The example is highly simplified to allow quick test run For more details see the application referenced below Acknowledgments Special thanks go to Petra Adamova for extensive testing of ISOLA GUI The following m files are part of other programs that we found useful and added to the GUI e rsac m Ih m by Michael Thorne e readgcffile m by M McGowan Guralp Systems Ltd e Bandpass m Coral distribution In the Fortran part several subroutines were used written by other authors M Bouchon O Coutant J Sileny J Jansky and O Novotny J A Snoke P Reasenber2. is sufficient Finally the user has the option to plot the MT inversion results along with selected polarities Fig 17 in order to check validity of the inversion A few files need to be updated for this option Namely the station dat file has to be manually edited to assign the observed polarities per stations This can be done within the GUI by_pressing Input Polarities after which the station dat file opens in an editor The other two files that need to be created are onemech dat and moremech dat that the user has to create in the POLARITY folder The onemech dat contains data to be shown in red e g the solution from ISOLA while moremech dat can include for comparison several other solutions e g those from several agencies The polarity plotting is still under heavy development Present version needs some knowledge of the ISOLA Fortran manual In particular the mentioned files should share the same format as that of the output file INV2 DAT Figure 17 Plot of polarities with inversion results Moremech dat example a_space sepated text file only columns 4 5 6 4 6 66 185761E 18 L t E Tle 13 19 131 251 61 d 32 88 9 7718E 00 1 3 96 560486E 17 201 50 144 316 63 46 76 83 175 39 68 4 8426E 00 Utilities and Il Besides the inversion related tools a number of options is provided for assisting the user in converting his binary data to ISOLA ascii format and inspecting the data quality Tools are
3. available for importing data in two formats SAC and GCF Guralp Compressed Format The tools are quite easy to handle just read the files component by component and then save the file Fig 18 If the three components at a station don t share the same starting time or don t have the same length options for their trimming are provided Cormar et Tee re Note F m ihodd have the Lame amping ais Figure 18 The GCF file import form The tools for importing data are based on free Matlab routines from the Web see acknowledgment part of the manual The user can use them as an example to easily add his preferred format conversion to the present GUI After converting the data to ISOLA format the user has the option to inspect the data quality either using the Inspect Data tool or the Try Filters tool Data can be filtered in various frequency bands in order to define the proper band for inversion i e the band with a good signal to noise ratio Data can be also inspected as the displacement It is extremely important to inspect the displacement without filtration and instrument correction since it allows detection of various disturbances that are often A dden in the velocity records and or in the displacement band passed records Zahradnik and Plesinger 2005 Finally the data can be shifted using the Shift data option This option may be used with great caution when for example we have an indication that the
4. example his knowledge about the first motion polarities geologically deduced fault dip various assumptions about rupture propagation etc The 2D correlation may also help in identifying poor resolution of some parameters for example the down dip source position Narrow band pass inversions around period T can often provide two correlation maxima in time t and t T 2 characterized by rake and rake 180 respectively This is just the case where even a single guaranteed first motion polarity may help to decide between proper time t or t T 2 The code works iteratively A point source contribution is called subevent Using data code searches for subevent 1 Once subevent 1 is found its contribution is subtracted from the data to get the so called residual data In the next step the residual data are processed in the same way as the original data during the first step Subevent 2 is found etc Original data minus the last residual seismogram provide the resulting synthetic seismogram Optionally the search of spatial and temporal distribution of subevents can be performed with fixed 100 DC moment tensor The user prescribes the known or assumed strike dip and rake and these values are kept fixed for all subevents It can be recommended when the unconstrained moment tensors vary chaotically from one subevent to the other When the solution is represented by several subevents of different focal mechanism the resulting scalar
5. of the beach balls The plot formally includes all the calculated subevents Lot of care is needed to find out which of them are physically justified This complicated physical problem is not solved here in the manual See for example Zahradnik et al 2005 MOMENT TENSOR SOLUTION rial sour z i6 Rer Mtt Mpp GH Bapth Kit 74 173 25 654 99 828 Source time shift 6 66 Moment N m 1 809e 017 Mer Meg Mtp Mw 5 6 82 240 132 114 21 304 bce 865 Exponent Mm 15 CLYD 15 10 7704 amp 77 04 Variance red Strike Dip Rake iso 76 H Strike Dip Rake 17 19 135 20 9 21 Figure 13 The Single source summary plot Condition number Irma max eigenvalue ratio 0 278977 DC 100 Variance Reduction CEKEERK Source no Figure 14 The Correlation vs Source number plot By the source number we mean the sequential number of the trial source position The values above the beach balls give the time shift plsources Map Border Deg Legend length km Legend shift Source symbol size Move source text dx dy Source Text size Figure 16 Plot of the multiple source inversion results Full numerical results of the inversion are available in the files invl dat inv2 dat inv2c dat inv3 dat inv4 dat located in the folder INVERT For a detailed explanation the readme files of the ISOLA Fortran guide should be consulted see below Most often simpler output that provided in the Plotting form
6. very near to that of the unconstrained deviatoric MT inversion Thus the most recommended inversion mode is deviatoric inversion VOL 0 in which however the resulting DC is considered with great caution It is assumed in the above explanation that the source position and time are known This code allows their optimization through a grid search over set of trial source positions and time shifts pre defined by the user The search seeks the trial source position and time for which the residual error of the least square method is minimized It is equivalent to maximize correlation between the observed and synthetic seismograms The concept of optimizing position and time is applicable to each point element the so called subevent of the generally more complex source model If the whole earthquake is represented in the low frequency range by a single source the optimum solution provided by the grid search corresponds to the centro d the centroid position centroid time and the centroid MT User can check the correlation values as a 2D function of the trial source position and time The code has an interactive part in which user can use automatic search of the optimum correlation or can make his preferred choice The preferred choice may be the source position or time with a somewhat lower correlation close to formal maximum in which however some other conditions constraints are better satisfied In this way user can apply for
7. A Matlab GUI for use with ISOLA Fortran codes User s Guide by Efthimios Sokos 1 and Jiri Zahradnik 2 1 University of Patras Seismological Laboratory 2 Charles University in Prague Faculty of Mathematics and Physics esokos upatras gr jz karel troja mff cuni cz Ver 2 5 June 2006 Contents GU PUR POS A E E A A aeneceevcunucancosevaeusenweassenseate 3 REQUIREMENTS cccccccsecceeccceecceseceeeeeeeeeueeeeeeeneeenueeeeseeneeenaeeceeseeeeeceeeeaes 3 INSTALLATION sek KEEN K ENKE KEN ceases KEEN EEN RENE KENNEN KEREN KEN KENNEN KEREN A ol te lgl NN 4 RUNNING THE GU ccc cc cccecceeccseseceesceeseneeecesseesseceeeneeseeeseceeeeusseeeseneees 10 Crustal M del iinet eea ta a a ee re eeaeee aae 11 Event NEE 13 Station SOIC ON s is eer 14 Raw Data Preparation iicccsccscisscscisnsesscssssisssdcsvevscsesscctssonsessesessscscscvonsessnstscsssassossesnsscecsdesesssosessacsceee 15 Trial Source Dehnttient ere SOEN Ehe ee eer 18 Green Function Computation cscssssssscscscssssssssssscecscssssssssscacecsassssssscacaceasasecsscecasensases 20 MaN Lo a EREE EET EEA NA E AR EE O EEEE N EEA 22 aloan ao DE 25 Utilities Land UN EE 31 RUNNING THE FORTRAN CODES WITHOUT MATLAB 0 cc0cccseee 33 ed e UR RE E A 33 GUI Purpose The ISOLA GUI has been created using the Matlab GUIDE tool Its purpose is to help the user of ISOLA FORTRAN part with data preprocessing Green function preparation waveform inversi
8. a bier wu Aa 5 al Te Dh ay malah ard ad to Matlab path E Bn K P 2 Wy tee ce Gi te TD e gl H keng pr pate rr eg E Se wE SE E Figure 4 The Station Selection form Options in this form are simple the user should press Make Map Select stations in order to select his previously prepared text file containing the geographical coordinates of his network The name and location of the file is arbitrary the user will be guided to browse The file should be an ascii file with three columns Station Name Latitude Longitude separated by spaces The Station Name should have 3 characters If it is longer a warning is issued and the station name is reduced to the first three characters Pressing Make Map Select stations and assuming that M_MAP is properly installed a map of the station distribution is created and the user can select the stations he wants to include in the inversion Selection of the stations is done using the left mouse button the last station should be picked using the right mouse button After pressing the right mouse button a warning window comes up with the total number of the selected stations Later during the inversion stage if necessary the user can again deselect some stations Le to remove them from the inversion process but once the station was selected the corresponding seismograms must be provided After finishing the selection of the stations the user should just press Exit on
9. creates the proper filename for the corrected resampled data which for station LTK would be LTKraw dat This filename must not be changed by the user Trial Source Definition The final data that the user should prepare is the trial source location and this is done by pressing the Seismic Source Definition button in the ISOLA main form The user has to select Single Source or Multiple Source definition In the case of single source we can vary the depth only thus the options in the form are Starting depth Depth step and No of Sources the explanation of which is given in Fig 6 In this case all the trial positions are below the epicenter By pressing Exit the program writes the appropriate files in GREEN and GMTFILES folders These files are src det files in GREEN and sources gmt in GMTFILES The sources gmt file is formatted for GMT psxy plotting It is assumed that the Single Source option will be always used to retrieve at each trial depth just a single subevent that one which predominates in the low frequency inversion The grid search over the depth then serves to provide the optimum source position characterized by the best fit between the waveform data and synthetics Thus we get a first approximation of the centroid By the first approximation we mean that opposed to assumption of this option the centroid is not necessarily below the epicenter sourcesel Select Single or Multiple Source Starting Dep
10. cts a data file When the file is read the sampling frequency is displayed in red at the top of the form Fig 5 side by side with the resampling frequency of the data in blue The resampling is made automatically based on specific methodical requirements and the data input from the previous steps After data loading the Cut and Instrument correction buttons are enabled If not all of the data is needed using the Cut button the last part of it can be deleted By pressing the Inst Correction button the program searches in PZFILES folder for the appropriate pole and zero file and then performs the instrument correction During this operation a filter can be applied Butterworth 2 order zero phase along with the DC and trend removal all using the built in Matlab functions The baseline option is an alternative of the DC removal in which the baseline is determined from the beginning of the seismogram only Next step is the time alignment of the seismogram i e irrespectively of its Start Time since now it will begin at the earthquake Origin Time this is done by pressing the Origin Align button which becomes active after the instrument correction Finally the user should press the Save Data button in order to save the files in INVERT folder The files are saved as text files 4 columns Time in sec NS EW Z in m sec one per a station always containing just 8192 points of the appropriately resampled data The GUI automatically
11. ents Seconds Magnitude Date Location agency Raw data start time Data Options NS Time Length sec This is the part of data that will be used for the inversion starting at origin time Figure 3 The Event Info form In this form the user provides information that will be used in all the subsequent steps of the inversion like the event Lat Lon Depth Magnitude Date the last two are included just for information Origin Time of the event Start Time of the data file seismograms Sampling Frequency and finally the Time Length of the data that will be used for the inversion The time length should satisfy some specific conditions For user s convenience there are 3 predefined time length intervals that should cover most applications at local and regional distances After pressing the update button the GUI writes or updates the appropriate files e g event isl rawinfo isl duration isl those are ISOLA isl related text files that hold the above information and are stored in ISOLA folder Next step is the selection of the stations that will be used for the inversion Fig 4 Station Selection s n Selection DINA AAS SS pt 7 Ka EH KH el age AN PNS i Hit CH e Fa ba e Va gien he gen hi ba a lad We j hd Ze E seth Reeg Caen PANE LAT Lt RA UX tose soused ro header e pe KA e Le Ea dE dh a a rank t M MEF a needed heme reg fram d he w KR une Hay eren cy ube cain
12. escribes the code options It cannot describe all possible strategies how to use the code For example the user may use the Multiple Source option in the beginning of his study to find the centroid the first application which might need trial positions relatively far from the hypocenter and with a relatively large grid spacing Then he may wish to repeat the same procedure with finer grid spacing to find the exact position of the centroid Finally he can try the application of the second type i e to resolve several subevents The latter may often fail due to lacking data or simply because the earthquake has no clear complexity then his result remains to be just the precise centroid solution with no additional details This discussion explains why it is nearly impossible to give an always working hint of where and how densely the trial source positions should be designed Erost par armatori D EE iw in m Mee Pypocentet poubon ego Am Res Pee Drei et pr Cat hd He ot Cement te Rent he Geer geng Sanne him wne Pat Longa Bel o He af twee ntomg Se Fei diye Spean weng rg fre Teen Wha Gent o Shiftto North Iretesemer ae TE soere zember peter engen at Dy same combes Shift to East Hypocenter Figure 7 The Multiple Source definition form Green Function Computation After finishing with the trial source definition the inversion can start and the first step is
13. g and D Oppenheimer Codes from Fortran Numerical Recipes were also used This work was supported by the EC project 004043 3HAZ Corinth and by the Charles University in Prague grant GAUK 279 2006 B GEO MFF
14. ication of weights Wote that the larger the number in allstat dat the lower Is the weight See also the Method chapter to learn more about the weights and correlation Example of the allstat dat file GUR 1 6 057019e 005 2 130505e 004 3 082369e 004 LTK 1 6 179501e 005 2 366762e 004 2 285469e 004 DID 1 1 139388e 004 1 451932e 004 1 765126e 004 PYL 1 1 145303e 004 1 020548e 004 1 030644e 004 Figure 10 Example of the inversion run P fe C2 Ceres mg Corte Meade reg Si Pap A ac ES LA eA AA Ate A IMM LILIA AAA AAA AAA AeA A AEEEAETITTTY OOM I IAA AAA A A hb db ITT MAA AA EE EE AAA AAA SOM MNAAM EEN E AA AAA AA PESCO EK EA AAA AAA A ZP AAA MAM Ae baa at EE E ET EE o 27 3 S o 2 gt d FEEF Ulery re rrr rrr Fees he AA AAT EEEE EE EEFEFTEEeCnhRAA4A44lAl ASS ew we ehh tT EEEE Time sec Figure 11 Example of the correlation plot 30 70 000 cil Plotting The inversion code isola exe creates a number of output files that can be plotted after the inversion run This is done by pressing Plot Results button of the main ISOLA form The plotres m is called and produces the form of Fig 12 There are options for plotting Synthetic versus Real data the MT results as well as for comparing the solution with first motion polarities The MT moment tensor plotting is done using GMT and the user has the option for a single source summary plot Fig 13 a plot of Correlation versus Source number a
15. in rad sec Comment 3 Number of zeroes 0 0 0 0 Zero 0 0 0 0 Zero 51 5 0 0 Zero poles Re and Im in rad sec Comment 5 Number of Poles 272 218 Pole 272 218 Pole 56 5 0 Pole 0 1111 0 1111 Pole 0 1111 0 1111 Pole It is strictly required that the file describes the instrument transfer function for input ve ocity The filename must be a combination of the Station Name and the_ BH pz string for example for the station named LTK and the EW component it must be LTKBHE pz thus three pole and zero files per station are needed The location of the pz files is not arbitrary the user must place them in the PZFILES folder Caution must be devoted to the appropriate units ISOLA needs the poles and zeros in rad sec and the constant of the transfer function AO guaranteeing that the plateau of the amplitude response equals to 1 should be consistent with that In case that the user has the zeros and poles in Hz they all must NP NZ be multiplied by 2x and correspondingly AO must be multiplied by 27 where NP and NZ is the number of the poles and zeros respectively Sampling Frequency 50 33 Re Sampling Frequency Current dala view Raw data init Comection Pei Begeegeg Taper kW OC wgl k Tiondismovs M Baseline Lowasa Wel Hehad Dr mm KA Ce S Time vee Figure 5 The Data Preparation form Pressing Load Ascii file a standard open file dialog appears and the user sele
16. is an internal property of the least square minimization of d s during the corresponding matrix operations G GT G etc that we automatically get the value of where cis the correlation between d and s without numerically calculating the correlation integral Speaking more precisely we get sqrt c abs c i e not the correlation c but only its absolute value Anyway hereafter we simply say only correlation At the same time it can be shown that nc 1 d s d varred When we calculate already the second subevent s2 the least square method minimizes r s2 where r is the residual seismogram defined as difference between the original data and the first subevent del Therefore from this least square run we get automatically and we report on the code output the absolute value of the correlation between r and s2 At the same time after adding the second subevent the code calculates varred using d and S S1 s2 i e varred 1 d s1 s2 d Obviously the varred value reported after the second subevent is not the same as the squared correlation between r and s2 Moreover this varred is also not the same as the squared correlation between d and s sl1 s2 because we did not find the synthetic s s1 s2 by a single least square minimization of d s1 s2 When non unit weights are used and or some stations are deselected from a particular inversion run the relation between correlation and variance red
17. moment cannot be obtained as the sum of the subevent scalar moments That is why we also provide an output file where subsequently the subevent contributions are summed up as tensors and the scalar moment of the resulting cumulative tensor is shown Denoting data as d and synthetics as s the fit between them is measured by the so called variance reduction varred 1 d s d where denotes the L2 norm e g d suma d The norm is calculated as a single number summing up over all time series all components and all stations The optimum value of varred is 1 Wrong synthetics may give even varred lt 0 no physical meaning The variance reduction is determined repeatedly when building up the synthetics i e after adding every subevent In other words when s1 si are synthetics corresponding to individual subevents then first we calculate varred from d and s s1 then from d and s s1 s2 etc As such varred is a measure of the convergence of the iterative deconvolution process Slow increase of varred with adding subevents indicates that additional subevents do not further improve the fit At this point it is useful to clarify how the variance reduction relates with the correlation The relation is simple when all stations and all components are used and all weights equal 1 and when we calculate only the first subevent Take the observed seismogram as data d and the first subevent as synthetics s sl1 It
18. nd DC Fig 14 or multiple source results plot in map view pressing Plot Sources In all the plots except the one in the single source summary the fault plane solutions are displayed by beach balls without showing the non DC component because as explained above the non DC part is usually unstable Note that the single source plotting option applies also for the inversion which resulted in several subevents The code prompts the user to specify the subevent he wishes to plot in Fig 13 and Fig 14 The variance reduction given in the Single Source plot in Fig 13 then refers to the situation after adding the chosen subevent for example when plotting subevent 2 the varred value applies for the fit between data and the synthetics composed of subevent 1 and subevent 2 The fit is calculated only from stations used in the inversion the deselected stations are not considered Inversion Results Plotting Waveforms Inversion Results Focal Mechanisms Focal Mechanisms Select Stations to plot Chack Invi Pict moment reno TK PYL W Add map I Wile ge Figure 12 The Plotting form Pressing the Plot Sources button the plsource m opens This creates the form of Fig 15 The user has a lot of options in order to create a map with the results Fig 16 Most of the options are self explanatory but some knowledge of GMT is needed The most critical are the Beach ball shift and Beach ball X shift to prevent overlapping
19. on and display of the results In addition to the main tools a few utilities are also present that help the user to inspect the quality of the data using filters convert to displacement etc In utilities there are also two other options that could help Backup files and Create folder structure The Backup files option saves in a user specified folder a number of files that are critical for running the inversion in this way the user can keep track of various attempts during an experiment The Create folder structure option creates the folders needed for ISOLA if these aren t present Finally the import SAC and GCF Guralp Compressed Format options help converting SAC and GCF binary files in ISOLA ascii format 4 columns of ascii data per station Le Time NS EW and Z component Requirements In order to use ISOLA GUI you need to have the following software installed e Matlab 6 5 or 7 0 the software has not been tested using other versions of Matlab e Generic Mapping Tools GMT Wessel and Smith 1991 1998 the software was tested using version 4 0 and 4 1 other versions should work also e M_Map this is a freeware Matlab based package it is used in map creation within Matlab you can download from http www2 ocgy ubc ca rich map html and you have to add it in the Matlab path e Ghostscript and GsView for Postscript files display http www cs wisc edu ghost and you have to add it in the system path Installation Ins
20. osed and 1 is the inverse of the so called system matrix GT G Eigenvalues of the system matrix GT G are calculated to understand how well posed or ill posed the inverse problem is Ratio of min max eigenvalue is reported The lower the value the worse the results are although formally the quality of the fit may be good e g variance reduction can be large Question how the individual stations contribute to the well posed inversion has no simple answer It is to be carefully analyzed case by case Optionally the weighted inversion is performed with weights prescribed by user different weights for different stations and components As a rule up weighting records with small amplitudes and down weighting large amplitudes is recommended Another strategy is to up weight stations whose seismograms appear to be the most sensitive with respect to small modifications of the problem The coefficients a are related to moment tensor Mpq where p q refer to geographic coordinates x gt 0 N y gt 0 E z gt 0 up Mxx a4 a6 Myy a5 a6 Mzz a4 a5 a6 Mxy Myx al Mxz Mzx a2 Myz Mzy a3 Moment tensor components in spherical coordinates r t theta p phi used in Harvard catalogue or in GMT are given by Mtt Mxx Mpp Myy Mrr Mzz Mtp Mxy Mrt Mxz Mrp Myz Eigenvectors of the moment tensor provide strike dip and rake Eigenvalues provide scalar moment Mo and decomposition of the moment tensor into three part
21. rsion The only correct application of this code is for subevents whose true durations are shorter than dur Figure 8 The Green function computation form Inversion The last step starts by pressing Inversion in the ISOLA main form it runs invert m that produces the following form Fig 9 Filter filter f1 2 f3 f4 flat band pass between f2 f3 cosine tapered between fl f2 and between f3 f4 A f2 D H 0 05 0 05 0 09 0 1 Info Time Length 245 76 Compute Weights No of Sources 5 No of Stations Min Time shifts sec 37 5 Max Time shifts sec Type of Inversion dt Time Search sec 280 Start 8 4 ai gt l e Deviatoric MT 34 Time Step 1 02 C DC constrained Deselect Stations C FullMT 161 End 4 83 Fixed mechanism ES fl bz Trial Time shifts Number of Subevents Plot Scale X 23 Plot Correlation diagram m 1 Plot Scale Y 15 oullge Saute Number Beachball Scale 05 C Use Distance Depth GMT Palette cool X Plot DC Font size aD V Draw Contours Use fixed interval Contour interval DI Figure 9 The Inversion form Before running the inversion the use has to select his options regarding the Filter Type of Inversion Number of Subevents to be retrieved and parameters of the Time Search temporal grid search of the subevents The same filter is automatically used for the data and
22. s double couple DC compensated linear vector dipole CLVD and voluminial VOL Possible moment tensor MT inversion modes are as follows full MT inversion all six basic focal mechanisms 1 2 6 DC CLVD VOL deviatoric MT inversion basic focal mechanisms 1 2 5 DC CLVD VOL 0 DC constrained MT inversion DC only VOL CLVD 0 known and fixed DC moment tensor only position and time is searched Opposed to strike dip rake and Mo the DC is strongly unstable It closely relates with the fact that a large deviation from pure DC has as a rule a very small effect upon the seismograms Indeed it can be demonstrated by many examples in which synthetics for say DC 50 and DC 100 cannot be distinguished by eye from each other and quantitative measure of their fit with real data is nearly identical e g variance reduction introduced below differs by 1 Therefore we can say that the DC value provided by the routine moment tensor inversion is rarely of any physical meaning The same applies for the volume percentage VOL Optionally the inversion can be constrained through the Lagrange multipliers to give a nearly 100 DC solution The non linear condition that the moment tensor must have zero valued determinant is solved iteratively It Slows down the calculation and may create problems There is no special advantage in this option because the strike dip and rake of the DC constrained solution is usually
23. synthetics Then the user may press the Compute weights button which automatically calculates weights to be applied in the inversion If not pressing this button unit weights will be used The automatic weights are inversely proportional to peak values of the individual components in the used frequency band n fact what are computed by the Compute weights function are just the peak values for the traces and latter isola exe takes the I peak value as the weight Finally pressing Run the main executable Fortran code _isola exe_ is running in the Command window Fig 10 When the code makes a pause it prompts the user to accept the automatic selection of the trial source position that of maximum correlation or to select some other user s preferred trial source position To simplify the decision the user can plot a correlation diagram using the Plot Correlation option Fig 11 GMT and Gsview is needed In this 2D diagram the correlation value and focal mechanism are plotted against the trial source position and time shift for the subevent under study Pressing the Deselect Stations button the allstat dat file opens using notepad and the user can remove a station from the inversion by editing the second column of the file 1 use the station O not use it The columns 3 4 5 contain the above mentioned peak displacement values for the NS EW Z component respectively The user can manually edit them thus making his preferred specif
24. tallation is easy just unzip the zipped distribution file in a folder This will create the necessary folders and extract the files needed for running the Matlab GUI After this operation you should get a folder structure like the following isola gmtfiles green invert pzfiles polarity A typical location would be the Matlab folder e g c matlab isola Method ISOLA is based on multiple point source representation and iterative deconvolution method similar to Kikuchi and Kanamori 1991 for teleseismic records but here the full wavefield is considered and Green s functions are calculated by the discrete wavenumber method of Bouchon 1981 Thus the method is applicable for regional and local events Instrumentally corrected band pass filtered velocity records are used The code transforms velocity into displacement inverts the displacement and provides synthetic displacement Seismogram s t is approximated by a combination of elementary seismograms elt i 1 2 6 ie s t sum a eil The elementary seismograms correspond to basic focal mechanisms as follows i strike dip rake 1 0 90 0 2 270 90 90 3 0 90 90 4 90 45 90 5 0 45 90 6 isotropic d q Seismograms 3 component from a set of stations represent the data d while the coefficients a are the parameters to be found m The linear inverse problem d G m is solved by the least square method m GT G 1 GT d where GT is G transp
25. th Single Source Multiple Source Depth step Starting depth km Depth step km No of Sources lt 19 10 Figure 6 The Single Source definition form If the user wishes to use the Multiple Source inversion a new form appears Fig 7 This inversion has three options sources along the strike of the fault sources along the dip or sources on a plane The user has to select the fault strike and dip the number of the trial sources he wants to try their spacing and the first source position After pressing the Calculate button the program writes the source files in GREEN folder and produces a map with the trial source distribution The Multiple Source option has two different applications The first one is to prepare trial positions for the grid search of the centroid inspecting usually positions in the vicinity of the optimum depth found with the Single Source inversion In this application we do design a Multiple Source stencil but make inversion in such low frequencies that just a single subevent represents the whole source The second possible application of the Multiple Source option is to design the trial source positions for inversion of the earthquake into a complex source model consisting of more than a single subevent Obviously as a rule the latter is achieved by the inversion including higher frequencies and using a denser grid of the trial positions than of the first application This manual d
26. the Station Selection form Doing this the GUI will create files like stations isl station dat source dat in GREEN folder and allstat dat in INVERT folder Raw Data Preparation Next step is the Raw Data Preparation Fig 5 maybe the most important option of the GUI since it processes the seismograms doing the instrument correction origin time alignment resampling and produces data files ready for the inversion The data i e the uncorrected seismograms must be available in 4 column text files with the strictly required column order i e Time in seconds NS EW Z in counts separated with spaces one file per station The filenames are not completely arbitrary for example for the LTK station the filename must start with the letters LTK where LTK is the station name used in the Station Selection The remaining part of the filename including the extension is already arbitrary The location of the file is also arbitrary as well as the extension and the part of the filename after the first three characters the user will be guided to browse The user should make available also the files containing the parameters that will be used for the instrument correction An example of such a pole and zero file follows A few pole and zero files for several instruments are included with the software distribution also AU Comment 133310 AO value count gt m sec Comment 3 33e 10 conversion counts to m sec zeroes Re and Im
27. to prepare the Green functions This is done by pressing Green Function Computation in the ISOLA main form The greenpre m is running Fig 8 and for simplicity the user has only one option to fill in this is the maximum frequency of the Green functions to be computed fmax Obviously no higher frequency than this one can be requested later in the inversion Pressing Run the necessary files are created in GREEN folder and the executable Fortran codes are called from Matlab gr_xyz exe and elemse exe for the Green function and elementary seismograms respectively The execution is monitored through the Command Window The user should watch the execution of the Fortran programs and press OK in the Copy files in invert folder dialog when the procedure ends After that copying starts and a message is issued when the files are copied in INVERT folder and the user can proceed to the inversion For simplicity this version of the code does not specify any particular slip rate time function It means that the assumed slip rate is that given by the Green function calculation By definition the Green function is response of the medium to the impulsive Dirac delta function source but note that we work in a limited frequency band Therefore working with the band limited delta function the actual slip rate function applied in the code has duration approximately equal to dur 1 fmax where fmax is the maximum frequency considered in the inve
28. uction gets even more complicated Running the GUI In order to run the code within the Matlab command window change directory using the cd command to the isola folder and type isola This will run the main GUI file and you should get a form like the following Fig 1 Utilities Create folder structure Backup files Event info 5 P Dishne Crustal Model Green Function Computation Sac Import Station Selection Inversion GCF Import Raw Data Preparation Utilities II Plot Results Seismic Source Definition Inspect Data Ge Try Filters Shift data Figure 1 Main form of the ISOLA Matlab GUI Crustal Model The first step in the inversion procedure is the definition of the crustal model This is done by pressing the Define Crustal Model button in the main form which will launch the form shown in Fig 2 There is a fixed option for a maximum of 15 layers in the crustal model For each layer the user should give the depth of the layer top the Vp Vs velocities in km sec density in g cm Qp Qs and optionally a title In order to allow the program to understand the last layer the user should type 999 in the last row as shown in Fig 2 There are buttons for saving the data Save in a text format file suitable for ISOLA Fortran as well as reading it back in the form Read The latter is useful for editing a previously saved model The plotting option Plot generates graphs of Vp and Vs versus depth A
29. utomatic calculation of Vs according to a specified Vp Vs value is also possible as well as the calculation of density according to formula density g cm 1 7 0 2 Vp km s Pressing Save the crustal model file that was created is saved under the GREEN and POLARITY folders Crustal model defiritian Crustal model e NEEN veier Depp Gei Vp adepc Ve hinfenc Deng ies H Op Qs U Ze 2 x E 3 Reet 4 H 5 1 D En 6 y S Lg fen ge H Er d i Figure 2 The Crustal model definition form The native format of the crustal model file in ISOLA Fortran is the following Crustal model Tomography model number of layers 8 Parameters of the layers depth of layer top km Vp km s Vs km s Rho g cm 3 Qp Qs 0 0 5 47 2 700 2 560 300 300 2 0 5 50 2 860 2 800 300 300 5 0 6 00 3 230 2 940 300 300 10 0 6 20 3 240 2 940 300 300 15 0 6 48 3 400 2 980 300 300 20 0 6 70 3 800 2 980 300 300 30 0 6 75 3 810 2 980 300 300 40 0 8 00 4 660 3 360 1000 1000 kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk After finishing with the crustal model it is time for the user to give some information related to the event he wants to analyze this is done by pressing Event I nfo in the main form Fig 3 Event Info eventinfo f x Event Info Lat Deg Min Lon Deg Min Origin Time 38 00 30 00 21 00 30 00 DDMM gt DDEG Hour Lat Deg Lon Deg Depth km 37 7059 20 9298 10 Comm
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