User Manual
Contents
1. Documentation version April 16 2015 FMINEAR computation webservice Use of the Service Step 1 data uploading Connect to http source unice fr 8080 FMNEAR_website fmnear html You access to the webservice home page In the upper part of the page you have a link to access the service itself On the new page displayed you can download the documentation user manual Data and velocity model as well as an example of dataset presently an earthquake in the French Pyrenees with strong motion records You can enter your email address optional used to send you an email with the link to the results when computation is finished To upload your data archive from your local computer tape the path and file name or using the search directories then send Please see the document Data and velocity model for data format Step 2 parameters and options A new page is displayed with all the parameters and options You may check that the parameters are correctly retrieved from the SAC hearders In the station list vel or acc is indicated after the station name depending on whether the data are in velocity or acceleration taken from the file names see Data section The P wave pick times appears as 0 if not picked beforehand a variable of the SAC headers undefined see Data section O is used here as an indication for undefined pick time If this is the case FMNEAR will searc2. ay fix the focal mechanism Enter strike dip rake values in the input boxes You may force the codes to keep all components see remark 1 below even those associated with a poor waveform fit You may define a pre event time Automatic picking will then start after pre event time Be sure that pre event time is smaller than the P wave arrival at the nearest station This option is to avoid picking on noise events or pre shocks that may be present in the pre event time window This will be used only for those stations whose pick time is O undefined pick time A map showing the all stations included in the archive white triangles and the epicentre orange star is displayed below the options When all values and options are OK for you click on the send button at the bottom of the page Remark 1 if you choose the Use all components option and if the filtering option is Auto automatic filtering some components may be nonetheless discarded if the search for optimal filtering does not end up with an acceptable frequency band The only way to insure that all components will be kept in the process is to tick the Use all components checkbox and impose a fixed band of filtering see above Of course in that case very poor waveform modelling may occur for components affected by a high level of noise in the frequency band imposed Remark 2 if you want to force automatic picking of the P wave P wave pick time sh
3. h to pick the P wave automatically next step Distance is the horizontal distance in km from the epicentre to the station and azimuth is the azimuth in degrees of the epicentre to station direction with respect to the North You can click on the station name appears as a link it will open a window showing the raw waveforms of that station You may go directly to the send button at the bottom of the page if you are satisfied with the parameters and default options If you want you may modify the earthquake parameters latitude longitude depth magnitude You may define a fixed frequency band for the filtering of the waveforms default choice Auto means that filtering will be automatically defined for each component individually either by choosing a range in the running menu or by ticking the checkbox Define custom band and providing the minimum and maximum frequencies in the input boxes left and right respectively If you fix the frequency band this single range will be applied to all components of all the stations You may use the checkbox select all stations to select tick or unselect untick all stations You may use the checkboxes at the end of each station lines to select tick or unselect untick stations individually Four options are proposed at the bottom of the page tick checkboxes to fix You may fix the focal depth otherwise the FMNEAR codes will try to optimize depth You m
4. mechanism the stations retained in the modelling in green and the stations not used in white Modelling of the waveforms appears as a series of graphs station by station The three components of a given station are shown on the same line in the order N E Z from left to right Names of components appear as XSTATv for stations equipped with velocimeters and XSTATa for stations equipped with accelerometers where X is either N E or Z However waveforms are displayed in displacement with amplitude in centimetres vertical axis Time is in seconds horizontal axis STAT is the name of the station Near the bottom of the page the list of selected stations before computation is printed with corresponding parameters P time is either the input pick time originally included in the SAC header or the time automatically picked or 0 if the automatic picker failed This list may display more stations than finally retained by the programs The distribution of seismic moment is provided for earthquakes with initial magnitude larger or equal to 5 5 If you want to save the results click on the link Download result archive Remark 3 it may happen that the program does not provide any result The most common cause is that stations were discarded but the program This may happen because no adequate filtering could be found or because the waveforms could not be modelled properly If this happens case check the filteri
5. ng parameters think about signal noise ratio as a function of magnitude and distance far away stations will be commonly discarded for small magnitudes Step 4 looping By clicking on Looping going back to parameters and options you can loop with the same dataset and run a new computation with different parameters and or a different selection of stations and or different options If stations were not initially picked from the SAC header variable a see Data section the pick time determined automatically is printed in the last column of the station list If automatic picking failed pick time remains 0 If you publish show results obtained with this webservice please include reference FMNEAR webservice Delouis Gerakis Deschamps Geoazur Observatoire de la C te d Azur Concerning the method FMNEAR please include reference to the article Delouis B 2014 FMNEAR determination of focal mechanism and first estimate of rupture directivity using near source records and a linear distribution of point sources Bulletin of the Seismological Society of America 104 3 1479 1500 doi 10 1785 0120130151 Bertrand Delouis delouis geoazur unice fr
6. ould be 0 Step 3 Checking the results On the new page copy the process number and click on back to home page On the home page paste the process number in the check your process box and then click on check If computation is not finished you obtain the message Not Yet Use the back page of your navigator and check again latter If computation is finished you obtain a page displaying the results You will find the following The strike dip rake of the best focal mechanism solution found or fixed if you used this option The RMS which is the normalized Root Mean Square misfit function of the waveforms The lower the RMS nearer to zero the best is the waveform fit Variance reduction in percentage would be 1 RMS 100 The selected depth which is the depth optimized by waveform modelling except if you used the option of fixing depth The number of components retained at the end It is considered that the frequency band should be larger than 0 015Hz to be meaningful otherwise the frequency range is too narrow The index of confidence in which is a measure of the quality and uniqueness of the solution solution considered reliable when index gt 70 generally The index will not be computed if the option of fixing the focal mechanism is used The moment magnitude My issued from the waveform modelling associated with the best solution A map is shown with the focal
Download Pdf Manuals
Related Search