This tutorial provides a complete data set for regional moment tensor inversion.
Download the following:
After downloading, execute the following steps:
- Unpack the gzip archives:
gunzip -c GREEN.tgz | tar xvf -
gunzip -c MECH.NA.tgz | tar xvf -
cd RMT/MECH.NA ; gunzip -c ../../0XXXREG.tgz | tar xf - [corrected 20 JUN 2019]
This will create the following directory structure:
| |--- CUS.REG
| |--- Models
- Determine the absolute PATH to the GREEN directory, e.g.,
For example on my system the response of this command will be
- Set the environment parameter GREENDIR in the .bashrc
file if you use the bash shell. [If you use another shell, set up something similar]. The line to be added to .bashrc for the parameter above is
- Refresh the environment
Note this will be done automatically when you login again.
- Run the souce inversion
The PDF document MomentTensorCourse.pdf provides details on the steps required to perform a regional moment tensor inversion using a grid-search technique.
If you must skip reading the tutorial, do the following:
cp RAW/*seed /home/cps/MTTEST/RMT/MECH.NA/20080418093700/20080418093700
rdseed -f ../*.seed -R -d -o 1
- On your system the absolute path will be different. So you may see something like /Users/rbh/PROGRAMS.310t/MOMENT_TENSORMECH.NA/20080418093700/20080418093700
When the computations have finished point your browser to the HTML.REG directory, e.g., file:///home/cps/MTTEST/RMT/MECH.NA/20080418093700/HTML.REG/index.html for the machine that I used.
- You may get some error messages if your do not have GMT 4 installed (the scripts will have to be changed for GMT5), and do not have the database of previous moment tensors, or the magnitde computation codes
The Greens functions distributed for this example are only the subset of distances required for the tutorial. The reason that a complete set is not provide is because of the large size of the download file.
In the directory RMT/GREEN/CUS.REG is a shell script DOIT.WK.big which computes Greens functions at finer distance intervals out to 790 km.
If you wish to work with another veolocty model, do the following:
- Create the model and place it in $GREENDIR/Models, e.g., NEW.mod
- Create a new directory for the Greens functions, cd $GREENDIR ; mkdir NEW.REG
- Copy the DOIT.WK and MKW scripts from the CUS.REG directory to the NEW.REG directory
- Carefully edit the DOIT.WK script in NEW.REG to change references of CUS to NEW. Also select the distances for which the Green's functions are to be computed. You will note in the script that at shorter distances 512 point time series are used and 1024 at larger distances. If the NEW.mod has lower velocites near the surface, as in the WUS.mod, the 1024 point synthetics will have to tbe applied at shorter distances.
Updates May 9, 2016
The 0XXXREG now contains prototypes for comptuoing ML and mLg as well as for applying the grid search for the full and deviaoric moment tensors.
The use of these scripts is illustrated at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20160307004336/index.html. The differences are as follow.
The EVENT directory will now contrin the ML.REG and MLG.REG subdirectories. If the EVETN/EVENT/FINAL/rotated_sac_files has not been removed,
will compute ML and put the results in the HTML.REG directory.
Currently my DOSETUP will also create the directories EVENT/MTGRD.REG, EVENT/MTGRD.REG.DC and EVENT.MTGRD.REG.DEV. The grid search for the best double couple solution will give the same results at the use of wvfgrd96 in the EVENT/GRD.REG directory. The deviatoric grid search takes longer since the search is over 4 parameters instead of 3. The full moment tensor search is ove five parameters and will take much, much longer than for the double couple search. So, do the following: (a) copy the DOSTA from GRD.REG to the MTGRD.REG.DEV. Edit the DOMTGRD files to select the depth ranges. In the case of the full moment tensor, just do a few depths about the best depth for the deviatoric solution.
Besides Computer Programs in Seismology, you will require the following:
- ImageMagick package to convert PostScript to PNG
- GMT - to make maps
Last changed April 15, 2012