TDMTW

A full moment tensor solver

Focal mechanisms is computed using the full-waveform time-domain moment tensor (TDMT) technique (Dreger and Helmberger 1993), which implemented at the Geological Survey of Israel. Data are extracted by a magnitude dependent time windows starting 80 s before the event origin time, corrected for instrument response and the horizontal components are rotated to great circle path. Green’s functions are computed using the frequency-wavenumber integration code (FKPROG) of Saikia (1994) based on the Israel velocity model of Gitterman et al. (2002) with a 10 Hz sampling rate. This velocity model can be updated and recalculated using your own velocity model. See below for more details.

Green’s functions are band-pass filtered in the frequency band of 0.06–0.1 Hz for earthquake with magnitude 3.0≤MW≤4.0, and 0.5–1.0 Hz for MW≤2.9 in order to capture the high frequency seismic energy content of smaller magnitude earthquakes. This can be modified manually using -fmin and -fmax on the command line.

The best result is achieved through a grid-search on the depth and choosing the moment tensor solution and centroid depth for which the variance reduction (VR) is at maximum.

Dreger, D.S., Helmberger, D. V., 1993. Determination of source parameters at regional distances with three- component sparse network data. J. Geophys. Res. 98, 8107–8125. https://doi.org/10.1029/93JB00023

Gitterman, Y., Pinsky, V., Shapira, A., Ergin, M., Kalafat, D., Gurbuz, G., Solomi, K., 2002. Improvement in detection, location, and identification of small events through joint data analysis by seismic stations in the Middle East/Eastern Mediterranean region 13. https://doi.org/DTRA01-00-C-0119

Saikia, C.K., 1994. Modified frequency‐wavenumber algorithm for regional seismograms using Filon’s quadrature: modelling of Lg waves in eastern North America. Geophys. J. Int. 118, 142–158. https://doi.org/10.1111/j.1365-246X.1994.tb04680.x

Wetzler, N., Shalev, E., Göbel, T., Amelung, F., Kurzon, I., Lyakhovsky, V., Brodsky, E.E., 2019. Earthquake swarms triggered by groundwater extraction near the Dead Sea Fault. Geophys. Res. Lett. 46, 2019GL083491. https://doi.org/10.1029/2019GL083491

Please don't forget to cite if you use this code:

Wetzler, N., Sagy, A., Marco, S., Reches, Z., 2021. Asymmetry of faults and stress patterns within the Dead Sea basin as displayed by seismological analysis. Tectonophysics 229069. https://doi.org/10.1016/j.tecto.2021.229069

or

Wetzler, N., Shalev, E., Göbel, T., Amelung, F., Kurzon, I., Lyakhovsky, V., Brodsky, E.E., 2019. Earthquake swarms triggered by groundwater extraction near the Dead Sea Fault. Geophys. Res. Lett. 46, 2019GL083491. https://doi.org/10.1029/2019GL083491

Run

As a test case I chose one of the M4 along the main Dead Sea Transform - a left lateral strike-slip fault system. Use this line on your command line from your /MT folder:

python3.6 tdmtw.py -ot 2021-06-15T23:08:54 -lat 30.099 -lon 35.178 -d 21 -m 4.1 -c GFZ

-ot: Origine time (2021-06-15T23:08:54 - string)

-lat: Latitude of the earthquake (30.099 - float)

-lon: Longitude of the earthquake (35.178 - float)

-d: Depth (4 - intiger)

-m: Magnitude (4.7 - float)

-c: the FDSN servers (GFZ,IRIS,... - you can use multiple providers by using commas)

Optional parameters:

-fmin: the low bp filter frequency

-fmax: the upper bp filter frequency

For more information about this event: https://earthquake.co.il/en/earthquake/feltInfo.php?ID=202106152307

Solution

Two solutions are

Green's Functions

1. sudo apt-get install csh

you can try to use the pre-compiled file in BIN_Linux or BIN_HighSierra It is important to add the BIN_Linux or BIN_HighSierra folder to the .bashrc file edit the file: cd ~ nano .bashrc export GFBIN='pathto/TDMTW-main/' export PATH=${PATH}:${GFBIN}/GF/BIN_Linux

Or make exe file to run green functions: You can make your own GF by running GF/Py/mk_Green_functions.py

1. you need to install SAC from: http://ds.iris.edu/ds/nodes/dmc/software/downloads/sac/102-0/
2. cd GF/FK-Integration
3. make clean
4. make
5. cd UTILITIES
6. make clean
7. make

cd to /GF/Py pyhton3 mk_Green_function.py

For MacOS use: Path2_bin = pathlib.Path('../BIN_HighSierra').resolve()

For Linux use: Path2_bin = pathlib.Path('../BIN_Linux').resolve()

Velocity model is used from GF/models/ .Use Gitt02.csv as a tamplate

Or you can download the compressed Israel GF from https://figshare.com/articles/dataset/MSEED_GF_files/25567293

Customization

Logo - please free to change to your preferred logo. The logo is placed in the /MT/Layers/Logo.png

Faults - Global faults are ploted from the compilation of Bird (2002) http://peterbird.name/publications/2003_pb2002/2003_pb2002.htm . The layer is a shapefile in /MT/Layers/PB2002_boundaries.shp

Documantation is still in progress... More shold be added in the near future

Please contact me directly if you have any questions: nadav.wetzler@gmail.com

Cheers,

Nadav