USGS/SLU Moment Tensor Solution ENS 2021/09/06 14:52:35:0 31.61 104.24 6.5 3.3 Texas Stations used: GM.NMP25 TX.PB05 TX.PB11 TX.PB28 TX.PECS TX.VHRN US.MNTX Filtering commands used: cut o DIST/3.3 30 o DIST/3.3 +40 rtr taper w 0.1 hp c 0.04 n 3 lp c 0.12 n 3 br c 0.12 0.25 n 4 p 2 Best Fitting Double Couple Mo = 6.68e+20 dynecm Mw = 3.15 Z = 9 km Plane Strike Dip Rake NP1 84 60 93 NP2 270 30 85 Principal Axes: Axis Value Plunge Azimuth T 6.68e+20 15 176 N 0.00e+00 2 86 P 6.68e+20 75 346 Moment Tensor: (dynecm) Component Value Mxx 5.77e+20 Mxy 2.91e+19 Mxz 3.33e+20 Myy 6.95e+11 Myz 5.04e+19 Mzz 5.77e+20 ############## ###################### ############################ ################## ############ ######## ###### ###### # # # P # #  ### ####### ########### #################### ###################################### #################################### ################################## ############################## ############## ########### ########### T ######## ####### #### Global CMT Convention Moment Tensor: R T P 5.77e+20 3.33e+20 5.04e+19 3.33e+20 5.77e+20 2.91e+19 5.04e+19 2.91e+19 6.95e+11 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20210906145235/index.html 
STK = 270 DIP = 30 RAKE = 85 MW = 3.15 HS = 9.0
The NDK file is 20210906145235.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2021/09/06 14:52:35:0 31.61 104.24 6.5 3.3 Texas Stations used: GM.NMP25 TX.PB05 TX.PB11 TX.PB28 TX.PECS TX.VHRN US.MNTX Filtering commands used: cut o DIST/3.3 30 o DIST/3.3 +40 rtr taper w 0.1 hp c 0.04 n 3 lp c 0.12 n 3 br c 0.12 0.25 n 4 p 2 Best Fitting Double Couple Mo = 6.68e+20 dynecm Mw = 3.15 Z = 9 km Plane Strike Dip Rake NP1 84 60 93 NP2 270 30 85 Principal Axes: Axis Value Plunge Azimuth T 6.68e+20 15 176 N 0.00e+00 2 86 P 6.68e+20 75 346 Moment Tensor: (dynecm) Component Value Mxx 5.77e+20 Mxy 2.91e+19 Mxz 3.33e+20 Myy 6.95e+11 Myz 5.04e+19 Mzz 5.77e+20 ############## ###################### ############################ ################## ############ ######## ###### ###### # # # P # #  ### ####### ########### #################### ###################################### #################################### ################################## ############################## ############## ########### ########### T ######## ####### #### Global CMT Convention Moment Tensor: R T P 5.77e+20 3.33e+20 5.04e+19 3.33e+20 5.77e+20 2.91e+19 5.04e+19 2.91e+19 6.95e+11 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20210906145235/index.html 
(a) ML computed using the IASPEI formula for Horizontal components; (b) ML residuals computed using a modified IASPEI formula that accounts for path specific attenuation; the values used for the trimmed mean are indicated. The ML relation used for each figure is given at the bottom of each plot.
(a) ML computed using the IASPEI formula for Vertical components (research); (b) ML residuals computed using a modified IASPEI formula that accounts for path specific attenuation; the values used for the trimmed mean are indicated. The ML relation used for each figure is given at the bottom of each plot.
The focal mechanism was determined using broadband seismic waveforms. The location of the event and the and stations used for the waveform inversion are shown in the next figure.

The program wvfgrd96 was used with good traces observed at short distance to determine the focal mechanism, depth and seismic moment. This technique requires a high quality signal and well determined velocity model for the Green functions. To the extent that these are the quality data, this type of mechanism should be preferred over the radiation pattern technique which requires the separate step of defining the pressure and tension quadrants and the correct strike.
The observed and predicted traces are filtered using the following gsac commands:
cut o DIST/3.3 30 o DIST/3.3 +40 rtr taper w 0.1 hp c 0.04 n 3 lp c 0.12 n 3 br c 0.12 0.25 n 4 p 2The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT WVFGRD96 1.0 170 70 10 2.57 0.1111 WVFGRD96 2.0 80 45 80 2.77 0.2033 WVFGRD96 3.0 285 40 45 2.82 0.2499 WVFGRD96 4.0 285 35 45 2.90 0.3138 WVFGRD96 5.0 280 30 60 2.99 0.3570 WVFGRD96 6.0 295 35 55 3.04 0.3792 WVFGRD96 7.0 290 35 65 3.08 0.3909 WVFGRD96 8.0 280 30 75 3.14 0.3968 WVFGRD96 9.0 270 30 85 3.15 0.3978 WVFGRD96 10.0 270 30 85 3.16 0.3948 WVFGRD96 11.0 265 30 90 3.16 0.3861 WVFGRD96 12.0 265 30 90 3.16 0.3758 WVFGRD96 13.0 260 35 90 3.15 0.3686 WVFGRD96 14.0 260 35 90 3.16 0.3640 WVFGRD96 15.0 80 55 90 3.17 0.3579 WVFGRD96 16.0 85 60 85 3.18 0.3501 WVFGRD96 17.0 310 55 20 3.07 0.3477 WVFGRD96 18.0 310 55 20 3.08 0.3454 WVFGRD96 19.0 310 55 25 3.09 0.3419 WVFGRD96 20.0 310 55 25 3.10 0.3378 WVFGRD96 21.0 310 55 20 3.10 0.3330 WVFGRD96 22.0 310 55 20 3.11 0.3277 WVFGRD96 23.0 310 55 20 3.11 0.3213 WVFGRD96 24.0 310 55 20 3.11 0.3159 WVFGRD96 25.0 310 60 25 3.12 0.3087 WVFGRD96 26.0 95 70 60 3.24 0.3058 WVFGRD96 27.0 95 70 60 3.24 0.3021 WVFGRD96 28.0 290 45 35 3.16 0.2957 WVFGRD96 29.0 290 45 35 3.16 0.2939
The best solution is
WVFGRD96 9.0 270 30 85 3.15 0.3978
The mechanism correspond to the best fit is

The best fit as a function of depth is given in the following figure:

The comparison of the observed and predicted waveforms is given in the next figure. The red traces are the observed and the blue are the predicted. Each observedpredicted component is plotted to the same scale and peak amplitudes are indicated by the numbers to the left of each trace. A pair of numbers is given in black at the right of each predicted traces. The upper number it the time shift required for maximum correlation between the observed and predicted traces. This time shift is required because the synthetics are not computed at exactly the same distance as the observed and because the velocity model used in the predictions may not be perfect. A positive time shift indicates that the prediction is too fast and should be delayed to match the observed trace (shift to the right in this figure). A negative value indicates that the prediction is too slow. The lower number gives the percentage of variance reduction to characterize the individual goodness of fit (100% indicates a perfect fit).
The bandpass filter used in the processing and for the display was
cut o DIST/3.3 30 o DIST/3.3 +40 rtr taper w 0.1 hp c 0.04 n 3 lp c 0.12 n 3 br c 0.12 0.25 n 4 p 2

Focal mechanism sensitivity at the preferred depth. The red color indicates a very good fit to thewavefroms. Each solution is plotted as a vector at a given value of strike and dip with the angle of the vector representing the rake angle, measured, with respect to the upward vertical (N) in the figure. 
A check on the assumed source location is possible by looking at the time shifts between the observed and predicted traces. The time shifts for waveform matching arise for several reasons:
Time_shift = A + B cos Azimuth + C Sin Azimuth
The time shifts for this inversion lead to the next figure:
The derived shift in origin time and epicentral coordinates are given at the bottom of the figure.
Thanks also to the many seismic network operators whose dedication make this effort possible: University of Nevada Reno, University of Alaska, University of Washington, Oregon State University, University of Utah, Montana Bureau of Mines, UC Berkely, Caltech, UC San Diego, Saint Louis University, University of Memphis, Lamont Doherty Earth Observatory, the Oklahoma Geological Survey, TexNet, the Iris stations, the Transportable Array of EarthScope and other networks.
The WUS.model used for the waveform synthetic seismograms and for the surface wave eigenfunctions and dispersion is as follows:
MODEL.01 Model after 8 iterations ISOTROPIC KGS FLAT EARTH 1D CONSTANT VELOCITY LINE08 LINE09 LINE10 LINE11 H(KM) VP(KM/S) VS(KM/S) RHO(GM/CC) QP QS ETAP ETAS FREFP FREFS 1.9000 3.4065 2.0089 2.2150 0.302E02 0.679E02 0.00 0.00 1.00 1.00 6.1000 5.5445 3.2953 2.6089 0.349E02 0.784E02 0.00 0.00 1.00 1.00 13.0000 6.2708 3.7396 2.7812 0.212E02 0.476E02 0.00 0.00 1.00 1.00 19.0000 6.4075 3.7680 2.8223 0.111E02 0.249E02 0.00 0.00 1.00 1.00 0.0000 7.9000 4.6200 3.2760 0.164E10 0.370E10 0.00 0.00 1.00 1.00
Here we tabulate the reasons for not using certain digital data sets
The following stations did not have a valid response files: