USGS/SLU Moment Tensor Solution ENS 2022/07/21 13:35:58:0 31.68 -104.42 5.8 4.7 Texas Stations used: 4O.MID02 EP.KIDD GM.NMP25 GM.NMP41 GM.NMP44 GM.NMP45 GM.NMP53 IM.TX31 IU.ANMO N4.MSTX SC.121A SC.Y22A TX.ALPN TX.DKNS TX.MB01 TX.MB04 TX.MB05 TX.MB06 TX.MB09 TX.MNHN TX.ODSA TX.PB01 TX.PB05 TX.PB06 TX.PB11 TX.PB21 TX.PECS TX.POST TX.SAND TX.SGCY TX.SN07 TX.SN08 TX.VHRN US.MNTX Filtering commands used: cut o DIST/3.3 -40 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.08 n 3 Best Fitting Double Couple Mo = 3.94e+22 dyne-cm Mw = 4.33 Z = 8 km Plane Strike Dip Rake NP1 110 50 -80 NP2 275 41 -102 Principal Axes: Axis Value Plunge Azimuth T 3.94e+22 5 193 N 0.00e+00 8 284 P -3.94e+22 81 73 Moment Tensor: (dyne-cm) Component Value Mxx 3.71e+22 Mxy 8.26e+21 Mxz -4.82e+21 Myy 1.10e+21 Myz -6.43e+21 Mzz -3.82e+22 ############## ###################### ############################ ############################## #############------############### #######--------------------######### ####----------------------------###### -##--------------------------------##### -------------------------------------### -##------------------- --------------### ####------------------ P ----------------# #####----------------- ----------------# #######----------------------------------- ########-------------------------------- ###########----------------------------- #############------------------------# #################---------------#### ################################## ############################## ############################ ##### ############## # T ########## Global CMT Convention Moment Tensor: R T P -3.82e+22 -4.82e+21 6.43e+21 -4.82e+21 3.71e+22 -8.26e+21 6.43e+21 -8.26e+21 1.10e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20220721133558/index.html |
STK = 110 DIP = 50 RAKE = -80 MW = 4.33 HS = 8.0
The NDK file is 20220721133558.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2022/07/21 13:35:58:0 31.68 -104.42 5.8 4.7 Texas Stations used: 4O.MID02 EP.KIDD GM.NMP25 GM.NMP41 GM.NMP44 GM.NMP45 GM.NMP53 IM.TX31 IU.ANMO N4.MSTX SC.121A SC.Y22A TX.ALPN TX.DKNS TX.MB01 TX.MB04 TX.MB05 TX.MB06 TX.MB09 TX.MNHN TX.ODSA TX.PB01 TX.PB05 TX.PB06 TX.PB11 TX.PB21 TX.PECS TX.POST TX.SAND TX.SGCY TX.SN07 TX.SN08 TX.VHRN US.MNTX Filtering commands used: cut o DIST/3.3 -40 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.08 n 3 Best Fitting Double Couple Mo = 3.94e+22 dyne-cm Mw = 4.33 Z = 8 km Plane Strike Dip Rake NP1 110 50 -80 NP2 275 41 -102 Principal Axes: Axis Value Plunge Azimuth T 3.94e+22 5 193 N 0.00e+00 8 284 P -3.94e+22 81 73 Moment Tensor: (dyne-cm) Component Value Mxx 3.71e+22 Mxy 8.26e+21 Mxz -4.82e+21 Myy 1.10e+21 Myz -6.43e+21 Mzz -3.82e+22 ############## ###################### ############################ ############################## #############------############### #######--------------------######### ####----------------------------###### -##--------------------------------##### -------------------------------------### -##------------------- --------------### ####------------------ P ----------------# #####----------------- ----------------# #######----------------------------------- ########-------------------------------- ###########----------------------------- #############------------------------# #################---------------#### ################################## ############################## ############################ ##### ############## # T ########## Global CMT Convention Moment Tensor: R T P -3.82e+22 -4.82e+21 6.43e+21 -4.82e+21 3.71e+22 -8.26e+21 6.43e+21 -8.26e+21 1.10e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20220721133558/index.html |
Regional Moment Tensor (Mwr) Moment 3.731e+15 N-m Magnitude 4.31 Mwr Depth 5.0 km Percent DC 92% Half Duration - Catalog US Data Source US 2 Contributor US 2 Nodal Planes Plane Strike Dip Rake NP1 279 37 -94 NP2 104 53 -87 Principal Axes Axis Value Plunge Azimuth T 3.805e+15 N-m 8 192 N -0.153e+15 N-m 3 282 P -3.653e+15 N-m 82 31 |
(a) mLg computed using the IASPEI formula; (b) mLg residuals ; the values used for the trimmed mean are indicated.
(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.
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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 -40 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.08 n 3The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT WVFGRD96 1.0 150 70 -35 3.91 0.2820 WVFGRD96 2.0 140 65 -45 4.06 0.3665 WVFGRD96 3.0 140 70 -50 4.13 0.4396 WVFGRD96 4.0 130 60 -55 4.18 0.5010 WVFGRD96 5.0 115 50 -70 4.23 0.5450 WVFGRD96 6.0 110 45 -75 4.25 0.5667 WVFGRD96 7.0 115 45 -70 4.26 0.5653 WVFGRD96 8.0 110 50 -80 4.33 0.5913 WVFGRD96 9.0 120 50 -65 4.31 0.5690 WVFGRD96 10.0 135 55 -45 4.29 0.5412 WVFGRD96 11.0 145 70 -30 4.27 0.5225 WVFGRD96 12.0 335 75 20 4.28 0.5078 WVFGRD96 13.0 335 75 20 4.29 0.4975 WVFGRD96 14.0 335 75 20 4.30 0.4860 WVFGRD96 15.0 330 80 20 4.30 0.4730 WVFGRD96 16.0 330 80 20 4.31 0.4604 WVFGRD96 17.0 330 85 20 4.32 0.4481 WVFGRD96 18.0 330 85 20 4.32 0.4358 WVFGRD96 19.0 330 85 20 4.33 0.4236 WVFGRD96 20.0 150 90 -20 4.33 0.4115 WVFGRD96 21.0 330 85 20 4.34 0.4010 WVFGRD96 22.0 330 85 20 4.35 0.3903 WVFGRD96 23.0 330 85 20 4.35 0.3801 WVFGRD96 24.0 145 75 -20 4.36 0.3721 WVFGRD96 25.0 145 75 -20 4.37 0.3640 WVFGRD96 26.0 145 75 -20 4.37 0.3565 WVFGRD96 27.0 145 75 -20 4.38 0.3496 WVFGRD96 28.0 145 75 -20 4.38 0.3430 WVFGRD96 29.0 145 75 -20 4.39 0.3366
The best solution is
WVFGRD96 8.0 110 50 -80 4.33 0.5913
The mechanism correspond to the best fit is
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The best fit as a function of depth is given in the following figure:
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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 observed-predicted 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 -40 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.08 n 3
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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 1-D 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 0.302E-02 0.679E-02 0.00 0.00 1.00 1.00 6.1000 5.5445 3.2953 2.6089 0.349E-02 0.784E-02 0.00 0.00 1.00 1.00 13.0000 6.2708 3.7396 2.7812 0.212E-02 0.476E-02 0.00 0.00 1.00 1.00 19.0000 6.4075 3.7680 2.8223 0.111E-02 0.249E-02 0.00 0.00 1.00 1.00 0.0000 7.9000 4.6200 3.2760 0.164E-10 0.370E-10 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: