USGS/SLU Moment Tensor Solution ENS 2022/08/11 07:17:16:0 31.68 -104.43 6.6 4.5 Texas Stations used: 4O.MID02 GM.NMP25 GM.NMP41 GM.NMP44 GM.NMP45 GM.NMP53 IM.TX31 IU.ANMO N4.MSTX SC.121A SC.Y22A TX.ALPN TX.APMT TX.DKNS TX.MB01 TX.MB04 TX.MB09 TX.MNHN TX.ODSA TX.PB01 TX.PB05 TX.PB11 TX.PB21 TX.PECS 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 = 1.97e+22 dyne-cm Mw = 4.13 Z = 8 km Plane Strike Dip Rake NP1 100 55 -95 NP2 289 35 -83 Principal Axes: Axis Value Plunge Azimuth T 1.97e+22 10 194 N 0.00e+00 4 103 P -1.97e+22 79 351 Moment Tensor: (dyne-cm) Component Value Mxx 1.74e+22 Mxy 4.48e+21 Mxz -6.79e+21 Myy 1.04e+21 Myz -1.96e+20 Mzz -1.85e+22 ############## ###################### ############################ ########-------############### ####-------------------########### ##--------------------------######## #------------------------------####### ----------------------------------###### ------------------ ---------------#### #------------------ P ----------------#### ##----------------- -----------------### ####------------------------------------## ######----------------------------------## #######--------------------------------# ###########-------------------------#### ################---------------####### #################################### ################################## ############################## ######## ################# ##### T ############## # ########## Global CMT Convention Moment Tensor: R T P -1.85e+22 -6.79e+21 1.96e+20 -6.79e+21 1.74e+22 -4.48e+21 1.96e+20 -4.48e+21 1.04e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20220811071716/index.html |
STK = 100 DIP = 55 RAKE = -95 MW = 4.13 HS = 8.0
The NDK file is 20220811071716.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2022/08/11 07:17:16:0 31.68 -104.43 6.6 4.5 Texas Stations used: 4O.MID02 GM.NMP25 GM.NMP41 GM.NMP44 GM.NMP45 GM.NMP53 IM.TX31 IU.ANMO N4.MSTX SC.121A SC.Y22A TX.ALPN TX.APMT TX.DKNS TX.MB01 TX.MB04 TX.MB09 TX.MNHN TX.ODSA TX.PB01 TX.PB05 TX.PB11 TX.PB21 TX.PECS 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 = 1.97e+22 dyne-cm Mw = 4.13 Z = 8 km Plane Strike Dip Rake NP1 100 55 -95 NP2 289 35 -83 Principal Axes: Axis Value Plunge Azimuth T 1.97e+22 10 194 N 0.00e+00 4 103 P -1.97e+22 79 351 Moment Tensor: (dyne-cm) Component Value Mxx 1.74e+22 Mxy 4.48e+21 Mxz -6.79e+21 Myy 1.04e+21 Myz -1.96e+20 Mzz -1.85e+22 ############## ###################### ############################ ########-------############### ####-------------------########### ##--------------------------######## #------------------------------####### ----------------------------------###### ------------------ ---------------#### #------------------ P ----------------#### ##----------------- -----------------### ####------------------------------------## ######----------------------------------## #######--------------------------------# ###########-------------------------#### ################---------------####### #################################### ################################## ############################## ######## ################# ##### T ############## # ########## Global CMT Convention Moment Tensor: R T P -1.85e+22 -6.79e+21 1.96e+20 -6.79e+21 1.74e+22 -4.48e+21 1.96e+20 -4.48e+21 1.04e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20220811071716/index.html |
Regional Moment Tensor (Mwr) Moment 2.115e+15 N-m Magnitude 4.15 Mwr Depth 8.0 km Percent DC 91% Half Duration - Catalog US Data Source US 2 Contributor US 2 Nodal Planes Plane Strike Dip Rake NP1 283 32 -94 NP2 108 58 -88 Principal Axes Axis Value Plunge Azimuth T 2.067e+15 N-m 13 196 N 0.094e+15 N-m 2 286 P -2.161e+15 N-m 77 25 |
(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 are as follow:
DEPTH STK DIP RAKE MW FIT WVFGRD96 1.0 160 80 -30 3.70 0.2695 WVFGRD96 2.0 145 65 -45 3.86 0.3406 WVFGRD96 3.0 155 85 65 3.97 0.4065 WVFGRD96 4.0 155 80 60 3.96 0.4596 WVFGRD96 5.0 110 55 -80 4.03 0.5054 WVFGRD96 6.0 285 35 -85 4.05 0.5449 WVFGRD96 7.0 290 40 -80 4.07 0.5645 WVFGRD96 8.0 100 55 -95 4.13 0.5840 WVFGRD96 9.0 105 50 -90 4.14 0.5801 WVFGRD96 10.0 105 50 -90 4.13 0.5591 WVFGRD96 11.0 115 50 -75 4.12 0.5300 WVFGRD96 12.0 140 65 -40 4.08 0.5050 WVFGRD96 13.0 140 65 -40 4.09 0.4866 WVFGRD96 14.0 145 70 -35 4.09 0.4689 WVFGRD96 15.0 335 80 25 4.10 0.4549 WVFGRD96 16.0 335 80 25 4.10 0.4419 WVFGRD96 17.0 335 80 25 4.11 0.4290 WVFGRD96 18.0 335 80 25 4.12 0.4169 WVFGRD96 19.0 335 80 25 4.12 0.4050 WVFGRD96 20.0 335 80 30 4.12 0.3933 WVFGRD96 21.0 335 80 30 4.13 0.3824 WVFGRD96 22.0 335 80 30 4.14 0.3716 WVFGRD96 23.0 335 80 30 4.14 0.3610 WVFGRD96 24.0 335 80 30 4.15 0.3502 WVFGRD96 25.0 335 80 30 4.15 0.3400 WVFGRD96 26.0 330 80 30 4.15 0.3303 WVFGRD96 27.0 330 85 30 4.16 0.3214 WVFGRD96 28.0 330 85 30 4.16 0.3129 WVFGRD96 29.0 150 70 -20 4.18 0.3038
The best solution is
WVFGRD96 8.0 100 55 -95 4.13 0.5840
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: