USGS/SLU Moment Tensor Solution ENS 2019/10/01 07:14:44:0 32.89 -100.86 5.0 3.8 Texas Stations used: N4.ABTX N4.MSTX N4.WHTX N4.Z35B TX.435B TX.ALPN TX.APMT TX.BRDY TX.DKNS TX.DRZT TX.MB01 TX.MB04 TX.MB05 TX.MB06 TX.MNHN TX.ODSA TX.OZNA TX.PECS TX.PLPT TX.POST TX.RTBA TX.SMWD TX.SN08 TX.WTFS US.AMTX US.JCT 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 = 4.79e+21 dyne-cm Mw = 3.72 Z = 10 km Plane Strike Dip Rake NP1 195 90 -155 NP2 105 65 0 Principal Axes: Axis Value Plunge Azimuth T 4.79e+21 17 327 N 0.00e+00 65 195 P -4.79e+21 17 63 Moment Tensor: (dyne-cm) Component Value Mxx 2.17e+21 Mxy -3.76e+21 Mxz 5.24e+20 Myy -2.17e+21 Myz -1.95e+21 Mzz 0.00e+00 ############-- ################------ ### ############---------- #### T ############----------- ###### ###########-------------- #####################----------- - #####################------------ P -- ######################------------ --- #####################------------------- ---###################-------------------- -----################--------------------- -------##############--------------------- -----------#########---------------------- --------------#####--------------------- ------------------##-----------------### -----------------##################### ---------------##################### --------------#################### -----------################### ----------################## ------################ --############ Global CMT Convention Moment Tensor: R T P 0.00e+00 5.24e+20 1.95e+21 5.24e+20 2.17e+21 3.76e+21 1.95e+21 3.76e+21 -2.17e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20191001071444/index.html |
STK = 105 DIP = 65 RAKE = 0 MW = 3.72 HS = 10.0
The NDK file is 20191001071444.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2019/10/01 07:14:44:0 32.89 -100.86 5.0 3.8 Texas Stations used: N4.ABTX N4.MSTX N4.WHTX N4.Z35B TX.435B TX.ALPN TX.APMT TX.BRDY TX.DKNS TX.DRZT TX.MB01 TX.MB04 TX.MB05 TX.MB06 TX.MNHN TX.ODSA TX.OZNA TX.PECS TX.PLPT TX.POST TX.RTBA TX.SMWD TX.SN08 TX.WTFS US.AMTX US.JCT 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 = 4.79e+21 dyne-cm Mw = 3.72 Z = 10 km Plane Strike Dip Rake NP1 195 90 -155 NP2 105 65 0 Principal Axes: Axis Value Plunge Azimuth T 4.79e+21 17 327 N 0.00e+00 65 195 P -4.79e+21 17 63 Moment Tensor: (dyne-cm) Component Value Mxx 2.17e+21 Mxy -3.76e+21 Mxz 5.24e+20 Myy -2.17e+21 Myz -1.95e+21 Mzz 0.00e+00 ############-- ################------ ### ############---------- #### T ############----------- ###### ###########-------------- #####################----------- - #####################------------ P -- ######################------------ --- #####################------------------- ---###################-------------------- -----################--------------------- -------##############--------------------- -----------#########---------------------- --------------#####--------------------- ------------------##-----------------### -----------------##################### ---------------##################### --------------#################### -----------################### ----------################## ------################ --############ Global CMT Convention Moment Tensor: R T P 0.00e+00 5.24e+20 1.95e+21 5.24e+20 2.17e+21 3.76e+21 1.95e+21 3.76e+21 -2.17e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20191001071444/index.html |
Regional Moment Tensor (Mwr) Moment 5.436e+14 N-m Magnitude 3.76 Mwr Depth 3.0 km Percent DC 84% Half Duration - Catalog US Data Source US 1 Contributor US 1 Nodal Planes Plane Strike Dip Rake NP1 195 82 -160 NP2 102 70 -9 Principal Axes Axis Value Plunge Azimuth T 5.648e+14 N-m 8 327 N -0.453e+14 N-m 69 216 P -5.195e+14 N-m 20 60 |
(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 1.0 200 85 -20 3.36 0.3446 WVFGRD96 2.0 200 75 35 3.52 0.4117 WVFGRD96 3.0 205 65 35 3.57 0.4379 WVFGRD96 4.0 195 75 -30 3.58 0.4466 WVFGRD96 5.0 105 65 -15 3.60 0.4494 WVFGRD96 6.0 105 65 -5 3.62 0.4614 WVFGRD96 7.0 105 65 0 3.65 0.4717 WVFGRD96 8.0 105 65 -5 3.69 0.4803 WVFGRD96 9.0 105 65 0 3.71 0.4858 WVFGRD96 10.0 105 65 0 3.72 0.4863 WVFGRD96 11.0 105 70 0 3.73 0.4835 WVFGRD96 12.0 110 70 10 3.75 0.4801 WVFGRD96 13.0 110 70 10 3.76 0.4758 WVFGRD96 14.0 110 70 10 3.77 0.4704 WVFGRD96 15.0 110 75 15 3.78 0.4654 WVFGRD96 16.0 110 75 15 3.79 0.4605 WVFGRD96 17.0 110 80 15 3.80 0.4561 WVFGRD96 18.0 110 80 15 3.81 0.4523 WVFGRD96 19.0 110 80 20 3.82 0.4489 WVFGRD96 20.0 285 80 -20 3.84 0.4501 WVFGRD96 21.0 285 80 -20 3.85 0.4488 WVFGRD96 22.0 285 80 -20 3.86 0.4473 WVFGRD96 23.0 285 80 -20 3.87 0.4466 WVFGRD96 24.0 285 80 -20 3.88 0.4465 WVFGRD96 25.0 285 80 -20 3.89 0.4470 WVFGRD96 26.0 285 80 -20 3.90 0.4475 WVFGRD96 27.0 285 80 -20 3.90 0.4484 WVFGRD96 28.0 285 80 -20 3.91 0.4491 WVFGRD96 29.0 285 80 -20 3.92 0.4492
The best solution is
WVFGRD96 10.0 105 65 0 3.72 0.4863
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: