USGS/SLU Moment Tensor Solution ENS 2019/06/18 01:48:16:0 29.48 -104.03 5.0 3.9 Texas Stations used: EP.KIDD TX.ALPN TX.DRIO TX.MB02 TX.MNHN TX.ODSA TX.PB05 TX.PB06 TX.PB11 TX.PECS TX.SAND TX.SGCY TX.VHRN US.JCT US.MNTX Filtering commands used: cut o DIST/3.3 -30 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.10 n 3 br c 0.12 0.25 n 4 p 2 Best Fitting Double Couple Mo = 3.76e+21 dyne-cm Mw = 3.65 Z = 8 km Plane Strike Dip Rake NP1 355 70 -70 NP2 128 28 -133 Principal Axes: Axis Value Plunge Azimuth T 3.76e+21 22 70 N 0.00e+00 19 168 P -3.76e+21 60 294 Moment Tensor: (dyne-cm) Component Value Mxx 2.27e+20 Mxy 1.39e+21 Mxz -2.02e+20 Myy 2.04e+21 Myz 2.73e+21 Mzz -2.27e+21 ------######## -----------########### ---------------############# -----------------############# --------------------############## #--------------------############### #----------------------############### ##----------------------########## ### ##---------- ----------######### T ### ###---------- P ----------######### #### ####--------- ----------################ ####----------------------################ #####---------------------################ #####--------------------############### ######-------------------############### ######------------------############## #######----------------############# ########--------------############ #########----------########### ############------#######--- ##############-------- #########----- Global CMT Convention Moment Tensor: R T P -2.27e+21 -2.02e+20 -2.73e+21 -2.02e+20 2.27e+20 -1.39e+21 -2.73e+21 -1.39e+21 2.04e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20190618014816/index.html |
STK = -5 DIP = 70 RAKE = -70 MW = 3.65 HS = 8.0
The NDK file is 20190618014816.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2019/06/18 01:48:16:0 29.48 -104.03 5.0 3.9 Texas Stations used: EP.KIDD TX.ALPN TX.DRIO TX.MB02 TX.MNHN TX.ODSA TX.PB05 TX.PB06 TX.PB11 TX.PECS TX.SAND TX.SGCY TX.VHRN US.JCT US.MNTX Filtering commands used: cut o DIST/3.3 -30 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.10 n 3 br c 0.12 0.25 n 4 p 2 Best Fitting Double Couple Mo = 3.76e+21 dyne-cm Mw = 3.65 Z = 8 km Plane Strike Dip Rake NP1 355 70 -70 NP2 128 28 -133 Principal Axes: Axis Value Plunge Azimuth T 3.76e+21 22 70 N 0.00e+00 19 168 P -3.76e+21 60 294 Moment Tensor: (dyne-cm) Component Value Mxx 2.27e+20 Mxy 1.39e+21 Mxz -2.02e+20 Myy 2.04e+21 Myz 2.73e+21 Mzz -2.27e+21 ------######## -----------########### ---------------############# -----------------############# --------------------############## #--------------------############### #----------------------############### ##----------------------########## ### ##---------- ----------######### T ### ###---------- P ----------######### #### ####--------- ----------################ ####----------------------################ #####---------------------################ #####--------------------############### ######-------------------############### ######------------------############## #######----------------############# ########--------------############ #########----------########### ############------#######--- ##############-------- #########----- Global CMT Convention Moment Tensor: R T P -2.27e+21 -2.02e+20 -2.73e+21 -2.02e+20 2.27e+20 -1.39e+21 -2.73e+21 -1.39e+21 2.04e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20190618014816/index.html |
(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 -30 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.10 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 1.0 180 70 -15 3.19 0.3073 WVFGRD96 2.0 185 45 -60 3.45 0.4879 WVFGRD96 3.0 185 55 -55 3.47 0.5258 WVFGRD96 4.0 195 60 -50 3.50 0.5500 WVFGRD96 5.0 0 75 -75 3.61 0.5959 WVFGRD96 6.0 0 75 -70 3.60 0.6201 WVFGRD96 7.0 0 70 -70 3.60 0.6301 WVFGRD96 8.0 -5 70 -70 3.65 0.6394 WVFGRD96 9.0 0 75 -65 3.64 0.6389 WVFGRD96 10.0 220 70 60 3.64 0.6335 WVFGRD96 11.0 220 70 60 3.65 0.6340 WVFGRD96 12.0 35 70 50 3.63 0.6329 WVFGRD96 13.0 35 70 50 3.64 0.6302 WVFGRD96 14.0 35 70 50 3.65 0.6268 WVFGRD96 15.0 35 70 50 3.66 0.6222 WVFGRD96 16.0 35 70 50 3.67 0.6167 WVFGRD96 17.0 35 70 50 3.68 0.6097 WVFGRD96 18.0 35 75 50 3.70 0.6023 WVFGRD96 19.0 30 75 50 3.71 0.5943 WVFGRD96 20.0 30 75 50 3.72 0.5859 WVFGRD96 21.0 30 75 50 3.73 0.5766 WVFGRD96 22.0 30 75 50 3.74 0.5671 WVFGRD96 23.0 30 75 50 3.75 0.5564 WVFGRD96 24.0 30 75 55 3.77 0.5458 WVFGRD96 25.0 30 75 55 3.78 0.5341 WVFGRD96 26.0 30 75 55 3.79 0.5225 WVFGRD96 27.0 30 75 55 3.80 0.5102 WVFGRD96 28.0 30 75 55 3.80 0.4978 WVFGRD96 29.0 30 75 55 3.81 0.4854
The best solution is
WVFGRD96 8.0 -5 70 -70 3.65 0.6394
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 -30 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.10 n 3 br c 0.12 0.25 n 4 p 2
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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: