USGS/SLU Moment Tensor Solution ENS 2017/10/05 00:12:01:0 36.45 -98.75 7.2 3.4 Oklahoma Stations used: GS.OK032 GS.OK035 OK.CROK OK.ELIS OK.GORE OK.HTCH OK.NOKA OK.U32A Filtering commands used: cut o DIST/3.3 -15 o DIST/3.3 +25 rtr taper w 0.1 hp c 0.04 n 3 lp c 0.15 n 3 Best Fitting Double Couple Mo = 8.51e+20 dyne-cm Mw = 3.22 Z = 7 km Plane Strike Dip Rake NP1 58 80 -165 NP2 325 75 -10 Principal Axes: Axis Value Plunge Azimuth T 8.51e+20 4 191 N 0.00e+00 72 89 P -8.51e+20 18 282 Moment Tensor: (dyne-cm) Component Value Mxx 7.85e+20 Mxy 3.12e+20 Mxz -1.04e+20 Myy -7.11e+20 Myz 2.29e+20 Mzz -7.39e+19 ############## ###################### ----######################## --------###################### ------------###################### ---------------####################- -----------------#################---- --------------------#############------- - -----------------##########--------- -- P -------------------#####------------- -- --------------------##--------------- ------------------------##---------------- ---------------------######--------------- -----------------##########------------- --------------##############------------ ---------###################---------- ----########################-------- ############################------ ##########################---- ##########################-- ###### ############# ## T ######### Global CMT Convention Moment Tensor: R T P -7.39e+19 -1.04e+20 -2.29e+20 -1.04e+20 7.85e+20 -3.12e+20 -2.29e+20 -3.12e+20 -7.11e+20 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20171005001201/index.html |
STK = 325 DIP = 75 RAKE = -10 MW = 3.22 HS = 7.0
The NDK file is 20171005001201.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2017/10/05 00:12:01:0 36.45 -98.75 7.2 3.4 Oklahoma Stations used: GS.OK032 GS.OK035 OK.CROK OK.ELIS OK.GORE OK.HTCH OK.NOKA OK.U32A Filtering commands used: cut o DIST/3.3 -15 o DIST/3.3 +25 rtr taper w 0.1 hp c 0.04 n 3 lp c 0.15 n 3 Best Fitting Double Couple Mo = 8.51e+20 dyne-cm Mw = 3.22 Z = 7 km Plane Strike Dip Rake NP1 58 80 -165 NP2 325 75 -10 Principal Axes: Axis Value Plunge Azimuth T 8.51e+20 4 191 N 0.00e+00 72 89 P -8.51e+20 18 282 Moment Tensor: (dyne-cm) Component Value Mxx 7.85e+20 Mxy 3.12e+20 Mxz -1.04e+20 Myy -7.11e+20 Myz 2.29e+20 Mzz -7.39e+19 ############## ###################### ----######################## --------###################### ------------###################### ---------------####################- -----------------#################---- --------------------#############------- - -----------------##########--------- -- P -------------------#####------------- -- --------------------##--------------- ------------------------##---------------- ---------------------######--------------- -----------------##########------------- --------------##############------------ ---------###################---------- ----########################-------- ############################------ ##########################---- ##########################-- ###### ############# ## T ######### Global CMT Convention Moment Tensor: R T P -7.39e+19 -1.04e+20 -2.29e+20 -1.04e+20 7.85e+20 -3.12e+20 -2.29e+20 -3.12e+20 -7.11e+20 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20171005001201/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 -15 o DIST/3.3 +25 rtr taper w 0.1 hp c 0.04 n 3 lp c 0.15 n 3The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT WVFGRD96 1.0 325 80 0 2.71 0.3233 WVFGRD96 2.0 150 75 20 2.92 0.4595 WVFGRD96 3.0 330 65 15 3.01 0.5244 WVFGRD96 4.0 320 65 -20 3.09 0.5751 WVFGRD96 5.0 325 70 -10 3.12 0.6079 WVFGRD96 6.0 325 70 -10 3.17 0.6232 WVFGRD96 7.0 325 75 -10 3.22 0.6237 WVFGRD96 8.0 325 70 -15 3.27 0.6107 WVFGRD96 9.0 325 70 -15 3.30 0.5911 WVFGRD96 10.0 325 70 -15 3.33 0.5654 WVFGRD96 11.0 325 70 -15 3.35 0.5379 WVFGRD96 12.0 330 75 -10 3.35 0.5101 WVFGRD96 13.0 330 80 -10 3.36 0.4817 WVFGRD96 14.0 170 30 50 3.54 0.4530 WVFGRD96 15.0 170 25 50 3.56 0.4344 WVFGRD96 16.0 170 25 50 3.57 0.4142 WVFGRD96 17.0 165 30 40 3.53 0.3927 WVFGRD96 18.0 165 30 40 3.53 0.3791 WVFGRD96 19.0 165 30 40 3.53 0.3621 WVFGRD96 20.0 160 40 30 3.49 0.3531 WVFGRD96 21.0 160 35 30 3.51 0.3513 WVFGRD96 22.0 160 40 25 3.50 0.3583 WVFGRD96 23.0 160 40 25 3.51 0.3665 WVFGRD96 24.0 35 80 55 3.69 0.3738 WVFGRD96 25.0 40 80 60 3.68 0.3846 WVFGRD96 26.0 35 85 55 3.68 0.3932 WVFGRD96 27.0 150 55 15 3.50 0.3990 WVFGRD96 28.0 150 55 15 3.51 0.4047 WVFGRD96 29.0 150 55 10 3.51 0.4109
The best solution is
WVFGRD96 7.0 325 75 -10 3.22 0.6237
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 -15 o DIST/3.3 +25 rtr taper w 0.1 hp c 0.04 n 3 lp c 0.15 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 Bureas of Mines, UC Berkely, Caltech, UC San Diego, Saint Louis University, University of Memphis, Lamont Doherty Earth Observatory, the Iris stations and the Transportable Array of EarthScope.
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: