USGS/SLU Moment Tensor Solution ENS 2019/05/18 09:55:36:0 36.70 -97.67 5.0 3.6 Oklahoma Stations used: GS.KAN08 GS.KAN13 N4.R32B N4.T35B N4.U38B O2.CHAN O2.DRUM O2.MRSH O2.PERK O2.PERY O2.SMNL OK.CROK OK.FNO US.CBKS US.KSU1 US.MIAR Filtering commands used: cut o DIST/3.3 -30 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.05 n 3 lp c 0.10 n 3 Best Fitting Double Couple Mo = 9.44e+20 dyne-cm Mw = 3.25 Z = 3 km Plane Strike Dip Rake NP1 345 90 -5 NP2 75 85 -180 Principal Axes: Axis Value Plunge Azimuth T 9.44e+20 4 30 N 0.00e+00 85 165 P -9.44e+20 4 300 Moment Tensor: (dyne-cm) Component Value Mxx 4.70e+20 Mxy 8.14e+20 Mxz 2.13e+19 Myy -4.70e+20 Myz 7.95e+19 Mzz 7.19e+12 --############ ------############# T ----------############ ### -----------################### -------------#################### P -------------##################### --------------##################### ------------------###################### -------------------###################-- --------------------###############------- ---------------------########------------- ---------------------#-------------------- ---------------#######-------------------- -----################------------------- ######################------------------ #####################----------------- #####################--------------- ####################-------------- ###################----------- ##################---------- ################------ ############-- Global CMT Convention Moment Tensor: R T P 7.19e+12 2.13e+19 -7.95e+19 2.13e+19 4.70e+20 -8.14e+20 -7.95e+19 -8.14e+20 -4.70e+20 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20190518095536/index.html |
STK = 345 DIP = 90 RAKE = -5 MW = 3.25 HS = 3.0
The NDK file is 20190518095536.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2019/05/18 09:55:36:0 36.70 -97.67 5.0 3.6 Oklahoma Stations used: GS.KAN08 GS.KAN13 N4.R32B N4.T35B N4.U38B O2.CHAN O2.DRUM O2.MRSH O2.PERK O2.PERY O2.SMNL OK.CROK OK.FNO US.CBKS US.KSU1 US.MIAR Filtering commands used: cut o DIST/3.3 -30 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.05 n 3 lp c 0.10 n 3 Best Fitting Double Couple Mo = 9.44e+20 dyne-cm Mw = 3.25 Z = 3 km Plane Strike Dip Rake NP1 345 90 -5 NP2 75 85 -180 Principal Axes: Axis Value Plunge Azimuth T 9.44e+20 4 30 N 0.00e+00 85 165 P -9.44e+20 4 300 Moment Tensor: (dyne-cm) Component Value Mxx 4.70e+20 Mxy 8.14e+20 Mxz 2.13e+19 Myy -4.70e+20 Myz 7.95e+19 Mzz 7.19e+12 --############ ------############# T ----------############ ### -----------################### -------------#################### P -------------##################### --------------##################### ------------------###################### -------------------###################-- --------------------###############------- ---------------------########------------- ---------------------#-------------------- ---------------#######-------------------- -----################------------------- ######################------------------ #####################----------------- #####################--------------- ####################-------------- ###################----------- ##################---------- ################------ ############-- Global CMT Convention Moment Tensor: R T P 7.19e+12 2.13e+19 -7.95e+19 2.13e+19 4.70e+20 -8.14e+20 -7.95e+19 -8.14e+20 -4.70e+20 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20190518095536/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 0.05 n 3 lp c 0.10 n 3The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT WVFGRD96 1.0 340 80 -35 3.12 0.4234 WVFGRD96 2.0 340 75 -20 3.22 0.4678 WVFGRD96 3.0 345 90 -5 3.25 0.4737 WVFGRD96 4.0 345 90 -15 3.29 0.4619 WVFGRD96 5.0 165 80 20 3.33 0.4574 WVFGRD96 6.0 165 85 35 3.38 0.4523 WVFGRD96 7.0 165 85 25 3.40 0.4480 WVFGRD96 8.0 165 80 35 3.45 0.4410 WVFGRD96 9.0 165 85 30 3.47 0.4325 WVFGRD96 10.0 165 85 30 3.49 0.4236 WVFGRD96 11.0 340 90 -30 3.50 0.4137 WVFGRD96 12.0 340 85 -30 3.52 0.4033 WVFGRD96 13.0 165 85 25 3.54 0.3919 WVFGRD96 14.0 340 85 -30 3.55 0.3790 WVFGRD96 15.0 165 85 20 3.55 0.3666 WVFGRD96 16.0 160 85 20 3.56 0.3555 WVFGRD96 17.0 345 90 25 3.58 0.3436 WVFGRD96 18.0 165 90 -25 3.59 0.3365 WVFGRD96 19.0 160 90 -25 3.59 0.3309 WVFGRD96 20.0 160 80 -15 3.59 0.3270 WVFGRD96 21.0 160 80 -15 3.59 0.3244 WVFGRD96 22.0 160 80 -20 3.61 0.3227 WVFGRD96 23.0 160 80 -20 3.61 0.3204 WVFGRD96 24.0 160 85 -20 3.62 0.3204 WVFGRD96 25.0 250 85 10 3.61 0.3195 WVFGRD96 26.0 250 85 10 3.62 0.3215 WVFGRD96 27.0 70 90 -10 3.62 0.3243 WVFGRD96 28.0 70 90 -10 3.63 0.3253 WVFGRD96 29.0 70 85 -10 3.64 0.3315
The best solution is
WVFGRD96 3.0 345 90 -5 3.25 0.4737
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 0.05 n 3 lp c 0.10 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: