2015/04/17 09:08:06 35.939 -97.340 6.5 3.9 Oklahoma
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution ENS 2015/04/17 09:08:06:0 35.94 -97.34 6.5 3.9 Oklahoma Stations used: GS.KAN08 GS.KAN09 GS.KAN10 GS.KS20 GS.OK025 GS.OK029 GS.OK030 GS.OK031 GS.OK032 N4.U38B N4.Z35B N4.Z38B OK.BCOK OK.CROK OK.FNO OK.OKCFA OK.U32A OK.X37A TA.ABTX TA.U40A TA.W39A US.CBKS US.KSU1 US.MIAR US.WMOK Filtering commands used: cut o DIST/3.3 -30 o DIST/3.3 +70 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.07 n 3 Best Fitting Double Couple Mo = 4.03e+21 dyne-cm Mw = 3.67 Z = 4 km Plane Strike Dip Rake NP1 115 90 -5 NP2 205 85 -180 Principal Axes: Axis Value Plunge Azimuth T 4.03e+21 4 160 N 0.00e+00 85 295 P -4.03e+21 4 70 Moment Tensor: (dyne-cm) Component Value Mxx 3.07e+21 Mxy -2.58e+21 Mxz -3.18e+20 Myy -3.07e+21 Myz -1.48e+20 Mzz 3.07e+13 ############## ###################--- #####################------- #####################--------- ######################------------ ######################-------------- -#####################-------------- ------################--------------- P ----------###########---------------- ---------------######--------------------- -------------------#---------------------- -------------------####------------------- ------------------#########--------------- -----------------#############---------- ----------------##################------ --------------#######################- ------------######################## ----------######################## --------###################### ------###################### ---############# ### ############ T Global CMT Convention Moment Tensor: R T P 3.07e+13 -3.18e+20 1.48e+20 -3.18e+20 3.07e+21 2.58e+21 1.48e+20 2.58e+21 -3.07e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20150417090806/index.html |
STK = 115 DIP = 90 RAKE = -5 MW = 3.67 HS = 4.0
The NDK file is 20150417090806.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2015/04/17 09:08:06:0 35.94 -97.34 6.5 3.9 Oklahoma Stations used: GS.KAN08 GS.KAN09 GS.KAN10 GS.KS20 GS.OK025 GS.OK029 GS.OK030 GS.OK031 GS.OK032 N4.U38B N4.Z35B N4.Z38B OK.BCOK OK.CROK OK.FNO OK.OKCFA OK.U32A OK.X37A TA.ABTX TA.U40A TA.W39A US.CBKS US.KSU1 US.MIAR US.WMOK Filtering commands used: cut o DIST/3.3 -30 o DIST/3.3 +70 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.07 n 3 Best Fitting Double Couple Mo = 4.03e+21 dyne-cm Mw = 3.67 Z = 4 km Plane Strike Dip Rake NP1 115 90 -5 NP2 205 85 -180 Principal Axes: Axis Value Plunge Azimuth T 4.03e+21 4 160 N 0.00e+00 85 295 P -4.03e+21 4 70 Moment Tensor: (dyne-cm) Component Value Mxx 3.07e+21 Mxy -2.58e+21 Mxz -3.18e+20 Myy -3.07e+21 Myz -1.48e+20 Mzz 3.07e+13 ############## ###################--- #####################------- #####################--------- ######################------------ ######################-------------- -#####################-------------- ------################--------------- P ----------###########---------------- ---------------######--------------------- -------------------#---------------------- -------------------####------------------- ------------------#########--------------- -----------------#############---------- ----------------##################------ --------------#######################- ------------######################## ----------######################## --------###################### ------###################### ---############# ### ############ T Global CMT Convention Moment Tensor: R T P 3.07e+13 -3.18e+20 1.48e+20 -3.18e+20 3.07e+21 2.58e+21 1.48e+20 2.58e+21 -3.07e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20150417090806/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 +70 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.07 n 3The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT WVFGRD96 1.0 295 90 5 3.47 0.4835 WVFGRD96 2.0 115 90 -10 3.59 0.5955 WVFGRD96 3.0 115 90 -5 3.64 0.6337 WVFGRD96 4.0 115 90 -5 3.67 0.6397 WVFGRD96 5.0 115 90 -5 3.70 0.6287 WVFGRD96 6.0 295 70 5 3.74 0.6150 WVFGRD96 7.0 295 70 5 3.76 0.6008 WVFGRD96 8.0 295 65 5 3.79 0.5835 WVFGRD96 9.0 295 65 5 3.80 0.5638 WVFGRD96 10.0 295 65 5 3.82 0.5451 WVFGRD96 11.0 295 65 5 3.83 0.5271 WVFGRD96 12.0 295 65 5 3.84 0.5100 WVFGRD96 13.0 295 65 5 3.84 0.4940 WVFGRD96 14.0 295 65 5 3.85 0.4790 WVFGRD96 15.0 295 65 5 3.86 0.4653 WVFGRD96 16.0 295 65 5 3.87 0.4528 WVFGRD96 17.0 295 65 5 3.88 0.4408 WVFGRD96 18.0 295 65 5 3.88 0.4291 WVFGRD96 19.0 295 70 5 3.88 0.4189 WVFGRD96 20.0 295 70 5 3.89 0.4098 WVFGRD96 21.0 295 65 5 3.91 0.4014 WVFGRD96 22.0 295 65 5 3.91 0.3942 WVFGRD96 23.0 295 65 5 3.92 0.3880 WVFGRD96 24.0 295 65 5 3.93 0.3835 WVFGRD96 25.0 295 65 5 3.93 0.3793 WVFGRD96 26.0 295 65 5 3.94 0.3758 WVFGRD96 27.0 210 80 20 3.89 0.3746 WVFGRD96 28.0 210 80 20 3.90 0.3784 WVFGRD96 29.0 210 80 20 3.91 0.3828
The best solution is
WVFGRD96 4.0 115 90 -5 3.67 0.6397
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 +70 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.07 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: