2015/11/30 21:28:44 36.925 -97.815 5.6 3.6 Oklahoma
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution ENS 2015/11/30 21:28:44:0 36.92 -97.82 5.6 3.6 Oklahoma Stations used: GS.KAN01 GS.KAN05 GS.KAN06 GS.KAN08 GS.KAN09 GS.KAN10 GS.KAN11 GS.KAN12 GS.KAN13 GS.KAN14 GS.KAN16 GS.OK031 GS.OK032 OK.BCOK OK.CROK Filtering commands used: cut o DIST/3.3 -10 o DIST/3.3 +40 rtr taper w 0.1 hp c 0.03 n 2 lp c 0.2 n 2 Best Fitting Double Couple Mo = 1.01e+21 dyne-cm Mw = 3.27 Z = 4 km Plane Strike Dip Rake NP1 265 70 -75 NP2 47 25 -125 Principal Axes: Axis Value Plunge Azimuth T 1.01e+21 24 343 N 0.00e+00 14 80 P -1.01e+21 62 198 Moment Tensor: (dyne-cm) Component Value Mxx 5.81e+20 Mxy -2.97e+20 Mxz 7.53e+20 Myy 4.75e+19 Myz 2.40e+19 Mzz -6.28e+20 ############## ##### ############## ######## T ################# ######### ################## #################################- ###################################- ####################################-- ######################################-- ################-----------------#####-- #########------------------------------#-- ####-----------------------------------### #-------------------------------------#### --------------------------------------#### ---------------- -----------------#### ---------------- P ----------------##### --------------- ---------------##### ------------------------------###### ---------------------------####### -----------------------####### ##----------------########## ###################### ############## Global CMT Convention Moment Tensor: R T P -6.28e+20 7.53e+20 -2.40e+19 7.53e+20 5.81e+20 2.97e+20 -2.40e+19 2.97e+20 4.75e+19 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20151130212844/index.html |
STK = 265 DIP = 70 RAKE = -75 MW = 3.27 HS = 4.0
The NDK file is 20151130212844.ndk This is a marginal solution. The moment, depth and mechanism are as expected in the context of previous events. Note that the filter is 2 poles instead of 3 poles
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2015/11/30 21:28:44:0 36.92 -97.82 5.6 3.6 Oklahoma Stations used: GS.KAN01 GS.KAN05 GS.KAN06 GS.KAN08 GS.KAN09 GS.KAN10 GS.KAN11 GS.KAN12 GS.KAN13 GS.KAN14 GS.KAN16 GS.OK031 GS.OK032 OK.BCOK OK.CROK Filtering commands used: cut o DIST/3.3 -10 o DIST/3.3 +40 rtr taper w 0.1 hp c 0.03 n 2 lp c 0.2 n 2 Best Fitting Double Couple Mo = 1.01e+21 dyne-cm Mw = 3.27 Z = 4 km Plane Strike Dip Rake NP1 265 70 -75 NP2 47 25 -125 Principal Axes: Axis Value Plunge Azimuth T 1.01e+21 24 343 N 0.00e+00 14 80 P -1.01e+21 62 198 Moment Tensor: (dyne-cm) Component Value Mxx 5.81e+20 Mxy -2.97e+20 Mxz 7.53e+20 Myy 4.75e+19 Myz 2.40e+19 Mzz -6.28e+20 ############## ##### ############## ######## T ################# ######### ################## #################################- ###################################- ####################################-- ######################################-- ################-----------------#####-- #########------------------------------#-- ####-----------------------------------### #-------------------------------------#### --------------------------------------#### ---------------- -----------------#### ---------------- P ----------------##### --------------- ---------------##### ------------------------------###### ---------------------------####### -----------------------####### ##----------------########## ###################### ############## Global CMT Convention Moment Tensor: R T P -6.28e+20 7.53e+20 -2.40e+19 7.53e+20 5.81e+20 2.97e+20 -2.40e+19 2.97e+20 4.75e+19 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20151130212844/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; (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 -10 o DIST/3.3 +40 rtr taper w 0.1 hp c 0.03 n 2 lp c 0.2 n 2The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT WVFGRD96 1.0 265 85 -75 2.79 0.2669 WVFGRD96 2.0 265 85 -80 3.13 0.4480 WVFGRD96 3.0 265 80 -75 3.21 0.6570 WVFGRD96 4.0 265 70 -75 3.27 0.6654 WVFGRD96 5.0 265 70 -80 3.30 0.5952 WVFGRD96 6.0 235 45 60 3.34 0.5267 WVFGRD96 7.0 245 40 75 3.36 0.4583 WVFGRD96 8.0 240 40 75 3.46 0.3761 WVFGRD96 9.0 75 50 90 3.47 0.3142 WVFGRD96 10.0 245 40 85 3.49 0.2665 WVFGRD96 11.0 240 35 75 3.50 0.2379 WVFGRD96 12.0 230 35 60 3.51 0.2176 WVFGRD96 13.0 275 80 -60 3.50 0.2289 WVFGRD96 14.0 275 80 -60 3.53 0.2423 WVFGRD96 15.0 170 50 -65 3.64 0.2516 WVFGRD96 16.0 95 35 -75 3.58 0.2626 WVFGRD96 17.0 165 45 -70 3.67 0.2698 WVFGRD96 18.0 80 35 -80 3.61 0.2706 WVFGRD96 19.0 175 50 -65 3.68 0.2674 WVFGRD96 20.0 70 45 -95 3.63 0.2658 WVFGRD96 21.0 260 45 -85 3.63 0.2585 WVFGRD96 22.0 65 40 80 3.62 0.2523 WVFGRD96 23.0 255 50 95 3.62 0.2392 WVFGRD96 24.0 65 40 80 3.61 0.2369 WVFGRD96 25.0 65 45 90 3.63 0.2463 WVFGRD96 26.0 65 45 90 3.63 0.2549 WVFGRD96 27.0 230 45 75 3.64 0.2549 WVFGRD96 28.0 230 45 75 3.64 0.2566 WVFGRD96 29.0 235 45 80 3.64 0.2487
The best solution is
WVFGRD96 4.0 265 70 -75 3.27 0.6654
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 -10 o DIST/3.3 +40 rtr taper w 0.1 hp c 0.03 n 2 lp c 0.2 n 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 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: