USGS/SLU Moment Tensor Solution ENS 2016/06/25 10:30:36:0 36.51 -99.01 7.3 3.7 Oklahoma Stations used: GS.KAN06 GS.KAN12 GS.KAN16 GS.OK032 GS.OK035 GS.OK038 GS.OK040 GS.OK043 OK.NOKA Filtering commands used: cut o DIST/3.3 -20 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.04 n 3 lp c 0.10 n 3 Best Fitting Double Couple Mo = 1.58e+21 dyne-cm Mw = 3.40 Z = 4 km Plane Strike Dip Rake NP1 243 50 -94 NP2 70 40 -85 Principal Axes: Axis Value Plunge Azimuth T 1.58e+21 5 336 N 0.00e+00 3 246 P -1.58e+21 84 124 Moment Tensor: (dyne-cm) Component Value Mxx 1.32e+21 Mxy -5.68e+20 Mxz 2.21e+20 Myy 2.39e+20 Myz -1.93e+20 Mzz -1.55e+21 ############## # T ################## #### ##################### ############################## ########################---####### ################-------------------# #############------------------------- ###########----------------------------# #########------------------------------# ########--------------------------------## #######-------------- ---------------### #####---------------- P --------------#### ####----------------- -------------##### ##---------------------------------##### ##-------------------------------####### ------------------------------######## ##------------------------########## #####---------------############## ############################## ############################ ###################### ############## Global CMT Convention Moment Tensor: R T P -1.55e+21 2.21e+20 1.93e+20 2.21e+20 1.32e+21 5.68e+20 1.93e+20 5.68e+20 2.39e+20 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20160625103036/index.html |
STK = 70 DIP = 40 RAKE = -85 MW = 3.40 HS = 4.0
The NDK file is 20160625103036.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2016/06/25 10:30:36:0 36.51 -99.01 7.3 3.7 Oklahoma Stations used: GS.KAN06 GS.KAN12 GS.KAN16 GS.OK032 GS.OK035 GS.OK038 GS.OK040 GS.OK043 OK.NOKA Filtering commands used: cut o DIST/3.3 -20 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.04 n 3 lp c 0.10 n 3 Best Fitting Double Couple Mo = 1.58e+21 dyne-cm Mw = 3.40 Z = 4 km Plane Strike Dip Rake NP1 243 50 -94 NP2 70 40 -85 Principal Axes: Axis Value Plunge Azimuth T 1.58e+21 5 336 N 0.00e+00 3 246 P -1.58e+21 84 124 Moment Tensor: (dyne-cm) Component Value Mxx 1.32e+21 Mxy -5.68e+20 Mxz 2.21e+20 Myy 2.39e+20 Myz -1.93e+20 Mzz -1.55e+21 ############## # T ################## #### ##################### ############################## ########################---####### ################-------------------# #############------------------------- ###########----------------------------# #########------------------------------# ########--------------------------------## #######-------------- ---------------### #####---------------- P --------------#### ####----------------- -------------##### ##---------------------------------##### ##-------------------------------####### ------------------------------######## ##------------------------########## #####---------------############## ############################## ############################ ###################### ############## Global CMT Convention Moment Tensor: R T P -1.55e+21 2.21e+20 1.93e+20 2.21e+20 1.32e+21 5.68e+20 1.93e+20 5.68e+20 2.39e+20 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20160625103036/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 -20 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.04 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 1.0 285 55 -20 3.04 0.3821 WVFGRD96 2.0 280 50 -30 3.23 0.4783 WVFGRD96 3.0 280 55 -35 3.27 0.5136 WVFGRD96 4.0 70 40 -85 3.40 0.5171 WVFGRD96 5.0 85 50 -65 3.39 0.4971 WVFGRD96 6.0 100 65 -35 3.35 0.4670 WVFGRD96 7.0 295 80 30 3.35 0.4457 WVFGRD96 8.0 85 50 -65 3.48 0.4336 WVFGRD96 9.0 290 80 30 3.41 0.4076 WVFGRD96 10.0 290 80 25 3.42 0.3954 WVFGRD96 11.0 290 85 20 3.43 0.3819 WVFGRD96 12.0 290 85 20 3.44 0.3692 WVFGRD96 13.0 290 90 15 3.45 0.3604 WVFGRD96 14.0 110 85 -15 3.47 0.3532 WVFGRD96 15.0 110 85 -15 3.49 0.3461 WVFGRD96 16.0 110 90 -15 3.49 0.3414 WVFGRD96 17.0 290 90 15 3.51 0.3366 WVFGRD96 18.0 290 85 15 3.51 0.3336 WVFGRD96 19.0 110 90 -10 3.52 0.3307 WVFGRD96 20.0 285 85 15 3.54 0.3280 WVFGRD96 21.0 110 90 -10 3.55 0.3263 WVFGRD96 22.0 110 90 -10 3.56 0.3238 WVFGRD96 23.0 285 80 15 3.57 0.3205 WVFGRD96 24.0 285 80 15 3.58 0.3161 WVFGRD96 25.0 285 80 15 3.59 0.3100 WVFGRD96 26.0 285 80 10 3.58 0.3067 WVFGRD96 27.0 285 80 10 3.59 0.3032 WVFGRD96 28.0 285 80 10 3.60 0.3004 WVFGRD96 29.0 250 85 70 3.70 0.3029
The best solution is
WVFGRD96 4.0 70 40 -85 3.40 0.5171
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 -20 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.04 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: