2014/04/20 19:07:13 35.770 -97.500 7.6 4.0 Oklahoma
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution ENS 2014/04/20 19:07:13:0 35.77 -97.50 7.6 4.0 Oklahoma Stations used: GS.OK025 GS.OK026 GS.OK027 N4.P38B N4.T35B N4.Z38B NM.UALR OK.BCOK OK.FNO OK.U32A OK.X37A TA.TUL1 TA.W39A TA.WHTX TA.X40A US.MIAR US.WMOK Filtering commands used: cut a -30 a 180 rtr taper w 0.1 hp c 0.02 n 3 lp c 0.10 n 3 br c 0.12 0.25 n 4 p 2 Best Fitting Double Couple Mo = 4.03e+21 dyne-cm Mw = 3.67 Z = 7 km Plane Strike Dip Rake NP1 105 70 -25 NP2 204 67 -158 Principal Axes: Axis Value Plunge Azimuth T 4.03e+21 2 155 N 0.00e+00 58 249 P -4.03e+21 32 64 Moment Tensor: (dyne-cm) Component Value Mxx 2.74e+21 Mxy -2.70e+21 Mxz -9.36e+20 Myy -1.64e+21 Myz -1.54e+21 Mzz -1.09e+21 ############## #################----- ##################---------- #################------------- #################----------------- #################------------------- #################------------- ----- #################-------------- P ------ -###############--------------- ------ ----############-------------------------- ------#########--------------------------- ---------#####---------------------------- -------------#---------------------------- ------------######---------------------- ------------###############---------#### ----------############################ ---------########################### --------########################## ------######################## -----################ #### --################ T # ############## Global CMT Convention Moment Tensor: R T P -1.09e+21 -9.36e+20 1.54e+21 -9.36e+20 2.74e+21 2.70e+21 1.54e+21 2.70e+21 -1.64e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140420190713/index.html |
STK = 105 DIP = 70 RAKE = -25 MW = 3.67 HS = 7.0
The NDK file is 20140420190713.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2014/04/20 19:07:13:0 35.77 -97.50 7.6 4.0 Oklahoma Stations used: GS.OK025 GS.OK026 GS.OK027 N4.P38B N4.T35B N4.Z38B NM.UALR OK.BCOK OK.FNO OK.U32A OK.X37A TA.TUL1 TA.W39A TA.WHTX TA.X40A US.MIAR US.WMOK Filtering commands used: cut a -30 a 180 rtr taper w 0.1 hp c 0.02 n 3 lp c 0.10 n 3 br c 0.12 0.25 n 4 p 2 Best Fitting Double Couple Mo = 4.03e+21 dyne-cm Mw = 3.67 Z = 7 km Plane Strike Dip Rake NP1 105 70 -25 NP2 204 67 -158 Principal Axes: Axis Value Plunge Azimuth T 4.03e+21 2 155 N 0.00e+00 58 249 P -4.03e+21 32 64 Moment Tensor: (dyne-cm) Component Value Mxx 2.74e+21 Mxy -2.70e+21 Mxz -9.36e+20 Myy -1.64e+21 Myz -1.54e+21 Mzz -1.09e+21 ############## #################----- ##################---------- #################------------- #################----------------- #################------------------- #################------------- ----- #################-------------- P ------ -###############--------------- ------ ----############-------------------------- ------#########--------------------------- ---------#####---------------------------- -------------#---------------------------- ------------######---------------------- ------------###############---------#### ----------############################ ---------########################### --------########################## ------######################## -----################ #### --################ T # ############## Global CMT Convention Moment Tensor: R T P -1.09e+21 -9.36e+20 1.54e+21 -9.36e+20 2.74e+21 2.70e+21 1.54e+21 2.70e+21 -1.64e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20140420190713/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 a -30 a 180 rtr taper w 0.1 hp c 0.02 n 3 lp c 0.10 n 3 br c 0.12 0.25 n 4 p 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 70 75 -5 3.45 0.3549 WVFGRD96 2.0 125 35 45 3.61 0.5107 WVFGRD96 3.0 115 35 25 3.67 0.5779 WVFGRD96 4.0 110 40 15 3.68 0.6131 WVFGRD96 5.0 105 75 -30 3.63 0.6290 WVFGRD96 6.0 105 70 -25 3.66 0.6419 WVFGRD96 7.0 105 70 -25 3.67 0.6421 WVFGRD96 8.0 105 70 -30 3.71 0.6272 WVFGRD96 9.0 105 70 -30 3.72 0.6170 WVFGRD96 10.0 110 75 -30 3.73 0.6054 WVFGRD96 11.0 110 75 -30 3.74 0.5948 WVFGRD96 12.0 110 75 -30 3.75 0.5822 WVFGRD96 13.0 110 70 -30 3.76 0.5719 WVFGRD96 14.0 110 70 -30 3.78 0.5607 WVFGRD96 15.0 110 70 -30 3.79 0.5500 WVFGRD96 16.0 110 65 -30 3.80 0.5391 WVFGRD96 17.0 110 65 -30 3.82 0.5275 WVFGRD96 18.0 110 65 -30 3.83 0.5169 WVFGRD96 19.0 110 65 -30 3.84 0.5046 WVFGRD96 20.0 115 65 -30 3.86 0.4921 WVFGRD96 21.0 110 60 -30 3.86 0.4786 WVFGRD96 22.0 115 60 -35 3.88 0.4666 WVFGRD96 23.0 155 85 -50 3.99 0.4657 WVFGRD96 24.0 155 85 -50 4.00 0.4606 WVFGRD96 25.0 155 80 -50 4.00 0.4551 WVFGRD96 26.0 155 80 -45 4.03 0.4514 WVFGRD96 27.0 155 80 -45 4.04 0.4470 WVFGRD96 28.0 155 75 -45 4.04 0.4426 WVFGRD96 29.0 155 75 -45 4.05 0.4414
The best solution is
WVFGRD96 7.0 105 70 -25 3.67 0.6421
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 a -30 a 180 rtr taper w 0.1 hp c 0.02 n 3 lp c 0.10 n 3 br c 0.12 0.25 n 4 p 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. |
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: