USGS/SLU Moment Tensor Solution ENS 2019/12/30 13:23:01:0 65.80 -150.87 7.2 3.7 Alaska Stations used: AK.BPAW AK.CCB AK.COLD AK.CUT AK.DOT AK.FYU AK.H21K AK.H24K AK.HDA AK.I21K AK.I23K AK.J19K AK.J20K AK.J25K AK.J26L AK.K20K AK.K24K AK.KTH AK.L22K AK.MCK AK.NEA2 AK.PAX AK.PPD AK.PPLA AK.SCRK AK.SKN AK.TRF AK.WRH IM.IL31 TA.D19K TA.D22K TA.D24K TA.D25K TA.E19K TA.E23K TA.E24K TA.E25K TA.F19K TA.F21K TA.F25K TA.F26K TA.G18K TA.G19K TA.G21K TA.G23K TA.G24K TA.G27K TA.H17K TA.H18K TA.J18K TA.POKR TA.TOLK Filtering commands used: cut o DIST/3.3 -40 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.08 n 3 br c 0.12 0.25 n 4 p 2 Best Fitting Double Couple Mo = 7.76e+21 dyne-cm Mw = 3.86 Z = 8 km Plane Strike Dip Rake NP1 109 85 165 NP2 200 75 5 Principal Axes: Axis Value Plunge Azimuth T 7.76e+21 14 63 N 0.00e+00 74 271 P -7.76e+21 7 155 Moment Tensor: (dyne-cm) Component Value Mxx -4.84e+21 Mxy 5.83e+21 Mxz 1.68e+21 Myy 4.50e+21 Myz 1.24e+21 Mzz 3.38e+20 -------------- ----------------###### ------------------########## -----------------############# ------------------################ ------------------############### ------------------################ T # #-----------------################# ## #####-------------###################### ##########--------######################## ###############--######################### #################---###################### ################----------################ ###############----------------######### ##############-------------------------# #############------------------------- ###########------------------------- ##########------------------------ ########---------------------- #######-------------- ---- ####-------------- P - -------------- Global CMT Convention Moment Tensor: R T P 3.38e+20 1.68e+21 -1.24e+21 1.68e+21 -4.84e+21 -5.83e+21 -1.24e+21 -5.83e+21 4.50e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20191230132301/index.html |
STK = 200 DIP = 75 RAKE = 5 MW = 3.86 HS = 8.0
The NDK file is 20191230132301.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2019/12/30 13:23:01:0 65.80 -150.87 7.2 3.7 Alaska Stations used: AK.BPAW AK.CCB AK.COLD AK.CUT AK.DOT AK.FYU AK.H21K AK.H24K AK.HDA AK.I21K AK.I23K AK.J19K AK.J20K AK.J25K AK.J26L AK.K20K AK.K24K AK.KTH AK.L22K AK.MCK AK.NEA2 AK.PAX AK.PPD AK.PPLA AK.SCRK AK.SKN AK.TRF AK.WRH IM.IL31 TA.D19K TA.D22K TA.D24K TA.D25K TA.E19K TA.E23K TA.E24K TA.E25K TA.F19K TA.F21K TA.F25K TA.F26K TA.G18K TA.G19K TA.G21K TA.G23K TA.G24K TA.G27K TA.H17K TA.H18K TA.J18K TA.POKR TA.TOLK Filtering commands used: cut o DIST/3.3 -40 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.08 n 3 br c 0.12 0.25 n 4 p 2 Best Fitting Double Couple Mo = 7.76e+21 dyne-cm Mw = 3.86 Z = 8 km Plane Strike Dip Rake NP1 109 85 165 NP2 200 75 5 Principal Axes: Axis Value Plunge Azimuth T 7.76e+21 14 63 N 0.00e+00 74 271 P -7.76e+21 7 155 Moment Tensor: (dyne-cm) Component Value Mxx -4.84e+21 Mxy 5.83e+21 Mxz 1.68e+21 Myy 4.50e+21 Myz 1.24e+21 Mzz 3.38e+20 -------------- ----------------###### ------------------########## -----------------############# ------------------################ ------------------############### ------------------################ T # #-----------------################# ## #####-------------###################### ##########--------######################## ###############--######################### #################---###################### ################----------################ ###############----------------######### ##############-------------------------# #############------------------------- ###########------------------------- ##########------------------------ ########---------------------- #######-------------- ---- ####-------------- P - -------------- Global CMT Convention Moment Tensor: R T P 3.38e+20 1.68e+21 -1.24e+21 1.68e+21 -4.84e+21 -5.83e+21 -1.24e+21 -5.83e+21 4.50e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20191230132301/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 -40 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.08 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 20 90 0 3.60 0.5612 WVFGRD96 2.0 20 90 -5 3.71 0.7484 WVFGRD96 3.0 200 85 0 3.75 0.8055 WVFGRD96 4.0 200 75 0 3.78 0.8364 WVFGRD96 5.0 200 75 0 3.80 0.8529 WVFGRD96 6.0 200 75 0 3.82 0.8612 WVFGRD96 7.0 200 75 5 3.84 0.8654 WVFGRD96 8.0 200 75 5 3.86 0.8675 WVFGRD96 9.0 200 75 5 3.87 0.8650 WVFGRD96 10.0 200 75 5 3.89 0.8609 WVFGRD96 11.0 200 75 5 3.90 0.8563 WVFGRD96 12.0 200 75 0 3.91 0.8512 WVFGRD96 13.0 200 80 10 3.92 0.8480 WVFGRD96 14.0 200 80 10 3.93 0.8438 WVFGRD96 15.0 200 80 10 3.94 0.8386 WVFGRD96 16.0 200 80 10 3.95 0.8324 WVFGRD96 17.0 200 80 10 3.96 0.8252 WVFGRD96 18.0 200 80 10 3.97 0.8169 WVFGRD96 19.0 20 80 10 3.99 0.8085 WVFGRD96 20.0 20 80 5 3.99 0.7993 WVFGRD96 21.0 20 80 5 4.00 0.7891 WVFGRD96 22.0 20 80 0 4.01 0.7786 WVFGRD96 23.0 20 80 0 4.02 0.7672 WVFGRD96 24.0 20 80 -5 4.03 0.7548 WVFGRD96 25.0 20 75 -5 4.04 0.7419 WVFGRD96 26.0 20 75 -5 4.04 0.7293 WVFGRD96 27.0 20 75 -5 4.05 0.7164 WVFGRD96 28.0 20 75 -5 4.06 0.7030 WVFGRD96 29.0 20 75 -5 4.07 0.6898
The best solution is
WVFGRD96 8.0 200 75 5 3.86 0.8675
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 -40 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.08 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. |
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 Bureau of Mines, UC Berkely, Caltech, UC San Diego, Saint Louis University, University of Memphis, Lamont Doherty Earth Observatory, the Oklahoma Geological Survey, TexNet, the Iris stations, the Transportable Array of EarthScope and other networks.
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: