USGS/SLU Moment Tensor Solution ENS 2019/10/18 00:58:28:0 66.29 -157.27 9.5 5.3 Alaska Stations used: AK.ANM AK.BPAW AK.BWN AK.COLD AK.H21K AK.H23K AK.H24K AK.I23K AK.J17K AK.J19K AK.J20K AK.K20K AK.KTH AK.MLY AK.NEA2 AK.RDOG TA.B21K TA.C18K TA.C19K TA.D19K TA.D20K TA.D22K TA.D23K TA.E18K TA.E19K TA.E22K TA.E23K TA.E24K TA.F15K TA.F17K TA.F19K TA.F20K TA.F21K TA.F24K TA.G16K TA.G18K TA.G21K TA.G23K TA.G24K TA.H17K TA.H18K TA.H19K TA.I20K TA.I21K TA.J18K TA.K17K 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 0.10 n 3 Best Fitting Double Couple Mo = 1.05e+24 dyne-cm Mw = 5.28 Z = 10 km Plane Strike Dip Rake NP1 77 80 -170 NP2 345 80 -10 Principal Axes: Axis Value Plunge Azimuth T 1.05e+24 0 211 N 0.00e+00 76 120 P -1.05e+24 14 301 Moment Tensor: (dyne-cm) Component Value Mxx 5.12e+23 Mxy 8.95e+23 Mxz -1.29e+23 Myy -4.50e+23 Myz 2.11e+23 Mzz -6.22e+22 --############ -------############### -----------################# -------------################# -------------################## - P -------------################### -- --------------################### ---------------------################### ---------------------################### -----------------------###############---- -----------------------##########--------- ------------------------###--------------- --------------------####------------------ --------################---------------- ########################---------------- #######################--------------- #######################------------- ######################------------ ####################---------- ## ##############--------- T ##############------ ############-- Global CMT Convention Moment Tensor: R T P -6.22e+22 -1.29e+23 -2.11e+23 -1.29e+23 5.12e+23 -8.95e+23 -2.11e+23 -8.95e+23 -4.50e+23 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20191018005828/index.html |
STK = 345 DIP = 80 RAKE = -10 MW = 5.28 HS = 10.0
The NDK file is 20191018005828.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2019/10/18 00:58:28:0 66.29 -157.27 9.5 5.3 Alaska Stations used: AK.ANM AK.BPAW AK.BWN AK.COLD AK.H21K AK.H23K AK.H24K AK.I23K AK.J17K AK.J19K AK.J20K AK.K20K AK.KTH AK.MLY AK.NEA2 AK.RDOG TA.B21K TA.C18K TA.C19K TA.D19K TA.D20K TA.D22K TA.D23K TA.E18K TA.E19K TA.E22K TA.E23K TA.E24K TA.F15K TA.F17K TA.F19K TA.F20K TA.F21K TA.F24K TA.G16K TA.G18K TA.G21K TA.G23K TA.G24K TA.H17K TA.H18K TA.H19K TA.I20K TA.I21K TA.J18K TA.K17K 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 0.10 n 3 Best Fitting Double Couple Mo = 1.05e+24 dyne-cm Mw = 5.28 Z = 10 km Plane Strike Dip Rake NP1 77 80 -170 NP2 345 80 -10 Principal Axes: Axis Value Plunge Azimuth T 1.05e+24 0 211 N 0.00e+00 76 120 P -1.05e+24 14 301 Moment Tensor: (dyne-cm) Component Value Mxx 5.12e+23 Mxy 8.95e+23 Mxz -1.29e+23 Myy -4.50e+23 Myz 2.11e+23 Mzz -6.22e+22 --############ -------############### -----------################# -------------################# -------------################## - P -------------################### -- --------------################### ---------------------################### ---------------------################### -----------------------###############---- -----------------------##########--------- ------------------------###--------------- --------------------####------------------ --------################---------------- ########################---------------- #######################--------------- #######################------------- ######################------------ ####################---------- ## ##############--------- T ##############------ ############-- Global CMT Convention Moment Tensor: R T P -6.22e+22 -1.29e+23 -2.11e+23 -1.29e+23 5.12e+23 -8.95e+23 -2.11e+23 -8.95e+23 -4.50e+23 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20191018005828/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 0.10 n 3The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT WVFGRD96 1.0 170 75 10 4.81 0.2765 WVFGRD96 2.0 170 75 15 4.96 0.3951 WVFGRD96 3.0 165 80 -5 5.01 0.4544 WVFGRD96 4.0 165 75 -15 5.07 0.5034 WVFGRD96 5.0 165 75 -15 5.11 0.5424 WVFGRD96 6.0 345 75 -10 5.15 0.5753 WVFGRD96 7.0 345 80 -10 5.18 0.6057 WVFGRD96 8.0 345 75 -15 5.23 0.6361 WVFGRD96 9.0 345 80 -10 5.26 0.6503 WVFGRD96 10.0 345 80 -10 5.28 0.6580 WVFGRD96 11.0 165 85 10 5.30 0.6550 WVFGRD96 12.0 345 80 -10 5.32 0.6572 WVFGRD96 13.0 345 80 -5 5.33 0.6534 WVFGRD96 14.0 345 80 -5 5.35 0.6474 WVFGRD96 15.0 345 80 5 5.36 0.6406 WVFGRD96 16.0 345 80 5 5.37 0.6316 WVFGRD96 17.0 345 80 5 5.38 0.6205 WVFGRD96 18.0 345 80 10 5.39 0.6082 WVFGRD96 19.0 345 80 10 5.40 0.5953 WVFGRD96 20.0 345 80 10 5.41 0.5811 WVFGRD96 21.0 345 80 10 5.42 0.5673 WVFGRD96 22.0 345 80 10 5.42 0.5531 WVFGRD96 23.0 345 80 10 5.43 0.5385 WVFGRD96 24.0 345 75 10 5.43 0.5251 WVFGRD96 25.0 345 75 10 5.44 0.5115 WVFGRD96 26.0 345 75 10 5.44 0.4977 WVFGRD96 27.0 345 75 10 5.44 0.4839 WVFGRD96 28.0 345 75 10 5.44 0.4710 WVFGRD96 29.0 345 75 10 5.44 0.4580
The best solution is
WVFGRD96 10.0 345 80 -10 5.28 0.6580
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 0.10 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 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: