USGS/SLU Moment Tensor Solution ENS 2019/07/02 18:17:07:0 66.28 -157.19 7.0 4.4 Alaska Stations used: AK.ANM AK.BPAW AK.BWN AK.CAST AK.COLD AK.KTH AK.MLY AK.NEA2 AK.RDOG TA.B20K TA.B21K TA.C18K TA.C19K TA.D20K TA.D22K TA.E18K TA.E19K TA.E21K TA.E22K TA.E23K TA.E24K TA.F15K TA.F17K TA.F19K TA.F20K TA.F21K TA.F24K TA.G16K TA.G18K TA.G19K TA.G21K TA.G23K TA.G24K TA.H17K TA.H18K TA.H19K TA.H21K TA.H23K TA.H24K TA.I20K TA.I23K TA.J16K TA.J17K TA.J18K TA.J19K TA.J20K TA.K17K TA.K20K 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 Best Fitting Double Couple Mo = 1.11e+23 dyne-cm Mw = 4.63 Z = 9 km Plane Strike Dip Rake NP1 260 85 175 NP2 350 85 5 Principal Axes: Axis Value Plunge Azimuth T 1.11e+23 7 215 N 0.00e+00 83 35 P -1.11e+23 0 305 Moment Tensor: (dyne-cm) Component Value Mxx 3.76e+22 Mxy 1.03e+23 Mxz -1.11e+22 Myy -3.93e+22 Myz -7.70e+21 Mzz 1.68e+21 ----########## --------############## ------------################ -------------################# P --------------################## --------------################### -------------------################### --------------------#################### --------------------#################### ----------------------########------------ -------------------###-------------------- ----------############-------------------- ----###################------------------- ######################------------------ ######################------------------ ######################---------------- #####################--------------- ####################-------------- ## #############------------ # T #############----------- ##############------- ###########--- Global CMT Convention Moment Tensor: R T P 1.68e+21 -1.11e+22 7.70e+21 -1.11e+22 3.76e+22 -1.03e+23 7.70e+21 -1.03e+23 -3.93e+22 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20190702181707/index.html |
STK = 350 DIP = 85 RAKE = 5 MW = 4.63 HS = 9.0
The NDK file is 20190702181707.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2019/07/02 18:17:07:0 66.28 -157.19 7.0 4.4 Alaska Stations used: AK.ANM AK.BPAW AK.BWN AK.CAST AK.COLD AK.KTH AK.MLY AK.NEA2 AK.RDOG TA.B20K TA.B21K TA.C18K TA.C19K TA.D20K TA.D22K TA.E18K TA.E19K TA.E21K TA.E22K TA.E23K TA.E24K TA.F15K TA.F17K TA.F19K TA.F20K TA.F21K TA.F24K TA.G16K TA.G18K TA.G19K TA.G21K TA.G23K TA.G24K TA.H17K TA.H18K TA.H19K TA.H21K TA.H23K TA.H24K TA.I20K TA.I23K TA.J16K TA.J17K TA.J18K TA.J19K TA.J20K TA.K17K TA.K20K 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 Best Fitting Double Couple Mo = 1.11e+23 dyne-cm Mw = 4.63 Z = 9 km Plane Strike Dip Rake NP1 260 85 175 NP2 350 85 5 Principal Axes: Axis Value Plunge Azimuth T 1.11e+23 7 215 N 0.00e+00 83 35 P -1.11e+23 0 305 Moment Tensor: (dyne-cm) Component Value Mxx 3.76e+22 Mxy 1.03e+23 Mxz -1.11e+22 Myy -3.93e+22 Myz -7.70e+21 Mzz 1.68e+21 ----########## --------############## ------------################ -------------################# P --------------################## --------------################### -------------------################### --------------------#################### --------------------#################### ----------------------########------------ -------------------###-------------------- ----------############-------------------- ----###################------------------- ######################------------------ ######################------------------ ######################---------------- #####################--------------- ####################-------------- ## #############------------ # T #############----------- ##############------- ###########--- Global CMT Convention Moment Tensor: R T P 1.68e+21 -1.11e+22 7.70e+21 -1.11e+22 3.76e+22 -1.03e+23 7.70e+21 -1.03e+23 -3.93e+22 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20190702181707/index.html |
Regional Moment Tensor (Mwr) Moment 1.271e+16 N-m Magnitude 4.67 Mwr Depth 8.0 km Percent DC 82% Half Duration - Catalog US Data Source US 2 Contributor US 2 Nodal Planes Plane Strike Dip Rake NP1 262 88 177 NP2 352 87 2 Principal Axes Axis Value Plunge Azimuth T 1.327e+16 N-m 4 217 N -0.121e+16 N-m 86 50 P -1.207e+16 N-m 1 307 |
(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 3The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT WVFGRD96 1.0 355 85 0 4.24 0.3673 WVFGRD96 2.0 350 80 -5 4.37 0.5143 WVFGRD96 3.0 350 80 -5 4.43 0.5905 WVFGRD96 4.0 350 85 -5 4.47 0.6417 WVFGRD96 5.0 350 85 -5 4.51 0.6780 WVFGRD96 6.0 170 90 0 4.54 0.7022 WVFGRD96 7.0 170 90 -5 4.58 0.7246 WVFGRD96 8.0 170 90 5 4.61 0.7453 WVFGRD96 9.0 350 85 5 4.63 0.7535 WVFGRD96 10.0 170 90 10 4.65 0.7489 WVFGRD96 11.0 350 85 5 4.67 0.7476 WVFGRD96 12.0 170 90 10 4.68 0.7403 WVFGRD96 13.0 350 85 10 4.70 0.7355 WVFGRD96 14.0 350 85 10 4.71 0.7286 WVFGRD96 15.0 350 85 10 4.72 0.7195 WVFGRD96 16.0 350 85 5 4.73 0.7094 WVFGRD96 17.0 350 85 5 4.74 0.6983 WVFGRD96 18.0 350 85 5 4.75 0.6857 WVFGRD96 19.0 350 85 5 4.76 0.6722 WVFGRD96 20.0 350 85 0 4.77 0.6586 WVFGRD96 21.0 350 80 5 4.77 0.6448 WVFGRD96 22.0 350 80 5 4.78 0.6300 WVFGRD96 23.0 350 80 5 4.79 0.6152 WVFGRD96 24.0 350 80 5 4.79 0.6003 WVFGRD96 25.0 350 80 5 4.80 0.5854 WVFGRD96 26.0 350 80 0 4.80 0.5702 WVFGRD96 27.0 350 80 0 4.80 0.5552 WVFGRD96 28.0 350 80 0 4.81 0.5404 WVFGRD96 29.0 170 90 10 4.81 0.5281
The best solution is
WVFGRD96 9.0 350 85 5 4.63 0.7535
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
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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: