USGS/SLU Moment Tensor Solution ENS 2019/01/06 03:45:34:0 65.39 -153.35 11.5 5.0 Alaska Stations used: AK.BPAW AK.BWN AK.CAST AK.CCB AK.COLD AK.CUT AK.DHY AK.HDA AK.KTH AK.MCK AK.NEA2 AK.PPD AK.PPLA AK.RND AK.SKN AK.TRF AK.WRH IM.IL31 IU.COLA TA.D19K TA.D23K TA.E18K TA.E19K TA.E21K TA.E22K TA.E23K TA.E24K TA.F17K TA.F19K TA.F20K TA.F21K TA.F24K TA.F25K TA.G16K TA.G18K TA.G19K TA.G21K TA.G23K TA.G24K TA.H17K TA.H18K TA.H21K TA.H24K TA.I17K TA.I20K TA.I23K TA.J16K TA.J17K TA.J18K TA.J19K TA.J20K TA.J25K TA.K17K TA.K20K TA.L18K TA.L19K TA.M20K TA.M22K 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 Best Fitting Double Couple Mo = 1.74e+23 dyne-cm Mw = 4.76 Z = 13 km Plane Strike Dip Rake NP1 25 75 25 NP2 288 66 164 Principal Axes: Axis Value Plunge Azimuth T 1.74e+23 28 248 N 0.00e+00 61 54 P -1.74e+23 6 155 Moment Tensor: (dyne-cm) Component Value Mxx -1.23e+23 Mxy 1.12e+23 Mxz -1.01e+22 Myy 8.64e+22 Myz -7.49e+22 Mzz 3.67e+22 -------------- --------------------## -----------------------##### -----------------------####### -------------------------######### --------------------------########## --------------------------############ ####################-------############# #########################-############## ##########################----############ ##########################-------######### #########################-----------###### ##### ################--------------#### #### T ###############----------------## #### ##############------------------- ###################------------------- #################------------------- ##############-------------------- ###########------------------- #########------------ ---- ####-------------- P - -------------- Global CMT Convention Moment Tensor: R T P 3.67e+22 -1.01e+22 7.49e+22 -1.01e+22 -1.23e+23 -1.12e+23 7.49e+22 -1.12e+23 8.64e+22 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20190106034534/index.html |
STK = 25 DIP = 75 RAKE = 25 MW = 4.76 HS = 13.0
The NDK file is 20190106034534.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2019/01/06 03:45:34:0 65.39 -153.35 11.5 5.0 Alaska Stations used: AK.BPAW AK.BWN AK.CAST AK.CCB AK.COLD AK.CUT AK.DHY AK.HDA AK.KTH AK.MCK AK.NEA2 AK.PPD AK.PPLA AK.RND AK.SKN AK.TRF AK.WRH IM.IL31 IU.COLA TA.D19K TA.D23K TA.E18K TA.E19K TA.E21K TA.E22K TA.E23K TA.E24K TA.F17K TA.F19K TA.F20K TA.F21K TA.F24K TA.F25K TA.G16K TA.G18K TA.G19K TA.G21K TA.G23K TA.G24K TA.H17K TA.H18K TA.H21K TA.H24K TA.I17K TA.I20K TA.I23K TA.J16K TA.J17K TA.J18K TA.J19K TA.J20K TA.J25K TA.K17K TA.K20K TA.L18K TA.L19K TA.M20K TA.M22K 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 Best Fitting Double Couple Mo = 1.74e+23 dyne-cm Mw = 4.76 Z = 13 km Plane Strike Dip Rake NP1 25 75 25 NP2 288 66 164 Principal Axes: Axis Value Plunge Azimuth T 1.74e+23 28 248 N 0.00e+00 61 54 P -1.74e+23 6 155 Moment Tensor: (dyne-cm) Component Value Mxx -1.23e+23 Mxy 1.12e+23 Mxz -1.01e+22 Myy 8.64e+22 Myz -7.49e+22 Mzz 3.67e+22 -------------- --------------------## -----------------------##### -----------------------####### -------------------------######### --------------------------########## --------------------------############ ####################-------############# #########################-############## ##########################----############ ##########################-------######### #########################-----------###### ##### ################--------------#### #### T ###############----------------## #### ##############------------------- ###################------------------- #################------------------- ##############-------------------- ###########------------------- #########------------ ---- ####-------------- P - -------------- Global CMT Convention Moment Tensor: R T P 3.67e+22 -1.01e+22 7.49e+22 -1.01e+22 -1.23e+23 -1.12e+23 7.49e+22 -1.12e+23 8.64e+22 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20190106034534/index.html |
Regional Moment Tensor (Mwr) Moment 1.780e+16 N-m Magnitude 4.77 Mwr Depth 13.0 km Percent DC 54% Half Duration - Catalog US Data Source US 2 Contributor US 2 Nodal Planes Plane Strike Dip Rake NP1 294 62 -175 NP2 202 86 -28 Principal Axes Axis Value Plunge Azimuth T 1.961e+16 N-m 16 251 N -0.448e+16 N-m 62 13 P -1.513e+16 N-m 23 154 |
(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 1.0 190 55 -40 4.38 0.3323 WVFGRD96 2.0 15 55 -30 4.49 0.4261 WVFGRD96 3.0 20 55 -10 4.51 0.4500 WVFGRD96 4.0 25 70 25 4.54 0.4935 WVFGRD96 5.0 25 75 30 4.58 0.5348 WVFGRD96 6.0 25 75 30 4.61 0.5754 WVFGRD96 7.0 25 75 30 4.63 0.6132 WVFGRD96 8.0 25 75 35 4.69 0.6375 WVFGRD96 9.0 25 75 30 4.70 0.6632 WVFGRD96 10.0 25 75 30 4.72 0.6816 WVFGRD96 11.0 25 75 30 4.73 0.6934 WVFGRD96 12.0 25 75 25 4.74 0.7001 WVFGRD96 13.0 25 75 25 4.76 0.7034 WVFGRD96 14.0 20 85 25 4.77 0.7033 WVFGRD96 15.0 20 85 25 4.78 0.7012 WVFGRD96 16.0 20 85 25 4.79 0.6966 WVFGRD96 17.0 20 85 25 4.80 0.6893 WVFGRD96 18.0 20 85 25 4.81 0.6804 WVFGRD96 19.0 20 85 25 4.82 0.6692 WVFGRD96 20.0 20 85 25 4.83 0.6567 WVFGRD96 21.0 20 85 25 4.83 0.6427 WVFGRD96 22.0 20 85 25 4.84 0.6286 WVFGRD96 23.0 20 85 25 4.85 0.6130 WVFGRD96 24.0 20 85 25 4.85 0.5981 WVFGRD96 25.0 200 90 -25 4.86 0.5792 WVFGRD96 26.0 20 85 30 4.86 0.5660 WVFGRD96 27.0 20 85 30 4.87 0.5497 WVFGRD96 28.0 20 85 25 4.87 0.5337 WVFGRD96 29.0 20 85 25 4.88 0.5182
The best solution is
WVFGRD96 13.0 25 75 25 4.76 0.7034
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 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: