USGS/SLU Moment Tensor Solution ENS 2020/12/21 12:16:18:0 66.34 -135.70 21.5 4.3 Yukon, Canada Stations used: AK.G27K AK.I27K CN.INK TA.E29M TA.EPYK TA.G30M TA.G31M TA.H27K TA.H29M TA.H31M TA.I28M TA.I29M TA.I30M TA.J29N TA.J30M TA.K29M 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 0.07 n 3 Best Fitting Double Couple Mo = 2.79e+22 dyne-cm Mw = 4.23 Z = 34 km Plane Strike Dip Rake NP1 80 90 10 NP2 350 80 180 Principal Axes: Axis Value Plunge Azimuth T 2.79e+22 7 305 N 0.00e+00 80 80 P -2.79e+22 7 215 Moment Tensor: (dyne-cm) Component Value Mxx -9.38e+21 Mxy -2.58e+22 Mxz 4.76e+21 Myy 9.38e+21 Myz -8.40e+20 Mzz -4.23e+14 ####---------- #########------------- #############--------------- #############---------------- T ##############----------------- # ##############------------------ ####################------------------ #####################------------------- ######################------------------ #######################--------------##### #######################---################ ################--------################## #####-------------------################## -----------------------################# ------------------------################ -----------------------############### ----------------------############## ---------------------############# -- --------------########### - P --------------########## --------------####### -----------### Global CMT Convention Moment Tensor: R T P -4.23e+14 4.76e+21 8.40e+20 4.76e+21 -9.38e+21 2.58e+22 8.40e+20 2.58e+22 9.38e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20201221121618/index.html |
STK = 80 DIP = 90 RAKE = 10 MW = 4.23 HS = 34.0
The NDK file is 20201221121618.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2020/12/21 12:16:18:0 66.34 -135.70 21.5 4.3 Yukon, Canada Stations used: AK.G27K AK.I27K CN.INK TA.E29M TA.EPYK TA.G30M TA.G31M TA.H27K TA.H29M TA.H31M TA.I28M TA.I29M TA.I30M TA.J29N TA.J30M TA.K29M 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 0.07 n 3 Best Fitting Double Couple Mo = 2.79e+22 dyne-cm Mw = 4.23 Z = 34 km Plane Strike Dip Rake NP1 80 90 10 NP2 350 80 180 Principal Axes: Axis Value Plunge Azimuth T 2.79e+22 7 305 N 0.00e+00 80 80 P -2.79e+22 7 215 Moment Tensor: (dyne-cm) Component Value Mxx -9.38e+21 Mxy -2.58e+22 Mxz 4.76e+21 Myy 9.38e+21 Myz -8.40e+20 Mzz -4.23e+14 ####---------- #########------------- #############--------------- #############---------------- T ##############----------------- # ##############------------------ ####################------------------ #####################------------------- ######################------------------ #######################--------------##### #######################---################ ################--------################## #####-------------------################## -----------------------################# ------------------------################ -----------------------############### ----------------------############## ---------------------############# -- --------------########### - P --------------########## --------------####### -----------### Global CMT Convention Moment Tensor: R T P -4.23e+14 4.76e+21 8.40e+20 4.76e+21 -9.38e+21 2.58e+22 8.40e+20 2.58e+22 9.38e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20201221121618/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 0.07 n 3The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT WVFGRD96 1.0 255 75 -5 3.90 0.5538 WVFGRD96 2.0 255 90 5 3.92 0.5913 WVFGRD96 3.0 255 90 10 3.95 0.6081 WVFGRD96 4.0 75 90 15 3.97 0.6187 WVFGRD96 5.0 255 85 -15 3.98 0.6367 WVFGRD96 6.0 75 90 15 3.99 0.6461 WVFGRD96 7.0 75 90 15 4.00 0.6563 WVFGRD96 8.0 255 85 -15 4.01 0.6677 WVFGRD96 9.0 255 85 -15 4.02 0.6749 WVFGRD96 10.0 75 90 15 4.03 0.6808 WVFGRD96 11.0 75 90 15 4.04 0.6870 WVFGRD96 12.0 75 90 15 4.05 0.6938 WVFGRD96 13.0 75 90 10 4.05 0.7006 WVFGRD96 14.0 75 90 10 4.06 0.7075 WVFGRD96 15.0 255 90 -10 4.07 0.7138 WVFGRD96 16.0 255 90 -10 4.08 0.7204 WVFGRD96 17.0 75 90 10 4.08 0.7270 WVFGRD96 18.0 75 90 10 4.09 0.7328 WVFGRD96 19.0 75 90 10 4.10 0.7393 WVFGRD96 20.0 255 90 -10 4.11 0.7472 WVFGRD96 21.0 75 90 10 4.12 0.7535 WVFGRD96 22.0 260 90 -10 4.13 0.7595 WVFGRD96 23.0 80 90 10 4.14 0.7660 WVFGRD96 24.0 260 90 -10 4.15 0.7716 WVFGRD96 25.0 260 90 -10 4.15 0.7764 WVFGRD96 26.0 80 90 10 4.16 0.7810 WVFGRD96 27.0 260 90 -10 4.17 0.7853 WVFGRD96 28.0 260 90 -10 4.18 0.7903 WVFGRD96 29.0 80 90 10 4.19 0.7946 WVFGRD96 30.0 80 90 10 4.19 0.7971 WVFGRD96 31.0 80 90 10 4.20 0.7993 WVFGRD96 32.0 260 90 -10 4.21 0.8013 WVFGRD96 33.0 80 90 10 4.22 0.8023 WVFGRD96 34.0 80 90 10 4.23 0.8036 WVFGRD96 35.0 80 90 10 4.24 0.8031 WVFGRD96 36.0 260 85 -10 4.25 0.8029 WVFGRD96 37.0 80 90 10 4.27 0.8017 WVFGRD96 38.0 80 90 10 4.28 0.8001 WVFGRD96 39.0 260 90 -10 4.30 0.7977 WVFGRD96 40.0 260 90 -10 4.32 0.7948 WVFGRD96 41.0 80 90 10 4.33 0.7910 WVFGRD96 42.0 80 90 10 4.34 0.7882 WVFGRD96 43.0 80 90 10 4.34 0.7839 WVFGRD96 44.0 80 90 10 4.35 0.7788 WVFGRD96 45.0 80 90 10 4.36 0.7728 WVFGRD96 46.0 80 90 10 4.37 0.7665 WVFGRD96 47.0 80 90 10 4.37 0.7614 WVFGRD96 48.0 260 90 -10 4.38 0.7555 WVFGRD96 49.0 260 90 -10 4.39 0.7487 WVFGRD96 50.0 80 90 10 4.39 0.7421
The best solution is
WVFGRD96 34.0 80 90 10 4.23 0.8036
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 0.07 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 CUS.model used for the waveform synthetic seismograms and for the surface wave eigenfunctions and dispersion is as follows:
MODEL.01 CUS Model with Q from simple gamma values 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 1.0000 5.0000 2.8900 2.5000 0.172E-02 0.387E-02 0.00 0.00 1.00 1.00 9.0000 6.1000 3.5200 2.7300 0.160E-02 0.363E-02 0.00 0.00 1.00 1.00 10.0000 6.4000 3.7000 2.8200 0.149E-02 0.336E-02 0.00 0.00 1.00 1.00 20.0000 6.7000 3.8700 2.9020 0.000E-04 0.000E-04 0.00 0.00 1.00 1.00 0.0000 8.1500 4.7000 3.3640 0.194E-02 0.431E-02 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: