The ANSS event ID is us7000ga56 and the event page is at https://earthquake.usgs.gov/earthquakes/eventpage/us7000ga56/executive.
2022/01/08 08:16:42 60.390 -140.533 37.8 5.2 Yukon, Canada
USGS/SLU Moment Tensor Solution ENS 2022/01/08 08:16:42:0 60.39 -140.53 37.8 5.2 Yukon, Canada Stations used: AK.BARN AK.BMR AK.CRQ AK.CYK AK.DIV AK.EYAK AK.FID AK.GLB AK.GLI AK.GRNC AK.HARP AK.HIN AK.KAI AK.KIAG AK.KLU AK.L26K AK.LOGN AK.M26K AK.M27K AK.MCAR AK.PIN AK.PNL AK.PS12 AK.PTPK AK.RAG AK.SAMH AK.TGL AK.VMT AK.VRDI AT.SKAG AV.N25K CN.BRWY CN.BVCY CN.PLBC CN.WHY CN.YUK3 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 = 5.82e+23 dyne-cm Mw = 5.11 Z = 44 km Plane Strike Dip Rake NP1 205 79 -139 NP2 105 50 -15 Principal Axes: Axis Value Plunge Azimuth T 5.82e+23 18 329 N 0.00e+00 48 218 P -5.82e+23 36 73 Moment Tensor: (dyne-cm) Component Value Mxx 3.54e+23 Mxy -3.36e+23 Mxz 6.83e+22 Myy -2.05e+23 Myz -3.56e+23 Mzz -1.48e+23 ############## ##################---- #### #############-------- ##### T ###########----------- ####### ##########-------------- ####################---------------- ####################------------------ ####################----------- ------ ###################------------ P ------ --#################------------- ------- ---###############------------------------ ----#############------------------------- ------###########------------------------- -------########------------------------- ----------####-------------------------# ------------#----------------------### -----------######------------####### ---------######################### -------####################### ------###################### --#################### ############## Global CMT Convention Moment Tensor: R T P -1.48e+23 6.83e+22 3.56e+23 6.83e+22 3.54e+23 3.36e+23 3.56e+23 3.36e+23 -2.05e+23 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20220108081642/index.html |
STK = 105 DIP = 50 RAKE = -15 MW = 5.11 HS = 44.0
The NDK file is 20220108081642.ndk The waveform inversion is preferred.
The following compares this source inversion to those provided by others. The purpose is to look for major differences and also to note slight differences that might be inherent to the processing procedure. For completeness the USGS/SLU solution is repeated from above.
USGS/SLU Moment Tensor Solution ENS 2022/01/08 08:16:42:0 60.39 -140.53 37.8 5.2 Yukon, Canada Stations used: AK.BARN AK.BMR AK.CRQ AK.CYK AK.DIV AK.EYAK AK.FID AK.GLB AK.GLI AK.GRNC AK.HARP AK.HIN AK.KAI AK.KIAG AK.KLU AK.L26K AK.LOGN AK.M26K AK.M27K AK.MCAR AK.PIN AK.PNL AK.PS12 AK.PTPK AK.RAG AK.SAMH AK.TGL AK.VMT AK.VRDI AT.SKAG AV.N25K CN.BRWY CN.BVCY CN.PLBC CN.WHY CN.YUK3 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 = 5.82e+23 dyne-cm Mw = 5.11 Z = 44 km Plane Strike Dip Rake NP1 205 79 -139 NP2 105 50 -15 Principal Axes: Axis Value Plunge Azimuth T 5.82e+23 18 329 N 0.00e+00 48 218 P -5.82e+23 36 73 Moment Tensor: (dyne-cm) Component Value Mxx 3.54e+23 Mxy -3.36e+23 Mxz 6.83e+22 Myy -2.05e+23 Myz -3.56e+23 Mzz -1.48e+23 ############## ##################---- #### #############-------- ##### T ###########----------- ####### ##########-------------- ####################---------------- ####################------------------ ####################----------- ------ ###################------------ P ------ --#################------------- ------- ---###############------------------------ ----#############------------------------- ------###########------------------------- -------########------------------------- ----------####-------------------------# ------------#----------------------### -----------######------------####### ---------######################### -------####################### ------###################### --#################### ############## Global CMT Convention Moment Tensor: R T P -1.48e+23 6.83e+22 3.56e+23 6.83e+22 3.54e+23 3.36e+23 3.56e+23 3.36e+23 -2.05e+23 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20220108081642/index.html |
W-phase Moment Tensor (Mww) Moment 6.922e+16 N-m Magnitude 5.16 Mww Depth 30.5 km Percent DC 77% Half Duration 1.08 s Catalog US Data Source US 3 Contributor US 3 Nodal Planes Plane Strike Dip Rake NP1 208° 73° -131° NP2 99° 44° -25° Principal Axes Axis Value Plunge Azimuth T 6.456e+16 N-m 17° 327° N 0.853e+16 N-m 39° 222° P -7.309e+16 N-m 46° 76° |
Given the availability of digital waveforms for determination of the moment tensor, this section documents the added processing leading to mLg, if appropriate to the region, and ML by application of the respective IASPEI formulae. As a research study, the linear distance term of the IASPEI formula for ML is adjusted to remove a linear distance trend in residuals to give a regionally defined ML. The defined ML uses horizontal component recordings, but the same procedure is applied to the vertical components since there may be some interest in vertical component ground motions. Residual plots versus distance may indicate interesting features of ground motion scaling in some distance ranges. A residual plot of the regionalized magnitude is given as a function of distance and azimuth, since data sets may transcend different wave propagation provinces.
Left: ML computed using the IASPEI formula for Horizontal components. Center: 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.
Right: Residuals from new relation as a function of distance and azimuth.
Left: ML computed using the IASPEI formula for Vertical components (research). Center: 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.
Right: Residuals from new relation as a function of distance and azimuth.
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The focal mechanism was determined using broadband seismic waveforms. The location of the event (star) and the stations used for (red) 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's 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 are as follow:
DEPTH STK DIP RAKE MW FIT WVFGRD96 1.0 200 70 25 4.29 0.2218 WVFGRD96 2.0 215 55 45 4.45 0.2870 WVFGRD96 3.0 205 60 30 4.48 0.3011 WVFGRD96 4.0 200 80 25 4.49 0.3040 WVFGRD96 5.0 15 60 -20 4.53 0.3115 WVFGRD96 6.0 15 60 -15 4.55 0.3212 WVFGRD96 7.0 15 60 -20 4.57 0.3305 WVFGRD96 8.0 10 70 -30 4.62 0.3370 WVFGRD96 9.0 295 65 35 4.65 0.3479 WVFGRD96 10.0 295 65 35 4.67 0.3622 WVFGRD96 11.0 295 70 25 4.67 0.3749 WVFGRD96 12.0 295 70 25 4.69 0.3864 WVFGRD96 13.0 295 70 20 4.71 0.3968 WVFGRD96 14.0 110 70 20 4.72 0.4078 WVFGRD96 15.0 110 70 20 4.74 0.4211 WVFGRD96 16.0 110 70 20 4.75 0.4336 WVFGRD96 17.0 110 65 15 4.76 0.4464 WVFGRD96 18.0 110 65 15 4.78 0.4595 WVFGRD96 19.0 110 65 15 4.79 0.4719 WVFGRD96 20.0 110 65 15 4.81 0.4834 WVFGRD96 21.0 110 65 15 4.82 0.4950 WVFGRD96 22.0 105 65 10 4.84 0.5071 WVFGRD96 23.0 105 60 0 4.84 0.5192 WVFGRD96 24.0 105 60 -5 4.85 0.5324 WVFGRD96 25.0 105 60 -5 4.87 0.5463 WVFGRD96 26.0 105 60 -5 4.88 0.5608 WVFGRD96 27.0 105 60 -5 4.89 0.5741 WVFGRD96 28.0 105 60 -10 4.90 0.5886 WVFGRD96 29.0 105 60 -10 4.91 0.6012 WVFGRD96 30.0 105 60 -10 4.92 0.6133 WVFGRD96 31.0 105 55 -10 4.93 0.6236 WVFGRD96 32.0 105 55 -10 4.94 0.6356 WVFGRD96 33.0 105 55 -10 4.95 0.6452 WVFGRD96 34.0 105 55 -10 4.96 0.6535 WVFGRD96 35.0 105 55 -10 4.96 0.6598 WVFGRD96 36.0 105 55 -15 4.97 0.6653 WVFGRD96 37.0 105 55 -15 4.98 0.6688 WVFGRD96 38.0 105 55 -15 4.99 0.6725 WVFGRD96 39.0 105 55 -15 5.00 0.6736 WVFGRD96 40.0 105 45 -15 5.08 0.6747 WVFGRD96 41.0 105 50 -15 5.08 0.6781 WVFGRD96 42.0 105 50 -15 5.09 0.6826 WVFGRD96 43.0 105 50 -15 5.10 0.6837 WVFGRD96 44.0 105 50 -15 5.11 0.6846 WVFGRD96 45.0 105 50 -15 5.11 0.6839 WVFGRD96 46.0 105 50 -15 5.12 0.6824 WVFGRD96 47.0 105 50 -15 5.12 0.6805 WVFGRD96 48.0 105 50 -15 5.13 0.6767 WVFGRD96 49.0 105 50 -15 5.13 0.6738 WVFGRD96 50.0 105 50 -15 5.14 0.6693 WVFGRD96 51.0 105 50 -15 5.14 0.6657 WVFGRD96 52.0 105 50 -15 5.15 0.6604 WVFGRD96 53.0 105 50 -15 5.15 0.6554 WVFGRD96 54.0 105 50 -15 5.15 0.6504 WVFGRD96 55.0 105 50 -15 5.15 0.6445 WVFGRD96 56.0 105 50 -15 5.16 0.6393 WVFGRD96 57.0 110 50 -15 5.16 0.6339 WVFGRD96 58.0 110 50 -15 5.16 0.6296 WVFGRD96 59.0 110 50 -15 5.17 0.6242
The best solution is
WVFGRD96 44.0 105 50 -15 5.11 0.6846
The mechanism corresponding 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, the velocity model used in the predictions may not be perfect and the epicentral parameters may be be off. 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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Figure 3. Waveform comparison for selected depth. Red: observed; Blue - predicted. The time shift with respect to the model prediction is indicated. The percent of fit is also indicated. The time scale is relative to the first trace sample. |
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Focal mechanism sensitivity at the preferred depth. The red color indicates a very good fit to the waveforms. 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.
The WUS.model used for the waveform synthetic seismograms and for the surface wave eigenfunctions and dispersion is as follows (The format is in the model96 format of Computer Programs in Seismology).
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