The ANSS event ID is us7000mu33 and the event page is at https://earthquake.usgs.gov/earthquakes/eventpage/us7000mu33/executive.
2024/06/23 07:59:22 66.791 -140.987 10.0 3.8 Yukon, Canada
USGS/SLU Moment Tensor Solution ENS 2024/06/23 07:59:22:0 66.79 -140.99 10.0 3.8 Yukon, Canada Stations used: AK.COLD AK.DHY AK.DOT AK.E22K AK.E25K AK.E27K AK.FYU AK.GREN AK.GRES AK.HDA AK.I26K AK.I27K AK.J26L AK.K24K AK.NEA2 AK.PAX AK.PPD AK.PS04 AK.PS09 AK.RIDG AK.TOLK AK.WRH AT.MENT CN.BVCY CN.CROWY CN.DAWY IU.COLA NY.MAYO PQ.OGILY PQ.TSIIG US.EGAK 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 = 5.50e+21 dyne-cm Mw = 3.76 Z = 15 km Plane Strike Dip Rake NP1 50 65 65 NP2 278 35 132 Principal Axes: Axis Value Plunge Azimuth T 5.50e+21 62 281 N 0.00e+00 23 61 P -5.50e+21 16 158 Moment Tensor: (dyne-cm) Component Value Mxx -4.31e+21 Mxy 1.51e+21 Mxz 1.82e+21 Myy 4.96e+20 Myz -2.81e+21 Mzz 3.82e+21 -------------- ---------------------- ---------------------------- ------------------------------ -------#################---------# ----#########################----### ---################################### --################################--#### #################################----### ############ #################-------### ############ T ################---------## ############ ##############------------# ###########################--------------- ########################---------------- ######################------------------ ##################-------------------- ##############---------------------- #########------------------------- -------------------- ------- ------------------- P ------ ---------------- --- -------------- Global CMT Convention Moment Tensor: R T P 3.82e+21 1.82e+21 2.81e+21 1.82e+21 -4.31e+21 -1.51e+21 2.81e+21 -1.51e+21 4.96e+20 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20240623075922/index.html |
STK = 50 DIP = 65 RAKE = 65 MW = 3.76 HS = 15.0
The NDK file is 20240623075922.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 2024/06/23 07:59:22:0 66.79 -140.99 10.0 3.8 Yukon, Canada Stations used: AK.COLD AK.DHY AK.DOT AK.E22K AK.E25K AK.E27K AK.FYU AK.GREN AK.GRES AK.HDA AK.I26K AK.I27K AK.J26L AK.K24K AK.NEA2 AK.PAX AK.PPD AK.PS04 AK.PS09 AK.RIDG AK.TOLK AK.WRH AT.MENT CN.BVCY CN.CROWY CN.DAWY IU.COLA NY.MAYO PQ.OGILY PQ.TSIIG US.EGAK 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 = 5.50e+21 dyne-cm Mw = 3.76 Z = 15 km Plane Strike Dip Rake NP1 50 65 65 NP2 278 35 132 Principal Axes: Axis Value Plunge Azimuth T 5.50e+21 62 281 N 0.00e+00 23 61 P -5.50e+21 16 158 Moment Tensor: (dyne-cm) Component Value Mxx -4.31e+21 Mxy 1.51e+21 Mxz 1.82e+21 Myy 4.96e+20 Myz -2.81e+21 Mzz 3.82e+21 -------------- ---------------------- ---------------------------- ------------------------------ -------#################---------# ----#########################----### ---################################### --################################--#### #################################----### ############ #################-------### ############ T ################---------## ############ ##############------------# ###########################--------------- ########################---------------- ######################------------------ ##################-------------------- ##############---------------------- #########------------------------- -------------------- ------- ------------------- P ------ ---------------- --- -------------- Global CMT Convention Moment Tensor: R T P 3.82e+21 1.82e+21 2.81e+21 1.82e+21 -4.31e+21 -1.51e+21 2.81e+21 -1.51e+21 4.96e+20 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20240623075922/index.html |
Regional Moment Tensor (Mwr) Moment 4.467e+14 N-m Magnitude 3.70 Mwr Depth 17.0 km Percent DC 45% Half Duration - Catalog US Data Source US 2 Contributor US 2 Nodal Planes Plane Strike Dip Rake NP1 279 32 133 NP2 52 67 67 Principal Axes Axis Value Plunge Azimuth T 3.623e+14 61 288 N 1.368e+14 21 61 P -4.991e+14 19 159 |
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: mLg computed using the IASPEI formula. Center: mLg residuals versus epicentral distance ; the values used for the trimmed mean magnitude estimate are indicated.
Right: residuals as a function of distance and azimuth.
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 0.07 n 3The results of this grid search are as follow:
DEPTH STK DIP RAKE MW FIT WVFGRD96 1.0 90 60 -70 3.59 0.3814 WVFGRD96 2.0 50 45 65 3.65 0.3851 WVFGRD96 3.0 200 40 0 3.63 0.3869 WVFGRD96 4.0 195 40 -10 3.63 0.4081 WVFGRD96 5.0 195 45 -15 3.63 0.4265 WVFGRD96 6.0 195 45 -15 3.63 0.4421 WVFGRD96 7.0 195 50 -15 3.63 0.4555 WVFGRD96 8.0 195 50 -15 3.64 0.4679 WVFGRD96 9.0 55 65 75 3.72 0.4889 WVFGRD96 10.0 55 65 75 3.75 0.5065 WVFGRD96 11.0 55 65 75 3.75 0.5177 WVFGRD96 12.0 55 65 70 3.75 0.5253 WVFGRD96 13.0 55 65 70 3.75 0.5300 WVFGRD96 14.0 50 65 65 3.76 0.5331 WVFGRD96 15.0 50 65 65 3.76 0.5340 WVFGRD96 16.0 50 65 65 3.76 0.5332 WVFGRD96 17.0 50 65 60 3.77 0.5308 WVFGRD96 18.0 50 70 60 3.77 0.5274 WVFGRD96 19.0 50 70 55 3.78 0.5227 WVFGRD96 20.0 50 70 60 3.81 0.5211 WVFGRD96 21.0 50 70 60 3.81 0.5142 WVFGRD96 22.0 50 70 55 3.82 0.5067 WVFGRD96 23.0 50 70 55 3.82 0.4989 WVFGRD96 24.0 50 70 55 3.83 0.4902 WVFGRD96 25.0 45 75 55 3.84 0.4810 WVFGRD96 26.0 45 75 55 3.85 0.4718 WVFGRD96 27.0 45 75 50 3.85 0.4623 WVFGRD96 28.0 45 75 50 3.86 0.4524 WVFGRD96 29.0 45 75 50 3.87 0.4420
The best solution is
WVFGRD96 15.0 50 65 65 3.76 0.5340
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 0.07 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 CUS.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 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