USGS/SLU Moment Tensor Solution ENS 2022/10/06 05:18:31:0 61.28 -139.59 1.2 3.9 Alaska Stations used: AK.BARN AK.BERG AK.BMR AK.CRQ AK.DIV AK.EYAK AK.FID AK.GLB AK.GLI AK.GRNC AK.HARP AK.ISLE AK.J26L AK.K24K AK.KLU AK.L26K AK.LOGN AK.M27K AK.MCAR AK.MESA AK.PAX AK.RAG AK.RIDG AK.S31K AK.SAMH AK.SCM AK.SCRK AK.SUCK AK.TABL AK.TGL AK.VRDI AK.WAX AT.SKAG CN.DAWY CN.HYT CN.WHY NY.FARO NY.MAYO 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 0.10 n 3 Best Fitting Double Couple Mo = 2.88e+22 dyne-cm Mw = 4.24 Z = 13 km Plane Strike Dip Rake NP1 110 65 75 NP2 322 29 119 Principal Axes: Axis Value Plunge Azimuth T 2.88e+22 67 353 N 0.00e+00 14 116 P -2.88e+22 19 211 Moment Tensor: (dyne-cm) Component Value Mxx -1.45e+22 Mxy -1.20e+22 Mxz 1.79e+22 Myy -6.84e+21 Myz 3.16e+21 Mzz 2.13e+22 -------------- --#######------------- ##################---------- ######################-------- ##########################-------- #############################------- ################# ###########------- -################# T #############------ --################ ##############----- -----###############################------ -------##############################----- ---------############################----- ------------#########################----- ---------------######################--- -------------------#################---- ---------------------------#######-### ----------------------------------## ------- ----------------------## ----- P ---------------------# ---- --------------------# ---------------------- -------------- Global CMT Convention Moment Tensor: R T P 2.13e+22 1.79e+22 -3.16e+21 1.79e+22 -1.45e+22 1.20e+22 -3.16e+21 1.20e+22 -6.84e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20221006051831/index.html |
STK = 110 DIP = 65 RAKE = 75 MW = 4.24 HS = 13.0
The NDK file is 20221006051831.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2022/10/06 05:18:31:0 61.28 -139.59 1.2 3.9 Alaska Stations used: AK.BARN AK.BERG AK.BMR AK.CRQ AK.DIV AK.EYAK AK.FID AK.GLB AK.GLI AK.GRNC AK.HARP AK.ISLE AK.J26L AK.K24K AK.KLU AK.L26K AK.LOGN AK.M27K AK.MCAR AK.MESA AK.PAX AK.RAG AK.RIDG AK.S31K AK.SAMH AK.SCM AK.SCRK AK.SUCK AK.TABL AK.TGL AK.VRDI AK.WAX AT.SKAG CN.DAWY CN.HYT CN.WHY NY.FARO NY.MAYO 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 0.10 n 3 Best Fitting Double Couple Mo = 2.88e+22 dyne-cm Mw = 4.24 Z = 13 km Plane Strike Dip Rake NP1 110 65 75 NP2 322 29 119 Principal Axes: Axis Value Plunge Azimuth T 2.88e+22 67 353 N 0.00e+00 14 116 P -2.88e+22 19 211 Moment Tensor: (dyne-cm) Component Value Mxx -1.45e+22 Mxy -1.20e+22 Mxz 1.79e+22 Myy -6.84e+21 Myz 3.16e+21 Mzz 2.13e+22 -------------- --#######------------- ##################---------- ######################-------- ##########################-------- #############################------- ################# ###########------- -################# T #############------ --################ ##############----- -----###############################------ -------##############################----- ---------############################----- ------------#########################----- ---------------######################--- -------------------#################---- ---------------------------#######-### ----------------------------------## ------- ----------------------## ----- P ---------------------# ---- --------------------# ---------------------- -------------- Global CMT Convention Moment Tensor: R T P 2.13e+22 1.79e+22 -3.16e+21 1.79e+22 -1.45e+22 1.20e+22 -3.16e+21 1.20e+22 -6.84e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20221006051831/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 0.10 n 3The results of this grid search are as follow:
DEPTH STK DIP RAKE MW FIT WVFGRD96 1.0 300 35 -90 4.09 0.5282 WVFGRD96 2.0 305 25 -90 4.17 0.4500 WVFGRD96 3.0 235 35 -25 4.10 0.4366 WVFGRD96 4.0 235 35 -20 4.08 0.4653 WVFGRD96 5.0 105 75 85 4.15 0.4933 WVFGRD96 6.0 300 20 105 4.17 0.5379 WVFGRD96 7.0 105 70 80 4.17 0.5776 WVFGRD96 8.0 110 65 80 4.18 0.6084 WVFGRD96 9.0 110 65 80 4.18 0.6346 WVFGRD96 10.0 110 65 80 4.22 0.6515 WVFGRD96 11.0 110 65 75 4.23 0.6675 WVFGRD96 12.0 110 65 75 4.23 0.6766 WVFGRD96 13.0 110 65 75 4.24 0.6798 WVFGRD96 14.0 110 65 70 4.25 0.6795 WVFGRD96 15.0 110 65 70 4.25 0.6755 WVFGRD96 16.0 110 65 70 4.26 0.6686 WVFGRD96 17.0 110 65 70 4.27 0.6592 WVFGRD96 18.0 110 65 70 4.28 0.6477 WVFGRD96 19.0 105 70 70 4.29 0.6349 WVFGRD96 20.0 105 70 70 4.32 0.6201 WVFGRD96 21.0 110 70 70 4.33 0.6066 WVFGRD96 22.0 110 70 70 4.34 0.5915 WVFGRD96 23.0 110 70 70 4.34 0.5757 WVFGRD96 24.0 110 70 75 4.35 0.5588 WVFGRD96 25.0 110 70 75 4.36 0.5412 WVFGRD96 26.0 110 70 75 4.36 0.5226 WVFGRD96 27.0 110 70 75 4.37 0.5032 WVFGRD96 28.0 110 70 75 4.37 0.4833 WVFGRD96 29.0 105 75 80 4.39 0.4645
The best solution is
WVFGRD96 13.0 110 65 75 4.24 0.6798
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 0.10 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: