2012/09/01 10:57:34 66.882 -135.983 10.1 4.40 Yukon, Canada
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution ENS 2012/09/01 10:57:34:5 66.88 -135.98 10.1 4.4 Yukon, Canada Stations used: AK.BPAW AK.CAST AK.CCB AK.COLD AK.DHY AK.DIV AK.DOT AK.FYU AK.GHO AK.GLM AK.HDA CN.BVCY CN.CLVN CN.DAWY CN.INK IU.COLA US.EGAK Filtering commands used: hp c 0.02 n 3 lp c 0.06 n 3 br c 0.12 0.25 n 4 p 2 Best Fitting Double Couple Mo = 8.32e+21 dyne-cm Mw = 3.88 Z = 26 km Plane Strike Dip Rake NP1 359 82 145 NP2 95 55 10 Principal Axes: Axis Value Plunge Azimuth T 8.32e+21 30 311 N 0.00e+00 54 168 P -8.32e+21 18 52 Moment Tensor: (dyne-cm) Component Value Mxx -1.82e+20 Mxy -6.73e+21 Mxz 9.02e+20 Myy -1.18e+21 Myz -4.64e+21 Mzz 1.36e+21 #######------- ############---------- ###############------------- ################-------------- ##### ##########----------- -- ###### T ###########---------- P --- ####### ###########---------- ---- ######################------------------ ######################------------------ #######################------------------- -######################------------------- --#####################------------------- ----###################------------------# ------################----------------## ----------############------------###### ---------------######-------########## --------------------################ -------------------############### -----------------############# ---------------############# ------------########## --------###### Global CMT Convention Moment Tensor: R T P 1.36e+21 9.02e+20 4.64e+21 9.02e+20 -1.82e+20 6.73e+21 4.64e+21 6.73e+21 -1.18e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20120901105734/index.html |
STK = 95 DIP = 55 RAKE = 10 MW = 3.88 HS = 26.0
The NDK file is 20120901105734.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2012/09/01 10:57:34:5 66.88 -135.98 10.1 4.4 Yukon, Canada Stations used: AK.BPAW AK.CAST AK.CCB AK.COLD AK.DHY AK.DIV AK.DOT AK.FYU AK.GHO AK.GLM AK.HDA CN.BVCY CN.CLVN CN.DAWY CN.INK IU.COLA US.EGAK Filtering commands used: hp c 0.02 n 3 lp c 0.06 n 3 br c 0.12 0.25 n 4 p 2 Best Fitting Double Couple Mo = 8.32e+21 dyne-cm Mw = 3.88 Z = 26 km Plane Strike Dip Rake NP1 359 82 145 NP2 95 55 10 Principal Axes: Axis Value Plunge Azimuth T 8.32e+21 30 311 N 0.00e+00 54 168 P -8.32e+21 18 52 Moment Tensor: (dyne-cm) Component Value Mxx -1.82e+20 Mxy -6.73e+21 Mxz 9.02e+20 Myy -1.18e+21 Myz -4.64e+21 Mzz 1.36e+21 #######------- ############---------- ###############------------- ################-------------- ##### ##########----------- -- ###### T ###########---------- P --- ####### ###########---------- ---- ######################------------------ ######################------------------ #######################------------------- -######################------------------- --#####################------------------- ----###################------------------# ------################----------------## ----------############------------###### ---------------######-------########## --------------------################ -------------------############### -----------------############# ---------------############# ------------########## --------###### Global CMT Convention Moment Tensor: R T P 1.36e+21 9.02e+20 4.64e+21 9.02e+20 -1.82e+20 6.73e+21 4.64e+21 6.73e+21 -1.18e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20120901105734/index.html |
(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:
hp c 0.02 n 3 lp c 0.06 n 3 br c 0.12 0.25 n 4 p 2The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT WVFGRD96 0.5 230 50 -90 3.71 0.3249 WVFGRD96 1.0 180 50 -80 3.53 0.3144 WVFGRD96 2.0 -5 40 -90 3.59 0.3351 WVFGRD96 3.0 180 50 -80 3.66 0.3294 WVFGRD96 4.0 300 40 45 3.68 0.3125 WVFGRD96 5.0 290 40 35 3.72 0.3109 WVFGRD96 6.0 270 50 0 3.72 0.3136 WVFGRD96 7.0 265 45 -20 3.72 0.3192 WVFGRD96 8.0 260 40 -30 3.79 0.3262 WVFGRD96 9.0 260 40 -35 3.79 0.3358 WVFGRD96 10.0 260 40 -35 3.78 0.3441 WVFGRD96 11.0 260 45 -40 3.78 0.3525 WVFGRD96 12.0 260 40 -40 3.78 0.3596 WVFGRD96 13.0 265 45 -35 3.78 0.3657 WVFGRD96 14.0 265 45 -35 3.78 0.3713 WVFGRD96 15.0 90 50 -10 3.78 0.3756 WVFGRD96 16.0 100 45 20 3.78 0.3846 WVFGRD96 17.0 100 45 20 3.79 0.3951 WVFGRD96 18.0 100 45 20 3.79 0.4041 WVFGRD96 19.0 100 50 20 3.82 0.4121 WVFGRD96 20.0 100 50 20 3.82 0.4189 WVFGRD96 21.0 100 50 20 3.83 0.4239 WVFGRD96 22.0 100 50 15 3.84 0.4283 WVFGRD96 23.0 100 50 15 3.85 0.4318 WVFGRD96 24.0 95 55 10 3.87 0.4341 WVFGRD96 25.0 95 55 10 3.88 0.4357 WVFGRD96 26.0 95 55 10 3.88 0.4362 WVFGRD96 27.0 95 55 5 3.90 0.4361 WVFGRD96 28.0 95 55 5 3.90 0.4354 WVFGRD96 29.0 95 55 5 3.91 0.4338 WVFGRD96 30.0 95 55 5 3.92 0.4316 WVFGRD96 31.0 95 55 5 3.93 0.4287 WVFGRD96 32.0 95 55 5 3.93 0.4251 WVFGRD96 33.0 95 55 5 3.94 0.4209 WVFGRD96 34.0 95 60 5 3.97 0.4165 WVFGRD96 35.0 95 60 5 3.98 0.4116 WVFGRD96 36.0 310 60 30 3.96 0.4041 WVFGRD96 37.0 305 60 30 3.97 0.3987 WVFGRD96 38.0 305 60 30 3.99 0.3925 WVFGRD96 39.0 90 60 5 4.01 0.3855 WVFGRD96 40.0 95 45 10 4.07 0.3798 WVFGRD96 41.0 95 45 10 4.07 0.3733 WVFGRD96 42.0 100 45 15 4.08 0.3664 WVFGRD96 43.0 100 45 15 4.08 0.3593 WVFGRD96 44.0 95 50 10 4.10 0.3520 WVFGRD96 45.0 95 50 10 4.10 0.3443 WVFGRD96 46.0 95 50 10 4.11 0.3363 WVFGRD96 47.0 100 50 15 4.11 0.3283 WVFGRD96 48.0 100 50 15 4.12 0.3202 WVFGRD96 49.0 100 50 15 4.12 0.3118
The best solution is
WVFGRD96 26.0 95 55 10 3.88 0.4362
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 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
hp c 0.02 n 3 lp c 0.06 n 3 br c 0.12 0.25 n 4 p 2
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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: