2011/07/30 16:08:00 62.162 -124.001 5 4.00 NWT, Canada
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution ENS 2011/07/30 16:08:00:0 62.16 -124.00 5.0 4.0 NWT, Canada Stations used: AK.BAL AK.CTG AK.DCPH AT.CRAG AT.SKAG CN.CLVN CN.FNBB CN.KUKN CN.SMPN CN.WHY CN.YKW3 CN.YUK2 CN.YUK3 CN.YUK5 CN.YUK6 CN.YUK7 US.EGAK US.WRAK Filtering commands used: hp c 0.02 n 3 lp c 0.05 n 3 Best Fitting Double Couple Mo = 1.50e+22 dyne-cm Mw = 4.05 Z = 4 km Plane Strike Dip Rake NP1 157 50 94 NP2 330 40 85 Principal Axes: Axis Value Plunge Azimuth T 1.50e+22 84 96 N 0.00e+00 3 334 P -1.50e+22 5 244 Moment Tensor: (dyne-cm) Component Value Mxx -2.94e+21 Mxy -5.94e+21 Mxz 4.29e+20 Myy -1.17e+22 Myz 2.74e+21 Mzz 1.47e+22 -------------- --#####--------------- ----###########------------- ----###############----------- ------#################----------- ------####################---------- -------#####################---------- --------#######################--------- ---------#######################-------- ----------#######################--------- ----------############# ########-------- -----------############ T #########------- -----------############ #########------- -----------#######################------ - --------######################------ P ---------#####################----- ----------####################---- -------------#################---- -------------###############-- --------------############-- --------------######## -------------- Global CMT Convention Moment Tensor: R T P 1.47e+22 4.29e+20 -2.74e+21 4.29e+20 -2.94e+21 5.94e+21 -2.74e+21 5.94e+21 -1.17e+22 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20110730160800/index.html |
STK = 330 DIP = 40 RAKE = 85 MW = 4.05 HS = 4.0
The NDK file is 20110730160800.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2011/07/30 16:08:00:0 62.16 -124.00 5.0 4.0 NWT, Canada Stations used: AK.BAL AK.CTG AK.DCPH AT.CRAG AT.SKAG CN.CLVN CN.FNBB CN.KUKN CN.SMPN CN.WHY CN.YKW3 CN.YUK2 CN.YUK3 CN.YUK5 CN.YUK6 CN.YUK7 US.EGAK US.WRAK Filtering commands used: hp c 0.02 n 3 lp c 0.05 n 3 Best Fitting Double Couple Mo = 1.50e+22 dyne-cm Mw = 4.05 Z = 4 km Plane Strike Dip Rake NP1 157 50 94 NP2 330 40 85 Principal Axes: Axis Value Plunge Azimuth T 1.50e+22 84 96 N 0.00e+00 3 334 P -1.50e+22 5 244 Moment Tensor: (dyne-cm) Component Value Mxx -2.94e+21 Mxy -5.94e+21 Mxz 4.29e+20 Myy -1.17e+22 Myz 2.74e+21 Mzz 1.47e+22 -------------- --#####--------------- ----###########------------- ----###############----------- ------#################----------- ------####################---------- -------#####################---------- --------#######################--------- ---------#######################-------- ----------#######################--------- ----------############# ########-------- -----------############ T #########------- -----------############ #########------- -----------#######################------ - --------######################------ P ---------#####################----- ----------####################---- -------------#################---- -------------###############-- --------------############-- --------------######## -------------- Global CMT Convention Moment Tensor: R T P 1.47e+22 4.29e+20 -2.74e+21 4.29e+20 -2.94e+21 5.94e+21 -2.74e+21 5.94e+21 -1.17e+22 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20110730160800/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 0.05 n 3The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT WVFGRD96 0.5 115 70 40 3.86 0.4617 WVFGRD96 1.0 295 55 25 3.89 0.4833 WVFGRD96 2.0 120 65 45 3.94 0.5203 WVFGRD96 3.0 305 50 45 3.98 0.5436 WVFGRD96 4.0 330 40 85 4.05 0.5579 WVFGRD96 5.0 325 40 75 4.08 0.5489 WVFGRD96 6.0 325 40 75 4.08 0.4980 WVFGRD96 7.0 290 70 0 4.00 0.4540 WVFGRD96 8.0 290 80 -15 4.01 0.4485 WVFGRD96 9.0 105 65 -20 3.99 0.4452 WVFGRD96 10.0 105 65 -20 4.01 0.4526 WVFGRD96 11.0 105 65 -20 4.02 0.4640 WVFGRD96 12.0 105 65 -20 4.02 0.4708 WVFGRD96 13.0 105 65 -20 4.03 0.4765 WVFGRD96 14.0 105 65 -20 4.03 0.4816 WVFGRD96 15.0 105 65 -15 4.04 0.4844 WVFGRD96 16.0 105 65 -15 4.04 0.4873 WVFGRD96 17.0 105 65 -15 4.04 0.4894 WVFGRD96 18.0 105 65 -15 4.05 0.4907 WVFGRD96 19.0 105 65 -15 4.05 0.4922 WVFGRD96 20.0 100 60 -15 4.06 0.4895 WVFGRD96 21.0 100 60 -15 4.06 0.4882 WVFGRD96 22.0 100 55 -15 4.05 0.4881 WVFGRD96 23.0 100 55 -10 4.06 0.4874 WVFGRD96 24.0 100 55 -10 4.06 0.4861 WVFGRD96 25.0 100 55 -10 4.07 0.4863 WVFGRD96 26.0 100 55 -10 4.07 0.4853 WVFGRD96 27.0 100 55 -10 4.08 0.4834 WVFGRD96 28.0 100 55 -10 4.09 0.4833 WVFGRD96 29.0 100 55 -5 4.09 0.4827
The best solution is
WVFGRD96 4.0 330 40 85 4.05 0.5579
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
hp c 0.02 n 3 lp c 0.05 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 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 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: