2012/08/29 12:50:55 60.314 -150.712 58.7 4.40 Alaska
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution ENS 2012/08/29 12:50:55:0 60.31 -150.71 58.7 4.4 Alaska Stations used: AK.BMR AK.BPAW AK.BRLK AK.CNP AK.DOT AK.FIB AK.FID AK.GHO AK.GLI AK.HIN AK.HOM AK.KNK AK.KTH AK.RC01 AK.RIDG AK.SAW AK.SCM AK.SKN AK.SSN AT.SVW2 II.KDAK IU.COLA Filtering commands used: hp c 0.02 n 3 lp c 0.06 n 3 Best Fitting Double Couple Mo = 7.85e+22 dyne-cm Mw = 4.53 Z = 72 km Plane Strike Dip Rake NP1 281 72 154 NP2 20 65 20 Principal Axes: Axis Value Plunge Azimuth T 7.85e+22 31 239 N 0.00e+00 58 69 P -7.85e+22 5 332 Moment Tensor: (dyne-cm) Component Value Mxx -4.54e+22 Mxy 5.78e+22 Mxz -2.34e+22 Myy 2.48e+22 Myz -2.69e+22 Mzz 2.06e+22 -------------- P ----------------### --- ----------------###### -----------------------####### --------------------------######## ---------------------------######### ---------------------------########### ----------------------------############ -###################--------############ ############################-############# ############################------######## ###########################----------##### ###########################-------------## ###### ################--------------- ###### T ###############---------------- ##### ##############---------------- ####################---------------- ##################---------------- ###############--------------- ############---------------- #######--------------- -------------- Global CMT Convention Moment Tensor: R T P 2.06e+22 -2.34e+22 2.69e+22 -2.34e+22 -4.54e+22 -5.78e+22 2.69e+22 -5.78e+22 2.48e+22 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20120829125055/index.html |
STK = 20 DIP = 65 RAKE = 20 MW = 4.53 HS = 72.0
The NDK file is 20120829125055.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2012/08/29 12:50:55:0 60.31 -150.71 58.7 4.4 Alaska Stations used: AK.BMR AK.BPAW AK.BRLK AK.CNP AK.DOT AK.FIB AK.FID AK.GHO AK.GLI AK.HIN AK.HOM AK.KNK AK.KTH AK.RC01 AK.RIDG AK.SAW AK.SCM AK.SKN AK.SSN AT.SVW2 II.KDAK IU.COLA Filtering commands used: hp c 0.02 n 3 lp c 0.06 n 3 Best Fitting Double Couple Mo = 7.85e+22 dyne-cm Mw = 4.53 Z = 72 km Plane Strike Dip Rake NP1 281 72 154 NP2 20 65 20 Principal Axes: Axis Value Plunge Azimuth T 7.85e+22 31 239 N 0.00e+00 58 69 P -7.85e+22 5 332 Moment Tensor: (dyne-cm) Component Value Mxx -4.54e+22 Mxy 5.78e+22 Mxz -2.34e+22 Myy 2.48e+22 Myz -2.69e+22 Mzz 2.06e+22 -------------- P ----------------### --- ----------------###### -----------------------####### --------------------------######## ---------------------------######### ---------------------------########### ----------------------------############ -###################--------############ ############################-############# ############################------######## ###########################----------##### ###########################-------------## ###### ################--------------- ###### T ###############---------------- ##### ##############---------------- ####################---------------- ##################---------------- ###############--------------- ############---------------- #######--------------- -------------- Global CMT Convention Moment Tensor: R T P 2.06e+22 -2.34e+22 2.69e+22 -2.34e+22 -4.54e+22 -5.78e+22 2.69e+22 -5.78e+22 2.48e+22 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20120829125055/index.html |
USGS/SLU Regional Moment Solution 12/08/29 12:50:51.00 Epicenter: 60.269 -150.709 MW 4.5 USGS/SLU REGIONAL MOMENT TENSOR Depth 67 No. of sta: 53 Moment Tensor; Scale 10**15 Nm Mrr= 1.50 Mtt=-3.34 Mpp= 1.84 Mrt=-2.69 Mrp= 3.18 Mtp=-4.53 Principal axes: T Val= 7.36 Plg=35 Azm=238 N -1.30 54 72 P -6.06 7 333 Best Double Couple:Mo=6.8*10**15 NP1:Strike= 21 Dip=60 Slip= 22 NP2: 280 71 149 |
(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 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 10 65 -25 3.66 0.1594 WVFGRD96 1.0 25 85 5 3.66 0.1720 WVFGRD96 2.0 25 75 15 3.79 0.2303 WVFGRD96 3.0 25 65 10 3.85 0.2540 WVFGRD96 4.0 20 65 -5 3.87 0.2769 WVFGRD96 5.0 20 65 -5 3.90 0.2979 WVFGRD96 6.0 20 65 -5 3.93 0.3151 WVFGRD96 7.0 20 70 -5 3.95 0.3302 WVFGRD96 8.0 20 65 -10 3.99 0.3432 WVFGRD96 9.0 20 65 -10 4.00 0.3530 WVFGRD96 10.0 20 65 -10 4.01 0.3604 WVFGRD96 11.0 20 70 -15 4.03 0.3670 WVFGRD96 12.0 20 70 -15 4.05 0.3725 WVFGRD96 13.0 20 70 -15 4.06 0.3767 WVFGRD96 14.0 20 70 -15 4.07 0.3799 WVFGRD96 15.0 20 70 -15 4.08 0.3831 WVFGRD96 16.0 15 70 -20 4.09 0.3868 WVFGRD96 17.0 15 70 -20 4.10 0.3900 WVFGRD96 18.0 15 70 -20 4.11 0.3932 WVFGRD96 19.0 15 70 -20 4.12 0.3966 WVFGRD96 20.0 15 70 -20 4.13 0.3998 WVFGRD96 21.0 15 70 -20 4.14 0.4024 WVFGRD96 22.0 15 70 -15 4.14 0.4048 WVFGRD96 23.0 15 70 -20 4.15 0.4070 WVFGRD96 24.0 15 70 -15 4.16 0.4098 WVFGRD96 25.0 15 70 -15 4.17 0.4121 WVFGRD96 26.0 15 70 -15 4.17 0.4141 WVFGRD96 27.0 15 70 -10 4.18 0.4158 WVFGRD96 28.0 15 70 -10 4.19 0.4173 WVFGRD96 29.0 15 70 -10 4.20 0.4190 WVFGRD96 30.0 15 70 -10 4.20 0.4204 WVFGRD96 31.0 15 70 -10 4.21 0.4214 WVFGRD96 32.0 15 70 -5 4.22 0.4219 WVFGRD96 33.0 15 70 -5 4.23 0.4221 WVFGRD96 34.0 15 70 -5 4.24 0.4220 WVFGRD96 35.0 15 70 0 4.25 0.4231 WVFGRD96 36.0 15 70 0 4.26 0.4247 WVFGRD96 37.0 15 70 0 4.27 0.4262 WVFGRD96 38.0 15 70 0 4.28 0.4275 WVFGRD96 39.0 15 70 0 4.29 0.4284 WVFGRD96 40.0 15 60 5 4.34 0.4300 WVFGRD96 41.0 15 60 5 4.35 0.4305 WVFGRD96 42.0 15 60 5 4.35 0.4309 WVFGRD96 43.0 15 65 5 4.36 0.4313 WVFGRD96 44.0 15 65 5 4.37 0.4319 WVFGRD96 45.0 15 65 10 4.38 0.4327 WVFGRD96 46.0 15 65 10 4.39 0.4334 WVFGRD96 47.0 20 65 15 4.40 0.4345 WVFGRD96 48.0 20 65 15 4.40 0.4362 WVFGRD96 49.0 20 65 20 4.42 0.4388 WVFGRD96 50.0 20 65 20 4.42 0.4422 WVFGRD96 51.0 20 65 20 4.43 0.4453 WVFGRD96 52.0 20 65 20 4.44 0.4483 WVFGRD96 53.0 20 65 20 4.44 0.4513 WVFGRD96 54.0 20 65 20 4.45 0.4545 WVFGRD96 55.0 20 65 20 4.46 0.4573 WVFGRD96 56.0 20 65 20 4.46 0.4598 WVFGRD96 57.0 20 65 20 4.47 0.4625 WVFGRD96 58.0 20 65 20 4.47 0.4655 WVFGRD96 59.0 20 65 20 4.48 0.4679 WVFGRD96 60.0 20 65 20 4.48 0.4694 WVFGRD96 61.0 20 65 20 4.49 0.4711 WVFGRD96 62.0 20 65 20 4.49 0.4735 WVFGRD96 63.0 20 65 20 4.50 0.4748 WVFGRD96 64.0 20 65 20 4.50 0.4760 WVFGRD96 65.0 20 65 20 4.50 0.4774 WVFGRD96 66.0 20 65 20 4.51 0.4783 WVFGRD96 67.0 20 65 20 4.51 0.4793 WVFGRD96 68.0 20 65 20 4.51 0.4794 WVFGRD96 69.0 20 65 20 4.52 0.4803 WVFGRD96 70.0 20 65 20 4.52 0.4808 WVFGRD96 71.0 20 65 20 4.52 0.4802 WVFGRD96 72.0 20 65 20 4.53 0.4810 WVFGRD96 73.0 20 65 20 4.53 0.4803 WVFGRD96 74.0 20 65 20 4.53 0.4801 WVFGRD96 75.0 20 65 20 4.54 0.4801 WVFGRD96 76.0 20 65 20 4.54 0.4785 WVFGRD96 77.0 20 65 20 4.54 0.4788 WVFGRD96 78.0 20 65 20 4.54 0.4776 WVFGRD96 79.0 20 65 20 4.55 0.4767 WVFGRD96 80.0 20 65 20 4.55 0.4756 WVFGRD96 81.0 20 65 20 4.55 0.4742 WVFGRD96 82.0 20 65 20 4.55 0.4734 WVFGRD96 83.0 20 65 20 4.56 0.4715 WVFGRD96 84.0 20 65 20 4.56 0.4707 WVFGRD96 85.0 20 65 20 4.56 0.4688 WVFGRD96 86.0 20 65 20 4.56 0.4674 WVFGRD96 87.0 20 65 20 4.56 0.4659 WVFGRD96 88.0 25 65 20 4.56 0.4642 WVFGRD96 89.0 25 65 20 4.57 0.4631 WVFGRD96 90.0 25 65 20 4.57 0.4615 WVFGRD96 91.0 25 65 20 4.57 0.4602 WVFGRD96 92.0 25 65 20 4.57 0.4586 WVFGRD96 93.0 25 65 20 4.57 0.4570 WVFGRD96 94.0 25 70 20 4.58 0.4555 WVFGRD96 95.0 25 70 20 4.58 0.4542 WVFGRD96 96.0 25 70 20 4.58 0.4530 WVFGRD96 97.0 25 70 20 4.58 0.4515 WVFGRD96 98.0 25 70 20 4.58 0.4503 WVFGRD96 99.0 25 70 20 4.59 0.4489
The best solution is
WVFGRD96 72.0 20 65 20 4.53 0.4810
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
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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: