2013/03/10 21:05:18 61.510 -150.478 4.2 61.2 Alaska
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution ENS 2013/03/10 21:05:18:0 61.51 -150.48 4.2 61.2 Alaska Stations used: AK.CAST AK.DIV AK.HIN AK.KNK AK.PPLA AK.RC01 AK.RIDG AK.SAW AK.SCM AK.SSN AK.SWD AT.MENT AT.PMR Filtering commands used: hp c 0.02 n 3 lp c 0.06 n 3 Best Fitting Double Couple Mo = 2.69e+22 dyne-cm Mw = 4.22 Z = 71 km Plane Strike Dip Rake NP1 145 90 -155 NP2 55 65 0 Principal Axes: Axis Value Plunge Azimuth T 2.69e+22 17 277 N 0.00e+00 65 145 P -2.69e+22 17 13 Moment Tensor: (dyne-cm) Component Value Mxx -2.29e+22 Mxy -8.34e+21 Mxz -6.52e+21 Myy 2.29e+22 Myz -9.32e+21 Mzz 0.00e+00 --------- -- ------------- P ------ ###------------- --------- #####------------------------- #########------------------------- ###########------------------------# #############----------------------### ###############--------------------##### # #############-----------------###### ## T ##############--------------######### ## ###############------------########## ######################--------############ #######################-----############## #######################-################ ######################---############### ##################-------############# ############-------------########### -##----------------------######### -------------------------##### -------------------------### ---------------------- -------------- Global CMT Convention Moment Tensor: R T P 0.00e+00 -6.52e+21 9.32e+21 -6.52e+21 -2.29e+22 8.34e+21 9.32e+21 8.34e+21 2.29e+22 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20130310210518/index.html |
STK = 55 DIP = 65 RAKE = 0 MW = 4.22 HS = 71.0
The NDK file is 20130310210518.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2013/03/10 21:05:18:0 61.51 -150.48 4.2 61.2 Alaska Stations used: AK.CAST AK.DIV AK.HIN AK.KNK AK.PPLA AK.RC01 AK.RIDG AK.SAW AK.SCM AK.SSN AK.SWD AT.MENT AT.PMR Filtering commands used: hp c 0.02 n 3 lp c 0.06 n 3 Best Fitting Double Couple Mo = 2.69e+22 dyne-cm Mw = 4.22 Z = 71 km Plane Strike Dip Rake NP1 145 90 -155 NP2 55 65 0 Principal Axes: Axis Value Plunge Azimuth T 2.69e+22 17 277 N 0.00e+00 65 145 P -2.69e+22 17 13 Moment Tensor: (dyne-cm) Component Value Mxx -2.29e+22 Mxy -8.34e+21 Mxz -6.52e+21 Myy 2.29e+22 Myz -9.32e+21 Mzz 0.00e+00 --------- -- ------------- P ------ ###------------- --------- #####------------------------- #########------------------------- ###########------------------------# #############----------------------### ###############--------------------##### # #############-----------------###### ## T ##############--------------######### ## ###############------------########## ######################--------############ #######################-----############## #######################-################ ######################---############### ##################-------############# ############-------------########### -##----------------------######### -------------------------##### -------------------------### ---------------------- -------------- Global CMT Convention Moment Tensor: R T P 0.00e+00 -6.52e+21 9.32e+21 -6.52e+21 -2.29e+22 8.34e+21 9.32e+21 8.34e+21 2.29e+22 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20130310210518/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 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 50 55 -15 3.24 0.1165 WVFGRD96 1.0 50 60 -10 3.28 0.1303 WVFGRD96 2.0 55 55 0 3.42 0.1849 WVFGRD96 3.0 55 55 5 3.49 0.2140 WVFGRD96 4.0 55 60 20 3.55 0.2415 WVFGRD96 5.0 55 65 20 3.57 0.2678 WVFGRD96 6.0 55 65 20 3.60 0.2877 WVFGRD96 7.0 50 70 15 3.63 0.3107 WVFGRD96 8.0 50 65 15 3.68 0.3340 WVFGRD96 9.0 50 65 15 3.70 0.3533 WVFGRD96 10.0 50 70 15 3.72 0.3702 WVFGRD96 11.0 50 70 15 3.73 0.3818 WVFGRD96 12.0 50 70 10 3.74 0.3943 WVFGRD96 13.0 50 70 10 3.76 0.4044 WVFGRD96 14.0 50 75 10 3.77 0.4130 WVFGRD96 15.0 50 75 10 3.78 0.4226 WVFGRD96 16.0 50 75 10 3.79 0.4308 WVFGRD96 17.0 50 75 5 3.80 0.4364 WVFGRD96 18.0 50 80 10 3.81 0.4439 WVFGRD96 19.0 50 80 10 3.82 0.4495 WVFGRD96 20.0 50 80 5 3.83 0.4568 WVFGRD96 21.0 55 80 10 3.83 0.4620 WVFGRD96 22.0 55 80 10 3.84 0.4684 WVFGRD96 23.0 55 80 10 3.85 0.4731 WVFGRD96 24.0 55 80 10 3.86 0.4790 WVFGRD96 25.0 55 80 5 3.87 0.4842 WVFGRD96 26.0 55 80 5 3.88 0.4902 WVFGRD96 27.0 55 80 5 3.89 0.4951 WVFGRD96 28.0 55 80 5 3.90 0.5005 WVFGRD96 29.0 55 80 5 3.90 0.5063 WVFGRD96 30.0 55 80 5 3.91 0.5119 WVFGRD96 31.0 50 85 5 3.93 0.5179 WVFGRD96 32.0 50 85 5 3.94 0.5232 WVFGRD96 33.0 50 85 5 3.96 0.5289 WVFGRD96 34.0 50 85 5 3.97 0.5346 WVFGRD96 35.0 50 85 5 3.98 0.5392 WVFGRD96 36.0 50 85 0 3.99 0.5431 WVFGRD96 37.0 50 85 0 4.01 0.5487 WVFGRD96 38.0 50 85 0 4.02 0.5544 WVFGRD96 39.0 50 85 0 4.04 0.5597 WVFGRD96 40.0 50 80 0 4.06 0.5662 WVFGRD96 41.0 50 80 0 4.07 0.5696 WVFGRD96 42.0 50 80 0 4.08 0.5717 WVFGRD96 43.0 50 80 0 4.09 0.5733 WVFGRD96 44.0 50 80 0 4.10 0.5763 WVFGRD96 45.0 50 80 0 4.10 0.5785 WVFGRD96 46.0 50 80 0 4.11 0.5796 WVFGRD96 47.0 50 80 0 4.12 0.5824 WVFGRD96 48.0 50 80 0 4.13 0.5843 WVFGRD96 49.0 50 80 0 4.13 0.5850 WVFGRD96 50.0 50 80 0 4.14 0.5875 WVFGRD96 51.0 50 80 0 4.15 0.5886 WVFGRD96 52.0 50 80 0 4.15 0.5894 WVFGRD96 53.0 50 80 0 4.16 0.5911 WVFGRD96 54.0 50 80 0 4.16 0.5912 WVFGRD96 55.0 50 80 0 4.17 0.5927 WVFGRD96 56.0 50 75 0 4.17 0.5931 WVFGRD96 57.0 50 75 0 4.17 0.5941 WVFGRD96 58.0 50 75 0 4.18 0.5948 WVFGRD96 59.0 50 75 5 4.18 0.5957 WVFGRD96 60.0 50 75 5 4.19 0.5969 WVFGRD96 61.0 50 75 5 4.19 0.5975 WVFGRD96 62.0 50 75 5 4.20 0.5985 WVFGRD96 63.0 50 75 5 4.20 0.5986 WVFGRD96 64.0 50 75 5 4.21 0.5993 WVFGRD96 65.0 50 75 5 4.21 0.5989 WVFGRD96 66.0 55 65 0 4.20 0.5996 WVFGRD96 67.0 55 65 0 4.20 0.6000 WVFGRD96 68.0 55 65 0 4.21 0.6002 WVFGRD96 69.0 55 65 0 4.21 0.6003 WVFGRD96 70.0 55 65 0 4.21 0.5999 WVFGRD96 71.0 55 65 0 4.22 0.6004 WVFGRD96 72.0 55 65 0 4.22 0.5988 WVFGRD96 73.0 55 65 0 4.22 0.5991 WVFGRD96 74.0 55 65 0 4.23 0.5981 WVFGRD96 75.0 55 65 5 4.23 0.5974 WVFGRD96 76.0 55 65 5 4.23 0.5965 WVFGRD96 77.0 55 65 5 4.24 0.5953 WVFGRD96 78.0 55 65 5 4.24 0.5953 WVFGRD96 79.0 55 65 5 4.24 0.5935 WVFGRD96 80.0 55 65 5 4.25 0.5927 WVFGRD96 81.0 55 65 5 4.25 0.5915 WVFGRD96 82.0 55 65 5 4.25 0.5888 WVFGRD96 83.0 55 65 5 4.25 0.5885 WVFGRD96 84.0 55 65 10 4.26 0.5865 WVFGRD96 85.0 55 65 10 4.26 0.5845 WVFGRD96 86.0 55 65 10 4.26 0.5838 WVFGRD96 87.0 55 65 10 4.26 0.5815 WVFGRD96 88.0 55 65 10 4.27 0.5797 WVFGRD96 89.0 55 65 10 4.27 0.5783 WVFGRD96 90.0 55 65 10 4.27 0.5757 WVFGRD96 91.0 55 65 10 4.27 0.5739 WVFGRD96 92.0 55 65 10 4.28 0.5720 WVFGRD96 93.0 55 65 10 4.28 0.5692 WVFGRD96 94.0 55 65 15 4.28 0.5669 WVFGRD96 95.0 55 65 15 4.28 0.5654 WVFGRD96 96.0 55 65 15 4.28 0.5627 WVFGRD96 97.0 55 65 15 4.29 0.5606 WVFGRD96 98.0 55 65 15 4.29 0.5587 WVFGRD96 99.0 55 65 15 4.29 0.5563
The best solution is
WVFGRD96 71.0 55 65 0 4.22 0.6004
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: