2013/08/04 07:57:54 61.410 -149.886 18.3 3.9 Alaska
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution ENS 2013/08/04 07:57:54:0 61.41 -149.89 18.3 3.9 Alaska Stations used: AK.FID AK.GHO AK.GLI AK.RC01 AK.SAW AK.SCM AK.SKN AK.SSN AK.SWD AT.PMR Filtering commands used: cut a -30 a 120 rtr taper w 0.1 hp c 0.02 n 3 lp c 0.06 n 3 Best Fitting Double Couple Mo = 1.02e+22 dyne-cm Mw = 3.94 Z = 48 km Plane Strike Dip Rake NP1 220 70 -60 NP2 341 36 -144 Principal Axes: Axis Value Plunge Azimuth T 1.02e+22 19 288 N 0.00e+00 28 29 P -1.02e+22 55 168 Moment Tensor: (dyne-cm) Component Value Mxx -2.38e+21 Mxy -1.97e+21 Mxz 5.70e+21 Myy 8.08e+21 Myz -4.08e+21 Mzz -5.70e+21 ##------------ ############---------- ##################---------# ######################-####### ######################---######### #####################-------######## ####################----------######## ## ##############-------------######## ## T ############----------------####### ### ###########-----------------######## ###############--------------------####### ##############---------------------####### #############----------------------####### ###########-----------------------###### ##########---------- -----------###### ########----------- P -----------##### ######------------ ----------##### ####-------------------------##### ##-------------------------### #-----------------------#### --------------------## -------------- Global CMT Convention Moment Tensor: R T P -5.70e+21 5.70e+21 4.08e+21 5.70e+21 -2.38e+21 1.97e+21 4.08e+21 1.97e+21 8.08e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20130804075754/index.html |
STK = 220 DIP = 70 RAKE = -60 MW = 3.94 HS = 48.0
The NDK file is 20130804075754.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2013/08/04 07:57:54:0 61.41 -149.89 18.3 3.9 Alaska Stations used: AK.FID AK.GHO AK.GLI AK.RC01 AK.SAW AK.SCM AK.SKN AK.SSN AK.SWD AT.PMR Filtering commands used: cut a -30 a 120 rtr taper w 0.1 hp c 0.02 n 3 lp c 0.06 n 3 Best Fitting Double Couple Mo = 1.02e+22 dyne-cm Mw = 3.94 Z = 48 km Plane Strike Dip Rake NP1 220 70 -60 NP2 341 36 -144 Principal Axes: Axis Value Plunge Azimuth T 1.02e+22 19 288 N 0.00e+00 28 29 P -1.02e+22 55 168 Moment Tensor: (dyne-cm) Component Value Mxx -2.38e+21 Mxy -1.97e+21 Mxz 5.70e+21 Myy 8.08e+21 Myz -4.08e+21 Mzz -5.70e+21 ##------------ ############---------- ##################---------# ######################-####### ######################---######### #####################-------######## ####################----------######## ## ##############-------------######## ## T ############----------------####### ### ###########-----------------######## ###############--------------------####### ##############---------------------####### #############----------------------####### ###########-----------------------###### ##########---------- -----------###### ########----------- P -----------##### ######------------ ----------##### ####-------------------------##### ##-------------------------### #-----------------------#### --------------------## -------------- Global CMT Convention Moment Tensor: R T P -5.70e+21 5.70e+21 4.08e+21 5.70e+21 -2.38e+21 1.97e+21 4.08e+21 1.97e+21 8.08e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20130804075754/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:
cut a -30 a 120 rtr taper w 0.1 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 0.5 195 45 85 3.21 0.2647 WVFGRD96 1.0 195 45 90 3.24 0.2639 WVFGRD96 2.0 195 45 85 3.37 0.3454 WVFGRD96 3.0 190 50 80 3.42 0.3495 WVFGRD96 4.0 15 45 -90 3.46 0.3489 WVFGRD96 5.0 225 80 -10 3.42 0.3568 WVFGRD96 6.0 230 80 -5 3.43 0.3697 WVFGRD96 7.0 240 70 -5 3.45 0.3840 WVFGRD96 8.0 240 70 -5 3.48 0.3994 WVFGRD96 9.0 70 60 30 3.52 0.4079 WVFGRD96 10.0 70 65 30 3.54 0.4210 WVFGRD96 11.0 70 65 30 3.55 0.4353 WVFGRD96 12.0 70 65 30 3.56 0.4481 WVFGRD96 13.0 70 65 30 3.57 0.4591 WVFGRD96 14.0 70 65 30 3.59 0.4688 WVFGRD96 15.0 75 65 25 3.60 0.4779 WVFGRD96 16.0 70 70 30 3.61 0.4863 WVFGRD96 17.0 70 70 25 3.62 0.4941 WVFGRD96 18.0 70 70 25 3.63 0.5016 WVFGRD96 19.0 70 70 25 3.64 0.5087 WVFGRD96 20.0 70 70 25 3.65 0.5148 WVFGRD96 21.0 230 70 -35 3.67 0.5247 WVFGRD96 22.0 230 70 -40 3.68 0.5380 WVFGRD96 23.0 230 70 -40 3.69 0.5510 WVFGRD96 24.0 230 70 -40 3.69 0.5625 WVFGRD96 25.0 230 70 -40 3.70 0.5734 WVFGRD96 26.0 230 70 -40 3.71 0.5840 WVFGRD96 27.0 230 70 -40 3.72 0.5926 WVFGRD96 28.0 230 70 -40 3.72 0.6010 WVFGRD96 29.0 230 70 -40 3.73 0.6076 WVFGRD96 30.0 230 75 -45 3.74 0.6138 WVFGRD96 31.0 230 75 -45 3.75 0.6220 WVFGRD96 32.0 230 75 -45 3.75 0.6281 WVFGRD96 33.0 225 70 -45 3.76 0.6349 WVFGRD96 34.0 225 70 -45 3.76 0.6399 WVFGRD96 35.0 225 70 -45 3.77 0.6464 WVFGRD96 36.0 225 70 -45 3.78 0.6518 WVFGRD96 37.0 225 70 -45 3.79 0.6570 WVFGRD96 38.0 225 70 -45 3.79 0.6607 WVFGRD96 39.0 220 70 -45 3.81 0.6653 WVFGRD96 40.0 225 70 -60 3.90 0.6621 WVFGRD96 41.0 225 70 -55 3.90 0.6679 WVFGRD96 42.0 225 70 -55 3.91 0.6722 WVFGRD96 43.0 220 70 -55 3.91 0.6767 WVFGRD96 44.0 220 70 -55 3.92 0.6794 WVFGRD96 45.0 220 70 -55 3.93 0.6820 WVFGRD96 46.0 220 70 -55 3.93 0.6831 WVFGRD96 47.0 220 70 -60 3.94 0.6837 WVFGRD96 48.0 220 70 -60 3.94 0.6839 WVFGRD96 49.0 220 70 -60 3.95 0.6832 WVFGRD96 50.0 220 70 -60 3.95 0.6822 WVFGRD96 51.0 220 70 -60 3.95 0.6801 WVFGRD96 52.0 220 70 -60 3.96 0.6781 WVFGRD96 53.0 220 70 -60 3.96 0.6752 WVFGRD96 54.0 220 70 -60 3.96 0.6725 WVFGRD96 55.0 220 70 -60 3.96 0.6692 WVFGRD96 56.0 220 70 -60 3.97 0.6650 WVFGRD96 57.0 220 70 -60 3.97 0.6615 WVFGRD96 58.0 220 70 -60 3.97 0.6562 WVFGRD96 59.0 215 70 -60 3.97 0.6533 WVFGRD96 60.0 215 70 -60 3.98 0.6490 WVFGRD96 61.0 215 70 -60 3.98 0.6451 WVFGRD96 62.0 215 70 -60 3.98 0.6406 WVFGRD96 63.0 215 70 -60 3.98 0.6363 WVFGRD96 64.0 215 70 -60 3.98 0.6328 WVFGRD96 65.0 215 70 -60 3.98 0.6281 WVFGRD96 66.0 215 70 -60 3.98 0.6238 WVFGRD96 67.0 215 70 -60 3.99 0.6204 WVFGRD96 68.0 215 70 -60 3.99 0.6152 WVFGRD96 69.0 215 70 -60 3.99 0.6114 WVFGRD96 70.0 215 70 -60 3.99 0.6073 WVFGRD96 71.0 215 70 -60 3.99 0.6021 WVFGRD96 72.0 215 70 -60 3.99 0.5988 WVFGRD96 73.0 215 70 -60 3.99 0.5943 WVFGRD96 74.0 215 70 -60 3.99 0.5894 WVFGRD96 75.0 215 70 -60 3.99 0.5860 WVFGRD96 76.0 215 75 -60 4.00 0.5817 WVFGRD96 77.0 215 75 -60 4.00 0.5786 WVFGRD96 78.0 215 75 -60 4.00 0.5754 WVFGRD96 79.0 215 75 -60 4.00 0.5729 WVFGRD96 80.0 215 75 -65 4.00 0.5696 WVFGRD96 81.0 215 75 -65 4.01 0.5664 WVFGRD96 82.0 215 75 -65 4.01 0.5643 WVFGRD96 83.0 215 75 -65 4.01 0.5611 WVFGRD96 84.0 215 75 -65 4.01 0.5579 WVFGRD96 85.0 215 75 -65 4.01 0.5554 WVFGRD96 86.0 215 75 -65 4.01 0.5531 WVFGRD96 87.0 215 75 -70 4.01 0.5494 WVFGRD96 88.0 215 80 -70 4.02 0.5475 WVFGRD96 89.0 215 80 -70 4.02 0.5457 WVFGRD96 90.0 215 80 -70 4.03 0.5442 WVFGRD96 91.0 215 80 -75 4.03 0.5414 WVFGRD96 92.0 215 80 -75 4.03 0.5408 WVFGRD96 93.0 215 80 -80 4.04 0.5388 WVFGRD96 94.0 215 80 -85 4.05 0.5373 WVFGRD96 95.0 215 80 -85 4.05 0.5356 WVFGRD96 96.0 215 80 -85 4.05 0.5345 WVFGRD96 97.0 215 80 -85 4.05 0.5329 WVFGRD96 98.0 215 80 -85 4.05 0.5307 WVFGRD96 99.0 215 80 -85 4.05 0.5291 WVFGRD96 100.0 215 80 -85 4.05 0.5273 WVFGRD96 101.0 215 80 -85 4.06 0.5255 WVFGRD96 102.0 15 10 -110 4.06 0.5228 WVFGRD96 103.0 215 80 -85 4.06 0.5211 WVFGRD96 104.0 215 80 -90 4.07 0.5189 WVFGRD96 105.0 215 80 -90 4.07 0.5168 WVFGRD96 106.0 215 80 -90 4.07 0.5144 WVFGRD96 107.0 215 80 -90 4.07 0.5117 WVFGRD96 108.0 10 10 -110 4.07 0.5103 WVFGRD96 109.0 10 10 -110 4.07 0.5075 WVFGRD96 110.0 50 10 -75 4.08 0.5049 WVFGRD96 111.0 50 10 -70 4.08 0.5024 WVFGRD96 112.0 60 10 -60 4.09 0.5002 WVFGRD96 113.0 60 10 -60 4.09 0.4982 WVFGRD96 114.0 60 10 -60 4.09 0.4954 WVFGRD96 115.0 65 10 -55 4.10 0.4926 WVFGRD96 116.0 65 10 -55 4.10 0.4907 WVFGRD96 117.0 65 10 -55 4.10 0.4879 WVFGRD96 118.0 65 10 -55 4.10 0.4858 WVFGRD96 119.0 70 10 -50 4.10 0.4828 WVFGRD96 120.0 70 10 -50 4.10 0.4799 WVFGRD96 121.0 70 10 -50 4.10 0.4780 WVFGRD96 122.0 50 5 -70 4.10 0.4753 WVFGRD96 123.0 50 5 -70 4.10 0.4726 WVFGRD96 124.0 50 5 -70 4.10 0.4697 WVFGRD96 125.0 60 5 -60 4.10 0.4668 WVFGRD96 126.0 60 5 -60 4.10 0.4647 WVFGRD96 127.0 60 5 -60 4.10 0.4622 WVFGRD96 128.0 60 5 -60 4.11 0.4590 WVFGRD96 129.0 60 5 -60 4.11 0.4565
The best solution is
WVFGRD96 48.0 220 70 -60 3.94 0.6839
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 a -30 a 120 rtr taper w 0.1 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: