2011/07/02 11:45:06 63.118 -150.858 122 4.40 Alaska
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution ENS 2011/07/02 11:45:06:0 63.12 -150.86 122.0 4.4 Alaska Stations used: AK.BPAW AK.BRLK AK.CAST AK.CCB AK.DHY AK.FIB AK.KLU AK.KTH AK.MCK AK.MLY AK.PPLA AK.RC01 AK.SAW AK.SSN AK.SWD AK.TRF AK.WRH AT.PMR IU.COLA Filtering commands used: hp c 0.02 n 3 lp c 0.06 n 3 Best Fitting Double Couple Mo = 3.67e+22 dyne-cm Mw = 4.31 Z = 133 km Plane Strike Dip Rake NP1 55 75 85 NP2 254 16 108 Principal Axes: Axis Value Plunge Azimuth T 3.67e+22 60 318 N 0.00e+00 5 56 P -3.67e+22 30 149 Moment Tensor: (dyne-cm) Component Value Mxx -1.52e+22 Mxy 7.54e+21 Mxz 2.55e+22 Myy -3.11e+21 Myz -1.89e+22 Mzz 1.83e+22 -------------- ---------#######------ ------##################---- ----########################-- ---##############################- ---###############################-# --########## ###################---- --########### T #################------- -############ ###############--------- --#############################----------- -###########################-------------- -#########################---------------- -#######################------------------ ####################-------------------- #################----------------------- #############------------------------- #######----------------- --------- ----------------------- P -------- --------------------- ------ ---------------------------- ---------------------- -------------- Global CMT Convention Moment Tensor: R T P 1.83e+22 2.55e+22 1.89e+22 2.55e+22 -1.52e+22 -7.54e+21 1.89e+22 -7.54e+21 -3.11e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20110702114506/index.html |
STK = 55 DIP = 75 RAKE = 85 MW = 4.31 HS = 133.0
The NDK file is 20110702114506.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2011/07/02 11:45:06:0 63.12 -150.86 122.0 4.4 Alaska Stations used: AK.BPAW AK.BRLK AK.CAST AK.CCB AK.DHY AK.FIB AK.KLU AK.KTH AK.MCK AK.MLY AK.PPLA AK.RC01 AK.SAW AK.SSN AK.SWD AK.TRF AK.WRH AT.PMR IU.COLA Filtering commands used: hp c 0.02 n 3 lp c 0.06 n 3 Best Fitting Double Couple Mo = 3.67e+22 dyne-cm Mw = 4.31 Z = 133 km Plane Strike Dip Rake NP1 55 75 85 NP2 254 16 108 Principal Axes: Axis Value Plunge Azimuth T 3.67e+22 60 318 N 0.00e+00 5 56 P -3.67e+22 30 149 Moment Tensor: (dyne-cm) Component Value Mxx -1.52e+22 Mxy 7.54e+21 Mxz 2.55e+22 Myy -3.11e+21 Myz -1.89e+22 Mzz 1.83e+22 -------------- ---------#######------ ------##################---- ----########################-- ---##############################- ---###############################-# --########## ###################---- --########### T #################------- -############ ###############--------- --#############################----------- -###########################-------------- -#########################---------------- -#######################------------------ ####################-------------------- #################----------------------- #############------------------------- #######----------------- --------- ----------------------- P -------- --------------------- ------ ---------------------------- ---------------------- -------------- Global CMT Convention Moment Tensor: R T P 1.83e+22 2.55e+22 1.89e+22 2.55e+22 -1.52e+22 -7.54e+21 1.89e+22 -7.54e+21 -3.11e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20110702114506/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 0.5 110 40 -70 3.38 0.2148 WVFGRD96 1.0 105 40 -80 3.42 0.2168 WVFGRD96 2.0 115 45 -65 3.52 0.2799 WVFGRD96 3.0 135 50 -40 3.56 0.2893 WVFGRD96 4.0 145 65 -15 3.54 0.2929 WVFGRD96 5.0 335 65 20 3.57 0.3043 WVFGRD96 6.0 335 65 20 3.60 0.3204 WVFGRD96 7.0 335 65 15 3.61 0.3314 WVFGRD96 8.0 340 60 20 3.66 0.3456 WVFGRD96 9.0 340 60 20 3.68 0.3556 WVFGRD96 10.0 340 60 20 3.69 0.3645 WVFGRD96 11.0 340 55 15 3.70 0.3675 WVFGRD96 12.0 340 55 15 3.71 0.3753 WVFGRD96 13.0 340 55 20 3.72 0.3787 WVFGRD96 14.0 340 55 20 3.73 0.3835 WVFGRD96 15.0 340 55 20 3.73 0.3883 WVFGRD96 16.0 340 60 20 3.74 0.3875 WVFGRD96 17.0 340 60 20 3.75 0.3895 WVFGRD96 18.0 340 60 20 3.75 0.3876 WVFGRD96 19.0 345 60 20 3.77 0.3863 WVFGRD96 20.0 345 60 20 3.78 0.3871 WVFGRD96 21.0 230 80 -35 3.76 0.3874 WVFGRD96 22.0 230 80 -35 3.77 0.3898 WVFGRD96 23.0 230 80 -35 3.78 0.3921 WVFGRD96 24.0 230 80 -35 3.78 0.3842 WVFGRD96 25.0 215 85 -35 3.79 0.3875 WVFGRD96 26.0 35 85 30 3.82 0.3911 WVFGRD96 27.0 35 85 30 3.83 0.3945 WVFGRD96 28.0 35 85 30 3.83 0.3880 WVFGRD96 29.0 35 85 30 3.84 0.3931 WVFGRD96 30.0 35 90 30 3.84 0.3969 WVFGRD96 31.0 35 90 30 3.85 0.4020 WVFGRD96 32.0 35 90 30 3.86 0.3955 WVFGRD96 33.0 40 85 30 3.87 0.4005 WVFGRD96 34.0 40 85 30 3.88 0.4051 WVFGRD96 35.0 40 85 30 3.89 0.3992 WVFGRD96 36.0 205 25 60 3.91 0.4069 WVFGRD96 37.0 205 25 60 3.92 0.4164 WVFGRD96 38.0 225 20 85 3.92 0.4161 WVFGRD96 39.0 50 70 90 3.93 0.4265 WVFGRD96 40.0 230 20 90 4.07 0.4410 WVFGRD96 41.0 230 20 90 4.08 0.4366 WVFGRD96 42.0 230 20 90 4.09 0.4387 WVFGRD96 43.0 55 70 95 4.09 0.4401 WVFGRD96 44.0 225 20 85 4.10 0.4394 WVFGRD96 45.0 225 20 85 4.11 0.4389 WVFGRD96 46.0 55 70 95 4.11 0.4349 WVFGRD96 47.0 220 20 80 4.12 0.4324 WVFGRD96 48.0 220 20 80 4.12 0.4294 WVFGRD96 49.0 195 70 -15 4.08 0.4357 WVFGRD96 50.0 195 70 -20 4.08 0.4351 WVFGRD96 51.0 195 70 -20 4.09 0.4407 WVFGRD96 52.0 195 70 -20 4.10 0.4452 WVFGRD96 53.0 195 70 -20 4.10 0.4491 WVFGRD96 54.0 195 70 -20 4.11 0.4521 WVFGRD96 55.0 195 70 -20 4.12 0.4559 WVFGRD96 56.0 195 70 -20 4.12 0.4591 WVFGRD96 57.0 195 70 -20 4.13 0.4626 WVFGRD96 58.0 195 70 -20 4.14 0.4663 WVFGRD96 59.0 195 70 -20 4.14 0.4686 WVFGRD96 60.0 195 70 -20 4.15 0.4719 WVFGRD96 61.0 195 70 -20 4.15 0.4736 WVFGRD96 62.0 55 65 80 4.18 0.4741 WVFGRD96 63.0 55 65 80 4.19 0.4850 WVFGRD96 64.0 55 65 80 4.19 0.4956 WVFGRD96 65.0 55 65 80 4.20 0.5065 WVFGRD96 66.0 60 65 85 4.20 0.5164 WVFGRD96 67.0 60 65 85 4.21 0.5261 WVFGRD96 68.0 60 65 85 4.21 0.5358 WVFGRD96 69.0 55 65 80 4.21 0.5442 WVFGRD96 70.0 55 70 80 4.21 0.5536 WVFGRD96 71.0 55 70 80 4.22 0.5639 WVFGRD96 72.0 55 70 80 4.22 0.5733 WVFGRD96 73.0 55 70 80 4.22 0.5841 WVFGRD96 74.0 55 70 80 4.22 0.5929 WVFGRD96 75.0 55 70 80 4.23 0.6011 WVFGRD96 76.0 55 70 80 4.23 0.6109 WVFGRD96 77.0 55 70 80 4.23 0.6195 WVFGRD96 78.0 55 70 80 4.23 0.6260 WVFGRD96 79.0 55 70 80 4.24 0.6345 WVFGRD96 80.0 55 70 80 4.24 0.6429 WVFGRD96 81.0 55 70 80 4.24 0.6496 WVFGRD96 82.0 55 70 80 4.24 0.6573 WVFGRD96 83.0 55 70 80 4.25 0.6649 WVFGRD96 84.0 55 70 80 4.25 0.6720 WVFGRD96 85.0 55 70 80 4.25 0.6780 WVFGRD96 86.0 55 70 80 4.25 0.6843 WVFGRD96 87.0 55 70 80 4.25 0.6912 WVFGRD96 88.0 55 70 80 4.25 0.6960 WVFGRD96 89.0 55 70 80 4.26 0.7022 WVFGRD96 90.0 55 70 80 4.26 0.7077 WVFGRD96 91.0 55 70 80 4.26 0.7124 WVFGRD96 92.0 55 70 80 4.26 0.7174 WVFGRD96 93.0 55 70 80 4.26 0.7220 WVFGRD96 94.0 55 70 80 4.26 0.7271 WVFGRD96 95.0 55 70 80 4.27 0.7311 WVFGRD96 96.0 55 70 80 4.27 0.7349 WVFGRD96 97.0 55 70 80 4.27 0.7395 WVFGRD96 98.0 55 70 80 4.27 0.7430 WVFGRD96 99.0 55 70 80 4.27 0.7459 WVFGRD96 100.0 55 70 80 4.27 0.7500 WVFGRD96 101.0 55 70 80 4.27 0.7528 WVFGRD96 102.0 55 70 80 4.27 0.7555 WVFGRD96 103.0 55 70 80 4.28 0.7585 WVFGRD96 104.0 55 70 80 4.28 0.7609 WVFGRD96 105.0 55 70 80 4.28 0.7635 WVFGRD96 106.0 55 70 80 4.28 0.7655 WVFGRD96 107.0 55 70 80 4.28 0.7678 WVFGRD96 108.0 55 70 80 4.28 0.7696 WVFGRD96 109.0 55 70 80 4.28 0.7720 WVFGRD96 110.0 55 70 80 4.28 0.7731 WVFGRD96 111.0 55 70 80 4.29 0.7747 WVFGRD96 112.0 55 70 80 4.29 0.7765 WVFGRD96 113.0 55 70 80 4.29 0.7776 WVFGRD96 114.0 55 70 80 4.29 0.7785 WVFGRD96 115.0 55 70 80 4.29 0.7800 WVFGRD96 116.0 55 70 80 4.29 0.7809 WVFGRD96 117.0 55 70 80 4.29 0.7816 WVFGRD96 118.0 55 70 80 4.29 0.7828 WVFGRD96 119.0 55 70 80 4.29 0.7833 WVFGRD96 120.0 55 70 80 4.30 0.7841 WVFGRD96 121.0 55 70 80 4.30 0.7846 WVFGRD96 122.0 55 70 80 4.30 0.7851 WVFGRD96 123.0 55 75 80 4.30 0.7857 WVFGRD96 124.0 55 75 80 4.30 0.7856 WVFGRD96 125.0 55 75 80 4.30 0.7864 WVFGRD96 126.0 55 75 80 4.30 0.7863 WVFGRD96 127.0 55 75 80 4.30 0.7872 WVFGRD96 128.0 55 75 80 4.30 0.7872 WVFGRD96 129.0 55 75 85 4.30 0.7878 WVFGRD96 130.0 55 75 85 4.31 0.7875 WVFGRD96 131.0 55 75 85 4.31 0.7871 WVFGRD96 132.0 55 75 85 4.31 0.7881 WVFGRD96 133.0 55 75 85 4.31 0.7881 WVFGRD96 134.0 260 20 110 4.31 0.7880 WVFGRD96 135.0 55 75 85 4.31 0.7873 WVFGRD96 136.0 55 75 85 4.31 0.7870 WVFGRD96 137.0 260 20 110 4.31 0.7874 WVFGRD96 138.0 260 20 110 4.31 0.7867 WVFGRD96 139.0 55 75 85 4.31 0.7861
The best solution is
WVFGRD96 133.0 55 75 85 4.31 0.7881
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 0.06 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: