2011/07/21 06:20:11 60.042 -152.853 94 4.10 Alaska
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution ENS 2011/07/21 06:20:11:0 60.04 -152.85 94.0 4.1 Alaska Stations used: AK.CNP AK.GHO AK.HOM AK.SAW AK.SSN AK.SWD AT.PMR AT.SVW2 II.KDAK Filtering commands used: hp c 0.02 n 3 lp c 0.10 n 3 Best Fitting Double Couple Mo = 3.43e+22 dyne-cm Mw = 4.29 Z = 112 km Plane Strike Dip Rake NP1 55 70 50 NP2 303 44 150 Principal Axes: Axis Value Plunge Azimuth T 3.43e+22 49 282 N 0.00e+00 37 71 P -3.43e+22 15 173 Moment Tensor: (dyne-cm) Component Value Mxx -3.08e+22 Mxy 8.49e+20 Mxz 1.22e+22 Myy 1.39e+22 Myz -1.77e+22 Mzz 1.69e+22 -------------- ---------------------- ---------------------------- ------##---------------------- -##################--------------- #######################-----------## ###########################-------#### ##############################----###### ######## #####################-####### ######### T ####################--######## ######### ##################------###### ############################---------##### ##########################-----------##### ######################---------------### ###################------------------### ###############----------------------# ##########-------------------------- ---------------------------------- ------------------------------ --------------- ---------- ------------ P ------- -------- --- Global CMT Convention Moment Tensor: R T P 1.69e+22 1.22e+22 1.77e+22 1.22e+22 -3.08e+22 -8.49e+20 1.77e+22 -8.49e+20 1.39e+22 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20110721062011/index.html |
STK = 55 DIP = 70 RAKE = 50 MW = 4.29 HS = 112.0
The NDK file is 20110721062011.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2011/07/21 06:20:11:0 60.04 -152.85 94.0 4.1 Alaska Stations used: AK.CNP AK.GHO AK.HOM AK.SAW AK.SSN AK.SWD AT.PMR AT.SVW2 II.KDAK Filtering commands used: hp c 0.02 n 3 lp c 0.10 n 3 Best Fitting Double Couple Mo = 3.43e+22 dyne-cm Mw = 4.29 Z = 112 km Plane Strike Dip Rake NP1 55 70 50 NP2 303 44 150 Principal Axes: Axis Value Plunge Azimuth T 3.43e+22 49 282 N 0.00e+00 37 71 P -3.43e+22 15 173 Moment Tensor: (dyne-cm) Component Value Mxx -3.08e+22 Mxy 8.49e+20 Mxz 1.22e+22 Myy 1.39e+22 Myz -1.77e+22 Mzz 1.69e+22 -------------- ---------------------- ---------------------------- ------##---------------------- -##################--------------- #######################-----------## ###########################-------#### ##############################----###### ######## #####################-####### ######### T ####################--######## ######### ##################------###### ############################---------##### ##########################-----------##### ######################---------------### ###################------------------### ###############----------------------# ##########-------------------------- ---------------------------------- ------------------------------ --------------- ---------- ------------ P ------- -------- --- Global CMT Convention Moment Tensor: R T P 1.69e+22 1.22e+22 1.77e+22 1.22e+22 -3.08e+22 -8.49e+20 1.77e+22 -8.49e+20 1.39e+22 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20110721062011/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 0.10 n 3The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT WVFGRD96 50.0 55 65 5 4.10 0.3193 WVFGRD96 51.0 55 60 5 4.11 0.3226 WVFGRD96 52.0 55 60 5 4.12 0.3258 WVFGRD96 53.0 60 70 10 4.14 0.3296 WVFGRD96 54.0 225 75 -30 4.12 0.3368 WVFGRD96 55.0 225 75 -30 4.13 0.3435 WVFGRD96 56.0 225 75 -30 4.14 0.3496 WVFGRD96 57.0 230 80 -30 4.16 0.3550 WVFGRD96 58.0 230 80 -30 4.16 0.3600 WVFGRD96 59.0 230 80 -30 4.17 0.3641 WVFGRD96 60.0 230 80 -30 4.18 0.3701 WVFGRD96 61.0 230 80 -30 4.18 0.3747 WVFGRD96 62.0 230 80 -30 4.19 0.3776 WVFGRD96 63.0 230 80 -30 4.19 0.3798 WVFGRD96 64.0 230 85 -30 4.19 0.3837 WVFGRD96 65.0 230 85 -30 4.19 0.3881 WVFGRD96 66.0 230 85 -30 4.20 0.3909 WVFGRD96 67.0 60 80 25 4.21 0.3925 WVFGRD96 68.0 60 80 25 4.21 0.3992 WVFGRD96 69.0 60 80 25 4.22 0.4043 WVFGRD96 70.0 60 75 35 4.20 0.4109 WVFGRD96 71.0 60 75 35 4.20 0.4196 WVFGRD96 72.0 60 70 35 4.19 0.4273 WVFGRD96 73.0 60 70 35 4.19 0.4331 WVFGRD96 74.0 60 70 35 4.20 0.4423 WVFGRD96 75.0 60 70 35 4.20 0.4492 WVFGRD96 76.0 60 70 35 4.21 0.4544 WVFGRD96 77.0 60 70 35 4.21 0.4630 WVFGRD96 78.0 60 70 40 4.21 0.4686 WVFGRD96 79.0 60 70 40 4.21 0.4755 WVFGRD96 80.0 60 70 40 4.22 0.4826 WVFGRD96 81.0 60 70 40 4.22 0.4873 WVFGRD96 82.0 60 70 40 4.23 0.4948 WVFGRD96 83.0 60 70 40 4.23 0.4996 WVFGRD96 84.0 60 70 40 4.23 0.5056 WVFGRD96 85.0 60 70 40 4.24 0.5114 WVFGRD96 86.0 60 70 40 4.24 0.5152 WVFGRD96 87.0 60 70 40 4.24 0.5218 WVFGRD96 88.0 60 70 40 4.24 0.5249 WVFGRD96 89.0 60 70 40 4.25 0.5310 WVFGRD96 90.0 60 65 40 4.23 0.5329 WVFGRD96 91.0 60 70 40 4.25 0.5398 WVFGRD96 92.0 60 65 40 4.24 0.5420 WVFGRD96 93.0 60 65 45 4.23 0.5483 WVFGRD96 94.0 60 65 45 4.24 0.5511 WVFGRD96 95.0 60 65 45 4.24 0.5575 WVFGRD96 96.0 60 65 45 4.24 0.5592 WVFGRD96 97.0 60 65 45 4.25 0.5652 WVFGRD96 98.0 60 65 45 4.25 0.5670 WVFGRD96 99.0 60 65 45 4.25 0.5716 WVFGRD96 100.0 60 65 45 4.25 0.5731 WVFGRD96 101.0 60 65 45 4.26 0.5780 WVFGRD96 102.0 60 65 45 4.26 0.5778 WVFGRD96 103.0 60 65 45 4.26 0.5830 WVFGRD96 104.0 60 65 45 4.26 0.5829 WVFGRD96 105.0 60 65 45 4.27 0.5860 WVFGRD96 106.0 60 65 45 4.27 0.5867 WVFGRD96 107.0 60 65 45 4.27 0.5881 WVFGRD96 108.0 60 65 45 4.27 0.5889 WVFGRD96 109.0 60 65 45 4.27 0.5892 WVFGRD96 110.0 60 65 45 4.28 0.5897 WVFGRD96 111.0 60 65 45 4.28 0.5883 WVFGRD96 112.0 55 70 50 4.29 0.5904 WVFGRD96 113.0 55 70 50 4.29 0.5887 WVFGRD96 114.0 55 70 50 4.29 0.5897 WVFGRD96 115.0 55 70 50 4.30 0.5887 WVFGRD96 116.0 55 70 50 4.30 0.5875 WVFGRD96 117.0 55 70 50 4.30 0.5865 WVFGRD96 118.0 55 70 50 4.30 0.5841 WVFGRD96 119.0 55 70 50 4.30 0.5831 WVFGRD96 120.0 55 70 50 4.31 0.5816 WVFGRD96 121.0 55 70 50 4.31 0.5792 WVFGRD96 122.0 50 70 50 4.30 0.5770 WVFGRD96 123.0 55 70 50 4.31 0.5733 WVFGRD96 124.0 50 70 50 4.30 0.5726 WVFGRD96 125.0 50 70 50 4.30 0.5700 WVFGRD96 126.0 50 70 50 4.30 0.5666 WVFGRD96 127.0 50 70 50 4.30 0.5653 WVFGRD96 128.0 50 70 50 4.31 0.5605 WVFGRD96 129.0 50 70 50 4.31 0.5592
The best solution is
WVFGRD96 112.0 55 70 50 4.29 0.5904
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 0.10 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: