2011/12/03 09:33:59 61.979 -150.990 10 4.40 Alaska
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution ENS 2011/12/03 09:33:59:0 61.98 -150.99 10.0 4.4 Alaska Stations used: AK.BMR AK.BPAW AK.CAST AK.CCB AK.DHY AK.DIV AK.DOT AK.EYAK AK.FIB AK.FID AK.FYU AK.GLI AK.HDA AK.HMT AK.KLU AK.KNK AK.KTH AK.MCK AK.MDM AK.MLY AK.PAX AK.PPLA AK.RAG AK.RC01 AK.RND AK.SAW AK.SCM AK.SGA AK.SKN AK.SSN AK.SWD AK.TRF AK.WAX AK.WRH AT.MENT AT.PMR AT.SVW2 IU.COLA US.EGAK Filtering commands used: hp c 0.02 n 3 lp c 0.06 n 3 Best Fitting Double Couple Mo = 2.43e+22 dyne-cm Mw = 4.19 Z = 20 km Plane Strike Dip Rake NP1 360 60 75 NP2 208 33 114 Principal Axes: Axis Value Plunge Azimuth T 2.43e+22 71 236 N 0.00e+00 13 8 P -2.43e+22 14 101 Moment Tensor: (dyne-cm) Component Value Mxx -0.00e+00 Mxy 5.44e+21 Mxz -3.14e+21 Myy -2.03e+22 Myz -1.17e+22 Mzz 2.03e+22 --------###### -----------###-------- ----------########---------- ---------###########---------- ---------##############----------- --------################------------ --------##################------------ --------###################------------- -------####################------------- -------######################------------- -------######################------------- ------######### ###########-------- -- ------######### T ###########-------- P -- -----######### ##########--------- - -----######################------------- ----######################------------ ----####################------------ ---####################----------- --##################---------- --################---------- -#############-------- ########------ Global CMT Convention Moment Tensor: R T P 2.03e+22 -3.14e+21 1.17e+22 -3.14e+21 -0.00e+00 -5.44e+21 1.17e+22 -5.44e+21 -2.03e+22 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20111203093359/index.html |
STK = 0 DIP = 60 RAKE = 75 MW = 4.19 HS = 20.0
The NDK file is 20111203093359.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2011/12/03 09:33:59:0 61.98 -150.99 10.0 4.4 Alaska Stations used: AK.BMR AK.BPAW AK.CAST AK.CCB AK.DHY AK.DIV AK.DOT AK.EYAK AK.FIB AK.FID AK.FYU AK.GLI AK.HDA AK.HMT AK.KLU AK.KNK AK.KTH AK.MCK AK.MDM AK.MLY AK.PAX AK.PPLA AK.RAG AK.RC01 AK.RND AK.SAW AK.SCM AK.SGA AK.SKN AK.SSN AK.SWD AK.TRF AK.WAX AK.WRH AT.MENT AT.PMR AT.SVW2 IU.COLA US.EGAK Filtering commands used: hp c 0.02 n 3 lp c 0.06 n 3 Best Fitting Double Couple Mo = 2.43e+22 dyne-cm Mw = 4.19 Z = 20 km Plane Strike Dip Rake NP1 360 60 75 NP2 208 33 114 Principal Axes: Axis Value Plunge Azimuth T 2.43e+22 71 236 N 0.00e+00 13 8 P -2.43e+22 14 101 Moment Tensor: (dyne-cm) Component Value Mxx -0.00e+00 Mxy 5.44e+21 Mxz -3.14e+21 Myy -2.03e+22 Myz -1.17e+22 Mzz 2.03e+22 --------###### -----------###-------- ----------########---------- ---------###########---------- ---------##############----------- --------################------------ --------##################------------ --------###################------------- -------####################------------- -------######################------------- -------######################------------- ------######### ###########-------- -- ------######### T ###########-------- P -- -----######### ##########--------- - -----######################------------- ----######################------------ ----####################------------ ---####################----------- --##################---------- --################---------- -#############-------- ########------ Global CMT Convention Moment Tensor: R T P 2.03e+22 -3.14e+21 1.17e+22 -3.14e+21 -0.00e+00 -5.44e+21 1.17e+22 -5.44e+21 -2.03e+22 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20111203093359/index.html |
USGS/SLU Regional Moment Solution 11/12/03 09:33:59.00 Epicenter: 61.979 -150.990 MW 4.2 USGS/SLU REGIONAL MOMENT TENSOR Depth 21 No. of sta: 78 Moment Tensor; Scale 10**15 Nm Mrr= 0.78 Mtt=-0.10 Mpp=-0.68 Mrt=-1.15 Mrp= 1.82 Mtp=-1.04 Principal axes: T Val= 2.82 Plg=46 Azm=228 N -0.87 29 353 P -1.94 30 101 Best Double Couple:Mo=2.5*10**15 NP1:Strike=348 Dip=81 Slip= 61 NP2: 242 31 162 |
(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 15 45 -90 3.78 0.3741 WVFGRD96 1.0 200 45 -90 3.81 0.3537 WVFGRD96 2.0 20 45 -90 3.90 0.4177 WVFGRD96 3.0 20 50 -90 3.94 0.3394 WVFGRD96 4.0 40 70 -65 3.94 0.2781 WVFGRD96 5.0 140 30 -15 3.94 0.3091 WVFGRD96 6.0 130 25 -15 3.95 0.3504 WVFGRD96 7.0 135 25 -5 3.95 0.3902 WVFGRD96 8.0 135 20 0 4.03 0.4199 WVFGRD96 9.0 145 20 15 4.03 0.4588 WVFGRD96 10.0 195 15 95 4.08 0.5061 WVFGRD96 11.0 5 70 85 4.11 0.5530 WVFGRD96 12.0 200 25 105 4.14 0.5969 WVFGRD96 13.0 5 65 85 4.14 0.6358 WVFGRD96 14.0 5 60 85 4.16 0.6663 WVFGRD96 15.0 5 60 80 4.16 0.6923 WVFGRD96 16.0 5 60 80 4.17 0.7107 WVFGRD96 17.0 5 60 80 4.17 0.7227 WVFGRD96 18.0 5 60 80 4.18 0.7299 WVFGRD96 19.0 0 60 75 4.19 0.7330 WVFGRD96 20.0 0 60 75 4.19 0.7332 WVFGRD96 21.0 0 60 75 4.20 0.7299 WVFGRD96 22.0 0 60 75 4.20 0.7256 WVFGRD96 23.0 0 60 75 4.21 0.7192 WVFGRD96 24.0 5 60 75 4.21 0.7115 WVFGRD96 25.0 5 60 75 4.21 0.7023 WVFGRD96 26.0 0 60 70 4.22 0.6923 WVFGRD96 27.0 0 60 70 4.22 0.6812 WVFGRD96 28.0 0 60 70 4.23 0.6686 WVFGRD96 29.0 0 60 70 4.23 0.6547
The best solution is
WVFGRD96 20.0 0 60 75 4.19 0.7332
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: