2011/01/23 02:50:04 63.5230 -150.8060 12.3 5.00
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution ENS 2011/01/23 02:50:04:0 63.52 -150.81 12.3 5.0 Stations used: AK.BPAW AK.CAST AK.CCB AK.COLD AK.DHY AK.DIV AK.DOT AK.FID AK.HDA AK.KLU AK.MCK AK.MDM AK.MLY AK.PAX AK.PPLA AK.RC01 AK.RND AK.SAW AK.SCM AK.SWD AK.WRH AT.MENT AT.SVW2 AT.TTA IU.COLA Filtering commands used: hp c 0.02 n 3 lp c 0.0625 n 3 Best Fitting Double Couple Mo = 5.25e+23 dyne-cm Mw = 5.08 Z = 16 km Plane Strike Dip Rake NP1 185 90 -10 NP2 275 80 -180 Principal Axes: Axis Value Plunge Azimuth T 5.25e+23 7 230 N 0.00e+00 80 5 P -5.25e+23 7 140 Moment Tensor: (dyne-cm) Component Value Mxx -8.97e+22 Mxy 5.09e+23 Mxz 7.94e+21 Myy 8.97e+22 Myz -9.08e+22 Mzz 7.97e+15 ---------##### -------------######### ---------------############# ----------------############## ------------------################ -------------------################# --------------------################## ---------------------################### --------------------#################### -------###########---##################### #####################------------######### #####################------------------### #####################--------------------- ####################-------------------- ###################--------------------- ##################-------------------- # #############------------------- T #############------------- -- #############------------- P #############------------- #########------------- #####--------- Global CMT Convention Moment Tensor: R T P 7.97e+15 7.94e+21 9.08e+22 7.94e+21 -8.97e+22 -5.09e+23 9.08e+22 -5.09e+23 8.97e+22 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20110123025004/index.html |
STK = 185 DIP = 90 RAKE = -10 MW = 5.08 HS = 16.0
The NDK file is 20110123025004.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2011/01/23 02:50:04:0 63.52 -150.81 12.3 5.0 Stations used: AK.BPAW AK.CAST AK.CCB AK.COLD AK.DHY AK.DIV AK.DOT AK.FID AK.HDA AK.KLU AK.MCK AK.MDM AK.MLY AK.PAX AK.PPLA AK.RC01 AK.RND AK.SAW AK.SCM AK.SWD AK.WRH AT.MENT AT.SVW2 AT.TTA IU.COLA Filtering commands used: hp c 0.02 n 3 lp c 0.0625 n 3 Best Fitting Double Couple Mo = 5.25e+23 dyne-cm Mw = 5.08 Z = 16 km Plane Strike Dip Rake NP1 185 90 -10 NP2 275 80 -180 Principal Axes: Axis Value Plunge Azimuth T 5.25e+23 7 230 N 0.00e+00 80 5 P -5.25e+23 7 140 Moment Tensor: (dyne-cm) Component Value Mxx -8.97e+22 Mxy 5.09e+23 Mxz 7.94e+21 Myy 8.97e+22 Myz -9.08e+22 Mzz 7.97e+15 ---------##### -------------######### ---------------############# ----------------############## ------------------################ -------------------################# --------------------################## ---------------------################### --------------------#################### -------###########---##################### #####################------------######### #####################------------------### #####################--------------------- ####################-------------------- ###################--------------------- ##################-------------------- # #############------------------- T #############------------- -- #############------------- P #############------------- #########------------- #####--------- Global CMT Convention Moment Tensor: R T P 7.97e+15 7.94e+21 9.08e+22 7.94e+21 -8.97e+22 -5.09e+23 9.08e+22 -5.09e+23 8.97e+22 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20110123025004/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.
|
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 0.0625 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 10 70 25 4.62 0.2851 WVFGRD96 1.0 5 80 15 4.62 0.3125 WVFGRD96 2.0 5 75 20 4.76 0.4278 WVFGRD96 3.0 185 75 20 4.81 0.4763 WVFGRD96 4.0 185 80 20 4.84 0.5171 WVFGRD96 5.0 185 90 -20 4.87 0.5499 WVFGRD96 6.0 5 80 20 4.91 0.5907 WVFGRD96 7.0 180 85 -20 4.93 0.6259 WVFGRD96 8.0 185 90 -20 4.97 0.6621 WVFGRD96 9.0 180 80 -20 4.99 0.6934 WVFGRD96 10.0 180 80 -20 5.01 0.7193 WVFGRD96 11.0 180 80 -20 5.02 0.7391 WVFGRD96 12.0 185 85 -15 5.04 0.7520 WVFGRD96 13.0 185 85 -15 5.05 0.7617 WVFGRD96 14.0 185 85 -15 5.06 0.7674 WVFGRD96 15.0 185 90 -10 5.07 0.7694 WVFGRD96 16.0 185 90 -10 5.08 0.7698 WVFGRD96 17.0 185 90 -10 5.09 0.7672 WVFGRD96 18.0 185 90 -10 5.10 0.7628 WVFGRD96 19.0 185 90 -10 5.10 0.7567 WVFGRD96 20.0 185 90 -10 5.11 0.7494 WVFGRD96 21.0 185 90 -10 5.12 0.7412 WVFGRD96 22.0 185 90 -10 5.12 0.7319 WVFGRD96 23.0 185 90 -10 5.13 0.7218 WVFGRD96 24.0 185 90 -10 5.13 0.7111 WVFGRD96 25.0 185 90 -10 5.14 0.6999 WVFGRD96 26.0 185 90 -5 5.14 0.6884 WVFGRD96 27.0 185 90 -5 5.15 0.6774 WVFGRD96 28.0 5 85 5 5.16 0.6664 WVFGRD96 29.0 5 85 -5 5.16 0.6547
The best solution is
WVFGRD96 16.0 185 90 -10 5.08 0.7698
The mechanism correspond to the best fit is
|
The best fit as a function of depth is given in the following figure:
|
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 0.0625 n 3
|
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. |
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: