2011/03/13 20:16:21 32.9540 -100.8100 5.0 3.80
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution ENS 2011/03/13 20:16:21:0 32.95 -100.81 5.0 3.8 Stations used: IU.ANMO TA.133A TA.134A TA.135A TA.233A TA.234A TA.333A TA.334A TA.433A TA.ABTX TA.MSTX TA.S30A TA.TUL1 TA.V32A TA.V36A TA.X34A TA.X35A TA.Y33A TA.Y34A TA.Y35A TA.Y36A TA.Y37A TA.Z33A TA.Z34A TA.Z35A TA.Z36A TA.Z37A US.AMTX US.JCT US.MNTX Filtering commands used: hp c 0.02 n 3 lp c 0.10 n 3 br c 0.12 0.25 n 4 p 2 Best Fitting Double Couple Mo = 6.53e+21 dyne-cm Mw = 3.81 Z = 2 km Plane Strike Dip Rake NP1 70 60 -50 NP2 191 48 -138 Principal Axes: Axis Value Plunge Azimuth T 6.53e+21 7 133 N 0.00e+00 34 227 P -6.53e+21 55 33 Moment Tensor: (dyne-cm) Component Value Mxx 1.49e+21 Mxy -4.18e+21 Mxz -3.07e+21 Myy 2.84e+21 Myz -1.12e+21 Mzz -4.33e+21 #########----- ##########------------ ###########----------------- ##########-------------------- ###########----------------------- ###########------------------------- ###########----------- ------------- ###########------------ P -------------# ##########------------- ------------## ###########---------------------------#### ###########-------------------------###### ##########-------------------------####### ##########----------------------########## #########-------------------############ #########---------------################ --#######---------#################### --------############################ --------###################### # ------###################### T ------##################### ----################## --############ Global CMT Convention Moment Tensor: R T P -4.33e+21 -3.07e+21 1.12e+21 -3.07e+21 1.49e+21 4.18e+21 1.12e+21 4.18e+21 2.84e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20110313201621/index.html |
STK = 70 DIP = 60 RAKE = -50 MW = 3.81 HS = 2.0
The NDK file is 20110313201621.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2011/03/13 20:16:21:0 32.95 -100.81 5.0 3.8 Stations used: IU.ANMO TA.133A TA.134A TA.135A TA.233A TA.234A TA.333A TA.334A TA.433A TA.ABTX TA.MSTX TA.S30A TA.TUL1 TA.V32A TA.V36A TA.X34A TA.X35A TA.Y33A TA.Y34A TA.Y35A TA.Y36A TA.Y37A TA.Z33A TA.Z34A TA.Z35A TA.Z36A TA.Z37A US.AMTX US.JCT US.MNTX Filtering commands used: hp c 0.02 n 3 lp c 0.10 n 3 br c 0.12 0.25 n 4 p 2 Best Fitting Double Couple Mo = 6.53e+21 dyne-cm Mw = 3.81 Z = 2 km Plane Strike Dip Rake NP1 70 60 -50 NP2 191 48 -138 Principal Axes: Axis Value Plunge Azimuth T 6.53e+21 7 133 N 0.00e+00 34 227 P -6.53e+21 55 33 Moment Tensor: (dyne-cm) Component Value Mxx 1.49e+21 Mxy -4.18e+21 Mxz -3.07e+21 Myy 2.84e+21 Myz -1.12e+21 Mzz -4.33e+21 #########----- ##########------------ ###########----------------- ##########-------------------- ###########----------------------- ###########------------------------- ###########----------- ------------- ###########------------ P -------------# ##########------------- ------------## ###########---------------------------#### ###########-------------------------###### ##########-------------------------####### ##########----------------------########## #########-------------------############ #########---------------################ --#######---------#################### --------############################ --------###################### # ------###################### T ------##################### ----################## --############ Global CMT Convention Moment Tensor: R T P -4.33e+21 -3.07e+21 1.12e+21 -3.07e+21 1.49e+21 4.18e+21 1.12e+21 4.18e+21 2.84e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20110313201621/index.html |
(a) mLg computed using the IASPEI formula; (b) mLg residuals ; the values used for the trimmed mean are indicated.
(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 3 br c 0.12 0.25 n 4 p 2The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT WVFGRD96 0.5 75 65 -40 3.72 0.3532 WVFGRD96 1.0 75 65 -40 3.75 0.3882 WVFGRD96 2.0 70 60 -50 3.81 0.4028 WVFGRD96 3.0 250 50 -45 3.84 0.3880 WVFGRD96 4.0 70 70 -55 3.87 0.3695 WVFGRD96 5.0 80 85 -45 3.85 0.3612 WVFGRD96 6.0 270 65 25 3.81 0.3644 WVFGRD96 7.0 270 70 30 3.82 0.3695 WVFGRD96 8.0 270 70 30 3.83 0.3733 WVFGRD96 9.0 270 70 30 3.83 0.3756 WVFGRD96 10.0 270 70 35 3.86 0.3733 WVFGRD96 11.0 270 70 35 3.86 0.3742 WVFGRD96 12.0 270 70 35 3.87 0.3741 WVFGRD96 13.0 270 70 35 3.88 0.3734 WVFGRD96 14.0 270 70 35 3.88 0.3722 WVFGRD96 15.0 270 70 35 3.89 0.3704 WVFGRD96 16.0 270 70 35 3.90 0.3683 WVFGRD96 17.0 270 70 35 3.91 0.3658 WVFGRD96 18.0 270 70 35 3.91 0.3629 WVFGRD96 19.0 270 70 40 3.93 0.3597 WVFGRD96 20.0 275 65 45 3.95 0.3559 WVFGRD96 21.0 275 65 45 3.96 0.3523 WVFGRD96 22.0 275 65 50 3.98 0.3485 WVFGRD96 23.0 275 65 50 3.99 0.3445 WVFGRD96 24.0 275 65 50 4.00 0.3402 WVFGRD96 25.0 275 65 50 4.00 0.3356 WVFGRD96 26.0 275 65 50 4.01 0.3304 WVFGRD96 27.0 275 65 55 4.03 0.3252 WVFGRD96 28.0 275 65 55 4.04 0.3197 WVFGRD96 29.0 275 65 55 4.04 0.3136
The best solution is
WVFGRD96 2.0 70 60 -50 3.81 0.4028
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 br c 0.12 0.25 n 4 p 2
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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 CUS model used for the waveform synthetic seismograms and for the surface wave eigenfunctions and dispersion is as follows:
MODEL.01 CUS Model with Q from simple gamma values 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 1.0000 5.0000 2.8900 2.5000 0.172E-02 0.387E-02 0.00 0.00 1.00 1.00 9.0000 6.1000 3.5200 2.7300 0.160E-02 0.363E-02 0.00 0.00 1.00 1.00 10.0000 6.4000 3.7000 2.8200 0.149E-02 0.336E-02 0.00 0.00 1.00 1.00 20.0000 6.7000 3.8700 2.9020 0.000E-04 0.000E-04 0.00 0.00 1.00 1.00 0.0000 8.1500 4.7000 3.3640 0.194E-02 0.431E-02 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: