USGS/SLU Moment Tensor Solution ENS 2018/08/24 06:56:51:0 36.93 -104.86 6.5 3.6 New Mexico Stations used: IU.ANMO IW.SMCO N4.KSCO N4.MSTX TA.Q24A TA.S22A TA.T25A TA.Y22D TX.RTBA US.AMTX US.MVCO US.SDCO YX.UNM5 Filtering commands used: cut o DIST/3.3 -30 o DIST/3.3 +40 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.10 n 3 Best Fitting Double Couple Mo = 2.66e+21 dyne-cm Mw = 3.55 Z = 8 km Plane Strike Dip Rake NP1 145 65 -85 NP2 313 25 -101 Principal Axes: Axis Value Plunge Azimuth T 2.66e+21 20 231 N 0.00e+00 5 323 P -2.66e+21 70 65 Moment Tensor: (dyne-cm) Component Value Mxx 8.66e+20 Mxy 1.03e+21 Mxz -8.97e+20 Myy 1.16e+21 Myz -1.45e+21 Mzz -2.03e+21 ############## ###################### ------------------########## ###--------------------####### #####----------------------####### ######------------------------###### ########------------------------###### ##########-------------------------##### ##########-------------- ---------#### ############------------- P ---------##### #############------------ ----------#### ##############------------------------#### ###############------------------------### ###############-----------------------## #################---------------------## #### ###########------------------## ### T ############-----------------# ## ##############--------------# ####################---------- ######################------ ###################### ############## Global CMT Convention Moment Tensor: R T P -2.03e+21 -8.97e+20 1.45e+21 -8.97e+20 8.66e+20 -1.03e+21 1.45e+21 -1.03e+21 1.16e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20180824065651/index.html |
STK = 145 DIP = 65 RAKE = -85 MW = 3.55 HS = 8.0
The NDK file is 20180824065651.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2018/08/24 06:56:51:0 36.93 -104.86 6.5 3.6 New Mexico Stations used: IU.ANMO IW.SMCO N4.KSCO N4.MSTX TA.Q24A TA.S22A TA.T25A TA.Y22D TX.RTBA US.AMTX US.MVCO US.SDCO YX.UNM5 Filtering commands used: cut o DIST/3.3 -30 o DIST/3.3 +40 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.10 n 3 Best Fitting Double Couple Mo = 2.66e+21 dyne-cm Mw = 3.55 Z = 8 km Plane Strike Dip Rake NP1 145 65 -85 NP2 313 25 -101 Principal Axes: Axis Value Plunge Azimuth T 2.66e+21 20 231 N 0.00e+00 5 323 P -2.66e+21 70 65 Moment Tensor: (dyne-cm) Component Value Mxx 8.66e+20 Mxy 1.03e+21 Mxz -8.97e+20 Myy 1.16e+21 Myz -1.45e+21 Mzz -2.03e+21 ############## ###################### ------------------########## ###--------------------####### #####----------------------####### ######------------------------###### ########------------------------###### ##########-------------------------##### ##########-------------- ---------#### ############------------- P ---------##### #############------------ ----------#### ##############------------------------#### ###############------------------------### ###############-----------------------## #################---------------------## #### ###########------------------## ### T ############-----------------# ## ##############--------------# ####################---------- ######################------ ###################### ############## Global CMT Convention Moment Tensor: R T P -2.03e+21 -8.97e+20 1.45e+21 -8.97e+20 8.66e+20 -1.03e+21 1.45e+21 -1.03e+21 1.16e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20180824065651/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:
cut o DIST/3.3 -30 o DIST/3.3 +40 rtr taper w 0.1 hp c 0.03 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 1.0 355 50 -25 3.12 0.2558 WVFGRD96 2.0 330 30 -70 3.35 0.3727 WVFGRD96 3.0 345 20 -50 3.41 0.4840 WVFGRD96 4.0 325 20 -80 3.43 0.6088 WVFGRD96 5.0 150 70 -80 3.45 0.6869 WVFGRD96 6.0 150 70 -75 3.45 0.7349 WVFGRD96 7.0 145 65 -80 3.47 0.7629 WVFGRD96 8.0 145 65 -85 3.55 0.7882 WVFGRD96 9.0 145 65 -80 3.55 0.7860 WVFGRD96 10.0 145 65 -80 3.56 0.7751 WVFGRD96 11.0 160 75 -65 3.56 0.7614 WVFGRD96 12.0 165 80 -60 3.57 0.7467 WVFGRD96 13.0 165 85 -60 3.57 0.7325 WVFGRD96 14.0 350 90 55 3.59 0.7197 WVFGRD96 15.0 165 85 -60 3.59 0.7071 WVFGRD96 16.0 165 90 -60 3.60 0.6981 WVFGRD96 17.0 350 85 60 3.61 0.6865 WVFGRD96 18.0 350 85 60 3.62 0.6759 WVFGRD96 19.0 345 85 65 3.62 0.6635 WVFGRD96 20.0 350 80 65 3.64 0.6533 WVFGRD96 21.0 350 80 70 3.66 0.6423 WVFGRD96 22.0 350 80 70 3.66 0.6293 WVFGRD96 23.0 350 75 75 3.68 0.6198 WVFGRD96 24.0 350 75 80 3.69 0.6088 WVFGRD96 25.0 345 75 80 3.69 0.6007 WVFGRD96 26.0 350 70 85 3.71 0.5918 WVFGRD96 27.0 350 70 85 3.72 0.5805 WVFGRD96 28.0 175 20 95 3.73 0.5665 WVFGRD96 29.0 40 40 30 3.69 0.5515
The best solution is
WVFGRD96 8.0 145 65 -85 3.55 0.7882
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
cut o DIST/3.3 -30 o DIST/3.3 +40 rtr taper w 0.1 hp c 0.03 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: