2016/11/03 07:39:07 42.8338 13.121 9.8 3.4
SLU Moment Tensor Solution ENS 2016/11/03 07:39:07:6 42.83 13.12 9.8 3.4 Stations used: IV.ARVD IV.ASSB IV.ATMI IV.ATPC IV.ATTE IV.ATVO IV.CAFI IV.CAMP IV.CERT IV.CING IV.FAGN IV.FIAM IV.GIGS IV.GUMA IV.INTR IV.MGAB IV.MTCE IV.MURB IV.NARO IV.OFFI IV.PIEI IV.PTQR IV.SACS IV.SNTG IV.SRES IV.T1243 IV.TERO IV.TRTR IV.VVLD MN.AQU Filtering commands used: cut o DIST/3.3 -20 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 = 1.33e+21 dyne-cm Mw = 3.35 Z = 6 km Plane Strike Dip Rake NP1 330 55 -90 NP2 150 35 -90 Principal Axes: Axis Value Plunge Azimuth T 1.33e+21 10 60 N 0.00e+00 -0 330 P -1.33e+21 80 240 Moment Tensor: (dyne-cm) Component Value Mxx 3.13e+20 Mxy 5.43e+20 Mxz 2.28e+20 Myy 9.40e+20 Myz 3.95e+20 Mzz -1.25e+21 ############## ---################### ##---------################# ##------------################ ###----------------############# ####-----------------############ T ####--------------------########## # #####---------------------############## #####-----------------------############ ######------------------------############ ######------------ ---------############ #######----------- P ----------########### #######----------- -----------########## #######------------------------######### ########------------------------######## ########-----------------------####### #########---------------------###### #########--------------------##### #########------------------### ###########--------------### #############--------- ############## Global CMT Convention Moment Tensor: R T P -1.25e+21 2.28e+20 -3.95e+20 2.28e+20 3.13e+20 -5.43e+20 -3.95e+20 -5.43e+20 9.40e+20 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20161103073907/index.html |
STK = 150 DIP = 35 RAKE = -90 MW = 3.35 HS = 6.0
The waveform inversion is preferred.
The following compares this source inversion to others
SLU Moment Tensor Solution ENS 2016/11/03 07:39:07:6 42.83 13.12 9.8 3.4 Stations used: IV.ARVD IV.ASSB IV.ATMI IV.ATPC IV.ATTE IV.ATVO IV.CAFI IV.CAMP IV.CERT IV.CING IV.FAGN IV.FIAM IV.GIGS IV.GUMA IV.INTR IV.MGAB IV.MTCE IV.MURB IV.NARO IV.OFFI IV.PIEI IV.PTQR IV.SACS IV.SNTG IV.SRES IV.T1243 IV.TERO IV.TRTR IV.VVLD MN.AQU Filtering commands used: cut o DIST/3.3 -20 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 = 1.33e+21 dyne-cm Mw = 3.35 Z = 6 km Plane Strike Dip Rake NP1 330 55 -90 NP2 150 35 -90 Principal Axes: Axis Value Plunge Azimuth T 1.33e+21 10 60 N 0.00e+00 -0 330 P -1.33e+21 80 240 Moment Tensor: (dyne-cm) Component Value Mxx 3.13e+20 Mxy 5.43e+20 Mxz 2.28e+20 Myy 9.40e+20 Myz 3.95e+20 Mzz -1.25e+21 ############## ---################### ##---------################# ##------------################ ###----------------############# ####-----------------############ T ####--------------------########## # #####---------------------############## #####-----------------------############ ######------------------------############ ######------------ ---------############ #######----------- P ----------########### #######----------- -----------########## #######------------------------######### ########------------------------######## ########-----------------------####### #########---------------------###### #########--------------------##### #########------------------### ###########--------------### #############--------- ############## Global CMT Convention Moment Tensor: R T P -1.25e+21 2.28e+20 -3.95e+20 2.28e+20 3.13e+20 -5.43e+20 -3.95e+20 -5.43e+20 9.40e+20 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20161103073907/index.html |
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 -20 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 0 60 -50 3.08 0.3679 WVFGRD96 2.0 0 65 -55 3.15 0.3887 WVFGRD96 3.0 345 65 -70 3.20 0.4230 WVFGRD96 4.0 335 60 -85 3.25 0.4714 WVFGRD96 5.0 145 30 -100 3.34 0.5334 WVFGRD96 6.0 150 35 -90 3.35 0.5437 WVFGRD96 7.0 150 35 -90 3.34 0.5237 WVFGRD96 8.0 195 75 25 3.25 0.4701 WVFGRD96 9.0 195 75 25 3.26 0.4622 WVFGRD96 10.0 195 75 25 3.27 0.4506 WVFGRD96 11.0 195 75 20 3.28 0.4374 WVFGRD96 12.0 195 75 20 3.29 0.4243 WVFGRD96 13.0 200 75 20 3.29 0.4114 WVFGRD96 14.0 200 75 20 3.30 0.4004 WVFGRD96 15.0 195 75 -20 3.31 0.3861
The best solution is
WVFGRD96 6.0 150 35 -90 3.35 0.5437
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 -20 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.
The nnCIA used for the waveform synthetic seismograms and for the surface wave eigenfunctions and dispersion is as follows:
MODEL.01 C.It. A. Di Luzio et al Earth Plan Lettrs 280 (2009) 1-12 Fig 5. 7-8 MODEL/SURF3 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 1.5000 3.7497 2.1436 2.2753 0.500E-02 0.100E-01 0.00 0.00 1.00 1.00 3.0000 4.9399 2.8210 2.4858 0.500E-02 0.100E-01 0.00 0.00 1.00 1.00 3.0000 6.0129 3.4336 2.7058 0.500E-02 0.100E-01 0.00 0.00 1.00 1.00 7.0000 5.5516 3.1475 2.6093 0.167E-02 0.333E-02 0.00 0.00 1.00 1.00 15.0000 5.8805 3.3583 2.6770 0.167E-02 0.333E-02 0.00 0.00 1.00 1.00 6.0000 7.1059 4.0081 3.0002 0.167E-02 0.333E-02 0.00 0.00 1.00 1.00 8.0000 7.1000 3.9864 3.0120 0.167E-02 0.333E-02 0.00 0.00 1.00 1.00 0.0000 7.9000 4.4036 3.2760 0.167E-02 0.333E-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:
DATE=Thu Nov 3 09:00:11 CDT 2016