2016/08/26 20:49:12 42.794 13.1532 10.1 3.2 Perugia
USGS Felt map for this earthquake
SLU Moment Tensor Solution ENS 2016/08/26 20:49:12:3 42.79 13.15 10.1 3.2 Perugia Stations used: IV.ARCI IV.ARVD IV.ASQU IV.ASSB IV.ATTE IV.CESX IV.CING IV.CRE IV.CSNT IV.FDMO IV.GUMA IV.LPEL IV.MGAB IV.OFFI IV.OSSC IV.PARC IV.PIEI IV.PTQR IV.RMP IV.SACS IV.SNTG IV.TERO IV.TOLF Filtering commands used: cut o DIST/3.3 -20 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.10 n 3 Best Fitting Double Couple Mo = 5.07e+20 dyne-cm Mw = 3.07 Z = 5 km Plane Strike Dip Rake NP1 355 65 -70 NP2 134 32 -126 Principal Axes: Axis Value Plunge Azimuth T 5.07e+20 18 70 N 0.00e+00 18 166 P -5.07e+20 64 299 Moment Tensor: (dyne-cm) Component Value Mxx 3.01e+19 Mxy 1.86e+20 Mxz -4.63e+19 Myy 3.35e+20 Myz 3.11e+20 Mzz -3.65e+20 ------######## ------------########## ----------------############ ------------------############ #--------------------############# ##--------------------############## ##----------------------########## # ###----------------------########## T ## ###---------- ----------######### ## ####---------- P ----------############### #####--------- ----------############### #####----------------------############### ######----------------------############## ######--------------------############## #######-------------------############## #######------------------############# ########----------------############ #########--------------########### ##########----------########## #############------#######-- ###############------- ##########---- Global CMT Convention Moment Tensor: R T P -3.65e+20 -4.63e+19 -3.11e+20 -4.63e+19 3.01e+19 -1.86e+20 -3.11e+20 -1.86e+20 3.35e+20 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20160826204912/index.html |
STK = -5 DIP = 65 RAKE = -70 MW = 3.07 HS = 5.0
The NDK file is 20160826204912.ndk The waveform inversion is preferred.
The following compares this source inversion to others
SLU Moment Tensor Solution ENS 2016/08/26 20:49:12:3 42.79 13.15 10.1 3.2 Perugia Stations used: IV.ARCI IV.ARVD IV.ASQU IV.ASSB IV.ATTE IV.CESX IV.CING IV.CRE IV.CSNT IV.FDMO IV.GUMA IV.LPEL IV.MGAB IV.OFFI IV.OSSC IV.PARC IV.PIEI IV.PTQR IV.RMP IV.SACS IV.SNTG IV.TERO IV.TOLF Filtering commands used: cut o DIST/3.3 -20 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.10 n 3 Best Fitting Double Couple Mo = 5.07e+20 dyne-cm Mw = 3.07 Z = 5 km Plane Strike Dip Rake NP1 355 65 -70 NP2 134 32 -126 Principal Axes: Axis Value Plunge Azimuth T 5.07e+20 18 70 N 0.00e+00 18 166 P -5.07e+20 64 299 Moment Tensor: (dyne-cm) Component Value Mxx 3.01e+19 Mxy 1.86e+20 Mxz -4.63e+19 Myy 3.35e+20 Myz 3.11e+20 Mzz -3.65e+20 ------######## ------------########## ----------------############ ------------------############ #--------------------############# ##--------------------############## ##----------------------########## # ###----------------------########## T ## ###---------- ----------######### ## ####---------- P ----------############### #####--------- ----------############### #####----------------------############### ######----------------------############## ######--------------------############## #######-------------------############## #######------------------############# ########----------------############ #########--------------########### ##########----------########## #############------#######-- ###############------- ##########---- Global CMT Convention Moment Tensor: R T P -3.65e+20 -4.63e+19 -3.11e+20 -4.63e+19 3.01e+19 -1.86e+20 -3.11e+20 -1.86e+20 3.35e+20 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20160826204912/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 +50 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 5 65 -65 2.87 0.4300 WVFGRD96 2.0 0 75 -70 2.97 0.4887 WVFGRD96 3.0 0 70 -65 2.97 0.5541 WVFGRD96 4.0 -5 65 -65 2.98 0.5817 WVFGRD96 5.0 -5 65 -70 3.07 0.6052 WVFGRD96 6.0 0 70 -65 3.05 0.5897 WVFGRD96 7.0 5 70 -55 3.04 0.5650 WVFGRD96 8.0 15 85 -40 3.00 0.5399 WVFGRD96 9.0 195 90 40 3.01 0.5236 WVFGRD96 10.0 195 90 40 3.02 0.5065 WVFGRD96 11.0 195 90 40 3.02 0.4887 WVFGRD96 12.0 195 90 40 3.03 0.4724 WVFGRD96 13.0 200 80 40 3.04 0.4563 WVFGRD96 14.0 200 80 35 3.06 0.4398 WVFGRD96 15.0 200 80 40 3.08 0.4212 WVFGRD96 16.0 195 85 40 3.08 0.4047 WVFGRD96 17.0 200 75 40 3.09 0.3896 WVFGRD96 18.0 200 75 40 3.10 0.3747 WVFGRD96 19.0 200 75 45 3.10 0.3607 WVFGRD96 20.0 200 75 45 3.11 0.3480 WVFGRD96 21.0 200 75 40 3.12 0.3352 WVFGRD96 22.0 200 75 40 3.13 0.3230 WVFGRD96 23.0 195 80 40 3.13 0.3127 WVFGRD96 24.0 20 80 -30 3.15 0.3029 WVFGRD96 25.0 315 45 45 3.14 0.2994 WVFGRD96 26.0 315 45 45 3.15 0.3021 WVFGRD96 27.0 315 45 50 3.16 0.3020 WVFGRD96 28.0 315 45 50 3.17 0.2986 WVFGRD96 29.0 320 45 55 3.19 0.2926
The best solution is
WVFGRD96 5.0 -5 65 -70 3.07 0.6052
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 +50 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=Fri Aug 26 16:31:15 CDT 2016