2011/10/30 14:40:32 42.274 13.323 8.2 3.6 Italy
USGS Felt map for this earthquake
SLU Moment Tensor Solution ENS 2011/10/30 14:40:32:0 42.27 13.32 8.2 3.6 Italy Stations used: IV.CAFR IV.CERT IV.CESI IV.CESX IV.CING IV.FAGN IV.FDMO IV.FIAM IV.FRES IV.GIUL IV.GUMA IV.LATE IV.MA9 IV.MGAB IV.MIDA IV.MODR IV.MTCE IV.MURB IV.NRCA IV.POFI IV.PTQR IV.RDP IV.RMP IV.RNI2 IV.ROM9 IV.SACS IV.SAMA IV.SNTG IV.SSFR IV.TERO IV.TOLF IV.TRTR IV.VVLD MN.AQU Filtering commands used: hp c 0.02 n 3 lp c 0.10 n 3 Best Fitting Double Couple Mo = 2.75e+21 dyne-cm Mw = 3.56 Z = 1 km Plane Strike Dip Rake NP1 138 50 -94 NP2 325 40 -85 Principal Axes: Axis Value Plunge Azimuth T 2.75e+21 5 231 N 0.00e+00 3 141 P -2.75e+21 84 19 Moment Tensor: (dyne-cm) Component Value Mxx 1.03e+21 Mxy 1.32e+21 Mxz -4.24e+20 Myy 1.67e+21 Myz -2.85e+20 Mzz -2.70e+21 ############## ###################### --------------############## #-----------------############ ###--------------------########### ###-----------------------########## #####-----------------------########## ######-------------------------######### ######--------------------------######## ########------------ -----------######## #########----------- P -----------######## ##########---------- ------------####### ###########------------------------####### ###########------------------------##### ############-----------------------##### #############---------------------#### # ##########------------------#### T #############---------------### ################-----------## #######################----- ###################### ############## Global CMT Convention Moment Tensor: R T P -2.70e+21 -4.24e+20 2.85e+20 -4.24e+20 1.03e+21 -1.32e+21 2.85e+20 -1.32e+21 1.67e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20111030144032/index.html |
STK = 325 DIP = 40 RAKE = -85 MW = 3.56 HS = 1.0
The waveform inversion is preferred.
The following compares this source inversion to others
SLU Moment Tensor Solution ENS 2011/10/30 14:40:32:0 42.27 13.32 8.2 3.6 Italy Stations used: IV.CAFR IV.CERT IV.CESI IV.CESX IV.CING IV.FAGN IV.FDMO IV.FIAM IV.FRES IV.GIUL IV.GUMA IV.LATE IV.MA9 IV.MGAB IV.MIDA IV.MODR IV.MTCE IV.MURB IV.NRCA IV.POFI IV.PTQR IV.RDP IV.RMP IV.RNI2 IV.ROM9 IV.SACS IV.SAMA IV.SNTG IV.SSFR IV.TERO IV.TOLF IV.TRTR IV.VVLD MN.AQU Filtering commands used: hp c 0.02 n 3 lp c 0.10 n 3 Best Fitting Double Couple Mo = 2.75e+21 dyne-cm Mw = 3.56 Z = 1 km Plane Strike Dip Rake NP1 138 50 -94 NP2 325 40 -85 Principal Axes: Axis Value Plunge Azimuth T 2.75e+21 5 231 N 0.00e+00 3 141 P -2.75e+21 84 19 Moment Tensor: (dyne-cm) Component Value Mxx 1.03e+21 Mxy 1.32e+21 Mxz -4.24e+20 Myy 1.67e+21 Myz -2.85e+20 Mzz -2.70e+21 ############## ###################### --------------############## #-----------------############ ###--------------------########### ###-----------------------########## #####-----------------------########## ######-------------------------######### ######--------------------------######## ########------------ -----------######## #########----------- P -----------######## ##########---------- ------------####### ###########------------------------####### ###########------------------------##### ############-----------------------##### #############---------------------#### # ##########------------------#### T #############---------------### ################-----------## #######################----- ###################### ############## Global CMT Convention Moment Tensor: R T P -2.70e+21 -4.24e+20 2.85e+20 -4.24e+20 1.03e+21 -1.32e+21 2.85e+20 -1.32e+21 1.67e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20111030144032/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:
hp c 0.02 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 1.0 325 40 -85 3.56 0.5252 WVFGRD96 2.0 330 35 -75 3.61 0.4894 WVFGRD96 3.0 335 20 -70 3.61 0.4274 WVFGRD96 4.0 335 20 -70 3.59 0.4413 WVFGRD96 5.0 330 20 -75 3.69 0.4624 WVFGRD96 6.0 135 70 -95 3.69 0.4615 WVFGRD96 7.0 140 70 -90 3.70 0.4512 WVFGRD96 8.0 140 75 -75 3.64 0.4331 WVFGRD96 9.0 140 75 -75 3.64 0.4187 WVFGRD96 10.0 10 65 40 3.68 0.4098 WVFGRD96 11.0 315 70 75 3.66 0.4026 WVFGRD96 12.0 315 65 80 3.68 0.4038 WVFGRD96 13.0 320 60 80 3.70 0.4038 WVFGRD96 14.0 320 60 85 3.71 0.4029 WVFGRD96 15.0 320 60 85 3.75 0.3955 WVFGRD96 16.0 320 60 85 3.76 0.3895 WVFGRD96 17.0 320 60 85 3.77 0.3800 WVFGRD96 18.0 315 55 80 3.78 0.3713 WVFGRD96 19.0 315 55 80 3.79 0.3600 WVFGRD96 20.0 315 55 80 3.80 0.3470 WVFGRD96 21.0 310 55 75 3.80 0.3329 WVFGRD96 22.0 310 55 75 3.81 0.3188 WVFGRD96 23.0 315 50 80 3.81 0.3044 WVFGRD96 24.0 150 40 100 3.81 0.2905 WVFGRD96 25.0 155 50 110 3.82 0.2785 WVFGRD96 26.0 305 45 70 3.82 0.2709 WVFGRD96 27.0 300 45 65 3.83 0.2639 WVFGRD96 28.0 150 55 -70 3.84 0.2532 WVFGRD96 29.0 145 50 -80 3.85 0.2479
The best solution is
WVFGRD96 1.0 325 40 -85 3.56 0.5252
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
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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=Wed Nov 2 19:32:22 CDT 2011