2011/07/12 06:53:22 43.920 11.861 7.8 4.0 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution ENS 2011/07/12 06:53:22:0 43.92 11.86 7.8 4.0 Italy Stations used: GU.MAIM GU.POPM IV.ARCI IV.ASQU IV.ATPC IV.ATTE IV.ATVO IV.BDI IV.CAFI IV.CASP IV.CESI IV.CESX IV.CING IV.CRMI IV.CSNT IV.FDMO IV.FNVD IV.FROS IV.FSSB IV.GROG IV.LNSS IV.MCIV IV.MGAB IV.MSSA IV.MTRZ IV.MURB IV.PARC IV.PESA IV.SACS IV.SASS IV.SNTG IV.SSFR IV.TOLF MN.AQU Filtering commands used: hp c 0.02 n 3 lp c 0.10 n 3 Best Fitting Double Couple Mo = 1.17e+22 dyne-cm Mw = 3.98 Z = 2 km Plane Strike Dip Rake NP1 288 61 -96 NP2 120 30 -80 Principal Axes: Axis Value Plunge Azimuth T 1.17e+22 15 23 N 0.00e+00 5 291 P -1.17e+22 74 184 Moment Tensor: (dyne-cm) Component Value Mxx 8.40e+21 Mxy 3.83e+21 Mxz 5.89e+21 Myy 1.62e+21 Myz 1.36e+21 Mzz -1.00e+22 ############## ################ ### ################### T ###### #################### ####### ################################## #################################### -###-------------##################### #-----------------------################ ##--------------------------############ ###-----------------------------########## ###--------------------------------####### ####---------------------------------##### ####--------------- ----------------#### ####-------------- P ------------------# ######------------ ------------------- ######-------------------------------- #######----------------------------- #########------------------------# ##########------------------## ################----######## ###################### ############## Global CMT Convention Moment Tensor: R T P -1.00e+22 5.89e+21 -1.36e+21 5.89e+21 8.40e+21 -3.83e+21 -1.36e+21 -3.83e+21 1.62e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20110712065322/index.html |
STK = 120 DIP = 30 RAKE = -80 MW = 3.98 HS = 2.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2011/07/12 06:53:22:0 43.92 11.86 7.8 4.0 Italy Stations used: GU.MAIM GU.POPM IV.ARCI IV.ASQU IV.ATPC IV.ATTE IV.ATVO IV.BDI IV.CAFI IV.CASP IV.CESI IV.CESX IV.CING IV.CRMI IV.CSNT IV.FDMO IV.FNVD IV.FROS IV.FSSB IV.GROG IV.LNSS IV.MCIV IV.MGAB IV.MSSA IV.MTRZ IV.MURB IV.PARC IV.PESA IV.SACS IV.SASS IV.SNTG IV.SSFR IV.TOLF MN.AQU Filtering commands used: hp c 0.02 n 3 lp c 0.10 n 3 Best Fitting Double Couple Mo = 1.17e+22 dyne-cm Mw = 3.98 Z = 2 km Plane Strike Dip Rake NP1 288 61 -96 NP2 120 30 -80 Principal Axes: Axis Value Plunge Azimuth T 1.17e+22 15 23 N 0.00e+00 5 291 P -1.17e+22 74 184 Moment Tensor: (dyne-cm) Component Value Mxx 8.40e+21 Mxy 3.83e+21 Mxz 5.89e+21 Myy 1.62e+21 Myz 1.36e+21 Mzz -1.00e+22 ############## ################ ### ################### T ###### #################### ####### ################################## #################################### -###-------------##################### #-----------------------################ ##--------------------------############ ###-----------------------------########## ###--------------------------------####### ####---------------------------------##### ####--------------- ----------------#### ####-------------- P ------------------# ######------------ ------------------- ######-------------------------------- #######----------------------------- #########------------------------# ##########------------------## ################----######## ###################### ############## Global CMT Convention Moment Tensor: R T P -1.00e+22 5.89e+21 -1.36e+21 5.89e+21 8.40e+21 -3.83e+21 -1.36e+21 -3.83e+21 1.62e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20110712065322/index.html |
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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 1.0 120 30 -80 3.91 0.4736 WVFGRD96 2.0 120 30 -80 3.98 0.5279 WVFGRD96 3.0 115 30 -90 3.99 0.5201 WVFGRD96 4.0 115 35 -85 3.99 0.4811 WVFGRD96 5.0 115 35 -85 4.06 0.4960 WVFGRD96 6.0 160 65 10 3.96 0.4641 WVFGRD96 7.0 165 65 25 3.98 0.4590 WVFGRD96 8.0 160 70 20 3.98 0.4611 WVFGRD96 9.0 160 70 20 3.99 0.4568 WVFGRD96 10.0 165 70 20 4.00 0.4501 WVFGRD96 11.0 160 70 20 4.01 0.4434 WVFGRD96 12.0 165 65 20 4.03 0.4355 WVFGRD96 13.0 165 65 20 4.04 0.4266 WVFGRD96 14.0 165 65 25 4.05 0.4185 WVFGRD96 15.0 165 65 25 4.07 0.4049 WVFGRD96 16.0 165 65 25 4.08 0.3928 WVFGRD96 17.0 165 65 30 4.09 0.3811 WVFGRD96 18.0 165 65 30 4.10 0.3692 WVFGRD96 19.0 270 30 60 4.13 0.3631 WVFGRD96 20.0 270 35 60 4.14 0.3652 WVFGRD96 21.0 270 35 60 4.15 0.3675 WVFGRD96 22.0 265 40 55 4.16 0.3676 WVFGRD96 23.0 270 40 60 4.17 0.3679 WVFGRD96 24.0 270 40 60 4.18 0.3659 WVFGRD96 25.0 265 45 55 4.19 0.3606 WVFGRD96 26.0 265 45 55 4.20 0.3540 WVFGRD96 27.0 265 50 50 4.21 0.3466 WVFGRD96 28.0 265 50 50 4.22 0.3384 WVFGRD96 29.0 265 50 50 4.23 0.3297
The best solution is
WVFGRD96 2.0 120 30 -80 3.98 0.5279
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 Jul 13 09:17:23 CDT 2011