2009/04/13 08:41:08 42.271 13.505 9.9 3.00 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution ENS 2009/04/13 08:41:08:0 42.27 13.51 9.9 3.0 Italy Stations used: IV.CERT IV.CESX IV.CING IV.FDMO IV.FIAM IV.GIUL IV.LNSS IV.LPEL IV.MGAB IV.MIDA IV.MTCE IV.NRCA IV.POFI MN.AQU Filtering commands used: hp c 0.02 n 3 lp c 0.10 n 3 Best Fitting Double Couple Mo = 7.16e+20 dyne-cm Mw = 3.17 Z = 7 km Plane Strike Dip Rake NP1 170 65 -35 NP2 276 59 -150 Principal Axes: Axis Value Plunge Azimuth T 7.16e+20 4 224 N 0.00e+00 48 319 P -7.16e+20 42 131 Moment Tensor: (dyne-cm) Component Value Mxx 1.91e+20 Mxy 5.53e+20 Mxz 1.98e+20 Myy 1.23e+20 Myz -3.03e+20 Mzz -3.15e+20 ---########### ------################ --------#################### ---------##################### ----------######################## -----------######################### ------------########################## ------#######---------------############ --###########-------------------######## -#############----------------------###### ##############-------------------------### ###############--------------------------# ###############--------------------------- ###############------------------------- ###############------------- --------- ###############------------ P -------- ##############------------ ------- # ##########-------------------- T ###########----------------- ############--------------- ############---------- #########----- Global CMT Convention Moment Tensor: R T P -3.15e+20 1.98e+20 3.03e+20 1.98e+20 1.91e+20 -5.53e+20 3.03e+20 -5.53e+20 1.23e+20 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090413084108/index.html |
STK = 170 DIP = 65 RAKE = -35 MW = 3.17 HS = 7.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2009/04/13 08:41:08:0 42.27 13.51 9.9 3.0 Italy Stations used: IV.CERT IV.CESX IV.CING IV.FDMO IV.FIAM IV.GIUL IV.LNSS IV.LPEL IV.MGAB IV.MIDA IV.MTCE IV.NRCA IV.POFI MN.AQU Filtering commands used: hp c 0.02 n 3 lp c 0.10 n 3 Best Fitting Double Couple Mo = 7.16e+20 dyne-cm Mw = 3.17 Z = 7 km Plane Strike Dip Rake NP1 170 65 -35 NP2 276 59 -150 Principal Axes: Axis Value Plunge Azimuth T 7.16e+20 4 224 N 0.00e+00 48 319 P -7.16e+20 42 131 Moment Tensor: (dyne-cm) Component Value Mxx 1.91e+20 Mxy 5.53e+20 Mxz 1.98e+20 Myy 1.23e+20 Myz -3.03e+20 Mzz -3.15e+20 ---########### ------################ --------#################### ---------##################### ----------######################## -----------######################### ------------########################## ------#######---------------############ --###########-------------------######## -#############----------------------###### ##############-------------------------### ###############--------------------------# ###############--------------------------- ###############------------------------- ###############------------- --------- ###############------------ P -------- ##############------------ ------- # ##########-------------------- T ###########----------------- ############--------------- ############---------- #########----- Global CMT Convention Moment Tensor: R T P -3.15e+20 1.98e+20 3.03e+20 1.98e+20 1.91e+20 -5.53e+20 3.03e+20 -5.53e+20 1.23e+20 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090413084108/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 0.5 185 30 15 3.02 0.4132 WVFGRD96 1.0 190 35 30 2.99 0.4391 WVFGRD96 2.0 190 35 30 3.06 0.4956 WVFGRD96 3.0 185 85 -40 3.05 0.5220 WVFGRD96 4.0 175 70 -30 3.07 0.5621 WVFGRD96 5.0 170 65 -40 3.15 0.5761 WVFGRD96 6.0 170 65 -35 3.15 0.5951 WVFGRD96 7.0 170 65 -35 3.17 0.6010 WVFGRD96 8.0 175 70 -30 3.15 0.5959 WVFGRD96 9.0 175 70 -30 3.16 0.5859 WVFGRD96 10.0 175 70 -25 3.17 0.5747 WVFGRD96 11.0 175 70 -30 3.18 0.5596 WVFGRD96 12.0 175 70 -30 3.20 0.5453 WVFGRD96 13.0 170 65 -30 3.21 0.5286 WVFGRD96 14.0 170 65 -35 3.22 0.5123 WVFGRD96 15.0 170 65 -35 3.25 0.4998 WVFGRD96 16.0 165 60 -40 3.26 0.4835 WVFGRD96 17.0 165 60 -40 3.27 0.4679 WVFGRD96 18.0 165 60 -40 3.28 0.4528 WVFGRD96 19.0 165 60 -40 3.29 0.4380 WVFGRD96 20.0 165 60 -40 3.30 0.4239 WVFGRD96 21.0 165 60 -40 3.31 0.4098 WVFGRD96 22.0 165 60 -45 3.31 0.3971 WVFGRD96 23.0 160 55 -50 3.32 0.3848 WVFGRD96 24.0 160 55 -50 3.33 0.3736 WVFGRD96 25.0 160 55 -50 3.33 0.3618 WVFGRD96 26.0 160 55 -50 3.34 0.3516 WVFGRD96 27.0 175 70 -30 3.34 0.3416 WVFGRD96 28.0 180 80 -25 3.36 0.3390 WVFGRD96 29.0 180 80 -25 3.37 0.3380
The best solution is
WVFGRD96 7.0 170 65 -35 3.17 0.6010
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. The number in black at the rightr of each predicted traces 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 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. |
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 Apr 30 14:38:40 CDT 2009