2009/06/25 23:31:54 43.256 13.085 7.6 3.20 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution ENS 2009/06/25 23:31:54:0 43.26 13.09 7.6 3.2 Italy Stations used: IV.AOI IV.ARVD IV.ASQU IV.CESX IV.CING IV.CSNT IV.FDMO IV.GUMA IV.OFFI IV.PARC IV.PESA Filtering commands used: hp c 0.02 n 3 lp c 0.10 n 3 Best Fitting Double Couple Mo = 6.24e+20 dyne-cm Mw = 3.13 Z = 6 km Plane Strike Dip Rake NP1 175 55 -65 NP2 316 42 -121 Principal Axes: Axis Value Plunge Azimuth T 6.24e+20 7 247 N 0.00e+00 20 340 P -6.24e+20 69 140 Moment Tensor: (dyne-cm) Component Value Mxx 4.15e+19 Mxy 2.59e+20 Mxz 1.34e+20 Myy 4.90e+20 Myz -2.06e+20 Mzz -5.31e+20 ----########## ------################ ---#####-################### ########--------############## ##########-----------############# ##########---------------########### ###########-----------------########## ###########-------------------########## ###########---------------------######## ############----------------------######## ############-----------------------####### ############-----------------------####### ############----------- ----------###### ############---------- P ----------##### # ########---------- -----------#### T #########-----------------------### #########-----------------------## ###########---------------------## ##########-------------------- ##########------------------ #########------------- #######------- Global CMT Convention Moment Tensor: R T P -5.31e+20 1.34e+20 2.06e+20 1.34e+20 4.15e+19 -2.59e+20 2.06e+20 -2.59e+20 4.90e+20 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090625233154/index.html |
STK = 175 DIP = 55 RAKE = -65 MW = 3.13 HS = 6.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2009/06/25 23:31:54:0 43.26 13.09 7.6 3.2 Italy Stations used: IV.AOI IV.ARVD IV.ASQU IV.CESX IV.CING IV.CSNT IV.FDMO IV.GUMA IV.OFFI IV.PARC IV.PESA Filtering commands used: hp c 0.02 n 3 lp c 0.10 n 3 Best Fitting Double Couple Mo = 6.24e+20 dyne-cm Mw = 3.13 Z = 6 km Plane Strike Dip Rake NP1 175 55 -65 NP2 316 42 -121 Principal Axes: Axis Value Plunge Azimuth T 6.24e+20 7 247 N 0.00e+00 20 340 P -6.24e+20 69 140 Moment Tensor: (dyne-cm) Component Value Mxx 4.15e+19 Mxy 2.59e+20 Mxz 1.34e+20 Myy 4.90e+20 Myz -2.06e+20 Mzz -5.31e+20 ----########## ------################ ---#####-################### ########--------############## ##########-----------############# ##########---------------########### ###########-----------------########## ###########-------------------########## ###########---------------------######## ############----------------------######## ############-----------------------####### ############-----------------------####### ############----------- ----------###### ############---------- P ----------##### # ########---------- -----------#### T #########-----------------------### #########-----------------------## ###########---------------------## ##########-------------------- ##########------------------ #########------------- #######------- Global CMT Convention Moment Tensor: R T P -5.31e+20 1.34e+20 2.06e+20 1.34e+20 4.15e+19 -2.59e+20 2.06e+20 -2.59e+20 4.90e+20 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090625233154/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 0.5 170 65 -80 2.93 0.2174 WVFGRD96 1.0 170 60 -75 2.92 0.2176 WVFGRD96 2.0 175 60 -65 2.98 0.2395 WVFGRD96 3.0 185 75 -65 3.01 0.2551 WVFGRD96 4.0 175 55 -65 3.05 0.2764 WVFGRD96 5.0 175 55 -70 3.12 0.2865 WVFGRD96 6.0 175 55 -65 3.13 0.2962 WVFGRD96 7.0 175 55 -65 3.13 0.2918 WVFGRD96 8.0 180 60 -55 3.10 0.2766 WVFGRD96 9.0 195 90 -25 3.07 0.2641 WVFGRD96 10.0 210 60 25 3.09 0.2575 WVFGRD96 11.0 210 60 25 3.10 0.2564 WVFGRD96 12.0 210 60 25 3.12 0.2540 WVFGRD96 13.0 210 60 25 3.13 0.2508 WVFGRD96 14.0 215 60 25 3.14 0.2466 WVFGRD96 15.0 215 55 25 3.16 0.2384 WVFGRD96 16.0 215 55 25 3.17 0.2331 WVFGRD96 17.0 210 55 20 3.18 0.2276 WVFGRD96 18.0 325 55 25 3.15 0.2235 WVFGRD96 19.0 325 55 25 3.16 0.2208 WVFGRD96 20.0 325 55 25 3.17 0.2190 WVFGRD96 21.0 325 55 30 3.18 0.2178 WVFGRD96 22.0 325 50 30 3.20 0.2179 WVFGRD96 23.0 325 50 30 3.21 0.2184 WVFGRD96 24.0 325 50 35 3.22 0.2187 WVFGRD96 25.0 325 45 35 3.23 0.2188 WVFGRD96 26.0 325 45 40 3.25 0.2205 WVFGRD96 27.0 325 45 40 3.26 0.2214 WVFGRD96 28.0 330 45 45 3.27 0.2210 WVFGRD96 29.0 330 45 50 3.29 0.2214
The best solution is
WVFGRD96 6.0 175 55 -65 3.13 0.2962
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 Jun 25 21:29:58 CDT 2009