2009/05/09 09:09:40 42.350 13.359 10.50 3.20 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution ENS 2009/05/09 09:09:40:0 42.35 13.36 10.5 3.2 Italy Stations used: IV.ARVD IV.CAMP IV.CERT IV.CESX IV.CING IV.FAGN IV.FDMO IV.FIAM IV.GUAR IV.GUMA IV.MNS IV.MTCE IV.NRCA IV.OFFI IV.PIEI IV.POFI IV.RMP IV.TERO IV.VVLD Filtering commands used: hp c 0.02 n 3 lp c 0.10 n 3 Best Fitting Double Couple Mo = 1.43e+21 dyne-cm Mw = 3.37 Z = 9 km Plane Strike Dip Rake NP1 136 57 -103 NP2 340 35 -70 Principal Axes: Axis Value Plunge Azimuth T 1.43e+21 11 236 N 0.00e+00 11 143 P -1.43e+21 74 10 Moment Tensor: (dyne-cm) Component Value Mxx 3.28e+20 Mxy 6.20e+20 Mxz -5.33e+20 Myy 9.34e+20 Myz -2.95e+20 Mzz -1.26e+21 --############ ------------########## ------------------########## ----------------------######## ##-----------------------######### ####------------------------######## #####-------------------------######## ######--------------------------######## #######------------ -----------####### #########----------- P -----------######## ##########---------- ------------####### ###########------------------------####### #############----------------------####### #############---------------------###### ###############-------------------###### ## ###########-----------------##### # T #############--------------##### ################-----------#### #####################------### #########################--- ####################-- ############## Global CMT Convention Moment Tensor: R T P -1.26e+21 -5.33e+20 2.95e+20 -5.33e+20 3.28e+20 -6.20e+20 2.95e+20 -6.20e+20 9.34e+20 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090509090940/index.html |
STK = 340 DIP = 35 RAKE = -70 MW = 3.37 HS = 9.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2009/05/09 09:09:40:0 42.35 13.36 10.5 3.2 Italy Stations used: IV.ARVD IV.CAMP IV.CERT IV.CESX IV.CING IV.FAGN IV.FDMO IV.FIAM IV.GUAR IV.GUMA IV.MNS IV.MTCE IV.NRCA IV.OFFI IV.PIEI IV.POFI IV.RMP IV.TERO IV.VVLD Filtering commands used: hp c 0.02 n 3 lp c 0.10 n 3 Best Fitting Double Couple Mo = 1.43e+21 dyne-cm Mw = 3.37 Z = 9 km Plane Strike Dip Rake NP1 136 57 -103 NP2 340 35 -70 Principal Axes: Axis Value Plunge Azimuth T 1.43e+21 11 236 N 0.00e+00 11 143 P -1.43e+21 74 10 Moment Tensor: (dyne-cm) Component Value Mxx 3.28e+20 Mxy 6.20e+20 Mxz -5.33e+20 Myy 9.34e+20 Myz -2.95e+20 Mzz -1.26e+21 --############ ------------########## ------------------########## ----------------------######## ##-----------------------######### ####------------------------######## #####-------------------------######## ######--------------------------######## #######------------ -----------####### #########----------- P -----------######## ##########---------- ------------####### ###########------------------------####### #############----------------------####### #############---------------------###### ###############-------------------###### ## ###########-----------------##### # T #############--------------##### ################-----------#### #####################------### #########################--- ####################-- ############## Global CMT Convention Moment Tensor: R T P -1.26e+21 -5.33e+20 2.95e+20 -5.33e+20 3.28e+20 -6.20e+20 2.95e+20 -6.20e+20 9.34e+20 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090509090940/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 0.5 110 55 90 3.08 0.2850 WVFGRD96 1.0 275 30 70 3.13 0.2530 WVFGRD96 2.0 245 25 45 3.21 0.2602 WVFGRD96 3.0 25 20 -10 3.23 0.3246 WVFGRD96 4.0 15 25 -25 3.23 0.3756 WVFGRD96 5.0 0 25 -40 3.34 0.4178 WVFGRD96 6.0 350 30 -55 3.37 0.4686 WVFGRD96 7.0 345 30 -60 3.38 0.5059 WVFGRD96 8.0 340 35 -70 3.37 0.5248 WVFGRD96 9.0 340 35 -70 3.37 0.5286 WVFGRD96 10.0 340 35 -70 3.38 0.5229 WVFGRD96 11.0 345 40 -60 3.38 0.5111 WVFGRD96 12.0 345 40 -60 3.39 0.4951 WVFGRD96 13.0 350 40 -55 3.39 0.4752 WVFGRD96 14.0 355 35 -50 3.39 0.4575 WVFGRD96 15.0 0 30 -40 3.42 0.4451 WVFGRD96 16.0 5 30 -35 3.43 0.4294 WVFGRD96 17.0 10 30 -25 3.43 0.4141 WVFGRD96 18.0 10 35 -25 3.44 0.3990 WVFGRD96 19.0 10 35 -25 3.45 0.3833 WVFGRD96 20.0 30 30 -10 3.45 0.3695 WVFGRD96 21.0 40 30 5 3.45 0.3582 WVFGRD96 22.0 50 25 15 3.46 0.3503 WVFGRD96 23.0 55 25 20 3.46 0.3452 WVFGRD96 24.0 60 25 25 3.47 0.3413 WVFGRD96 25.0 65 25 30 3.48 0.3384 WVFGRD96 26.0 65 25 30 3.48 0.3345 WVFGRD96 27.0 70 25 35 3.49 0.3304 WVFGRD96 28.0 65 25 30 3.49 0.3258 WVFGRD96 29.0 65 25 30 3.49 0.3247
The best solution is
WVFGRD96 9.0 340 35 -70 3.37 0.5286
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=Sun Aug 23 12:31:39 CDT 2009