2015/09/18 19:24:52 43.63 12.32 9.0 3.5 Italy
USGS Felt map for this earthquake
SLU Moment Tensor Solution ENS 2015/09/18 19:24:52:0 43.63 12.32 9.0 3.5 Italy Stations used: GU.MAIM IV.ARCI IV.ARVD IV.ASQU IV.ATFO IV.ATTE IV.ATVO IV.BDI IV.CAFI IV.CASP IV.CESI IV.CESX IV.CING IV.CRE IV.CSNT IV.FIAM IV.FSSB IV.GROG IV.GUMA IV.LAV9 IV.MGAB IV.MTCE IV.MURB IV.NRCA IV.OSSC IV.PESA IV.POFI IV.PTQR IV.RMP IV.SACS IV.SAMA IV.SNTG IV.TERO MN.AQU MN.VLC Filtering commands used: cut o DIST/3.3 -20 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.07 n 3 Best Fitting Double Couple Mo = 2.85e+21 dyne-cm Mw = 3.57 Z = 3 km Plane Strike Dip Rake NP1 311 55 -87 NP2 125 35 -95 Principal Axes: Axis Value Plunge Azimuth T 2.85e+21 10 39 N 0.00e+00 3 129 P -2.85e+21 80 235 Moment Tensor: (dyne-cm) Component Value Mxx 1.66e+21 Mxy 1.30e+21 Mxz 6.79e+20 Myy 1.01e+21 Myz 7.24e+20 Mzz -2.67e+21 ############## ###################### ######################### #-----#################### T # --------------############## ### #------------------################# #----------------------############### ##------------------------############## ##--------------------------############ ####---------------------------########### ####-------------- -----------########## #####------------- P ------------######### ######------------ -------------######## ######----------------------------###### #######----------------------------##### ########--------------------------#### #########-------------------------## ###########----------------------# ############-----------------# ############################ ###################### ############## Global CMT Convention Moment Tensor: R T P -2.67e+21 6.79e+20 -7.24e+20 6.79e+20 1.66e+21 -1.30e+21 -7.24e+20 -1.30e+21 1.01e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20150918192452/index.html |
STK = 125 DIP = 35 RAKE = -95 MW = 3.57 HS = 3.0
The NDK file is 20150918192452.ndk The waveform inversion is preferred.
The following compares this source inversion to others
SLU Moment Tensor Solution ENS 2015/09/18 19:24:52:0 43.63 12.32 9.0 3.5 Italy Stations used: GU.MAIM IV.ARCI IV.ARVD IV.ASQU IV.ATFO IV.ATTE IV.ATVO IV.BDI IV.CAFI IV.CASP IV.CESI IV.CESX IV.CING IV.CRE IV.CSNT IV.FIAM IV.FSSB IV.GROG IV.GUMA IV.LAV9 IV.MGAB IV.MTCE IV.MURB IV.NRCA IV.OSSC IV.PESA IV.POFI IV.PTQR IV.RMP IV.SACS IV.SAMA IV.SNTG IV.TERO MN.AQU MN.VLC Filtering commands used: cut o DIST/3.3 -20 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.07 n 3 Best Fitting Double Couple Mo = 2.85e+21 dyne-cm Mw = 3.57 Z = 3 km Plane Strike Dip Rake NP1 311 55 -87 NP2 125 35 -95 Principal Axes: Axis Value Plunge Azimuth T 2.85e+21 10 39 N 0.00e+00 3 129 P -2.85e+21 80 235 Moment Tensor: (dyne-cm) Component Value Mxx 1.66e+21 Mxy 1.30e+21 Mxz 6.79e+20 Myy 1.01e+21 Myz 7.24e+20 Mzz -2.67e+21 ############## ###################### ######################### #-----#################### T # --------------############## ### #------------------################# #----------------------############### ##------------------------############## ##--------------------------############ ####---------------------------########### ####-------------- -----------########## #####------------- P ------------######### ######------------ -------------######## ######----------------------------###### #######----------------------------##### ########--------------------------#### #########-------------------------## ###########----------------------# ############-----------------# ############################ ###################### ############## Global CMT Convention Moment Tensor: R T P -2.67e+21 6.79e+20 -7.24e+20 6.79e+20 1.66e+21 -1.30e+21 -7.24e+20 -1.30e+21 1.01e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20150918192452/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:
cut o DIST/3.3 -20 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.07 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 55 -70 3.44 0.5602 WVFGRD96 2.0 320 60 -80 3.53 0.6201 WVFGRD96 3.0 125 35 -95 3.57 0.6403 WVFGRD96 4.0 125 40 -95 3.59 0.5995 WVFGRD96 5.0 125 35 -95 3.64 0.6154 WVFGRD96 6.0 125 35 -95 3.61 0.5013 WVFGRD96 7.0 180 65 20 3.50 0.4632 WVFGRD96 8.0 180 65 20 3.50 0.4669 WVFGRD96 9.0 180 65 25 3.50 0.4631 WVFGRD96 10.0 180 65 25 3.51 0.4602 WVFGRD96 11.0 180 65 25 3.52 0.4590 WVFGRD96 12.0 180 65 25 3.52 0.4584 WVFGRD96 13.0 185 60 25 3.53 0.4592 WVFGRD96 14.0 185 60 25 3.54 0.4609 WVFGRD96 15.0 185 60 30 3.56 0.4548 WVFGRD96 16.0 185 60 30 3.57 0.4535 WVFGRD96 17.0 185 60 30 3.58 0.4521 WVFGRD96 18.0 185 60 30 3.58 0.4500 WVFGRD96 19.0 185 60 30 3.59 0.4473 WVFGRD96 20.0 185 60 30 3.60 0.4439 WVFGRD96 21.0 185 60 30 3.60 0.4399 WVFGRD96 22.0 185 60 30 3.61 0.4351 WVFGRD96 23.0 190 55 40 3.62 0.4309 WVFGRD96 24.0 190 55 40 3.63 0.4263 WVFGRD96 25.0 190 55 40 3.63 0.4215 WVFGRD96 26.0 185 65 25 3.65 0.4174 WVFGRD96 27.0 185 65 25 3.66 0.4139 WVFGRD96 28.0 305 50 85 3.70 0.4120 WVFGRD96 29.0 135 40 100 3.72 0.4130
The best solution is
WVFGRD96 3.0 125 35 -95 3.57 0.6403
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
cut o DIST/3.3 -20 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.07 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=Mon Sep 21 10:00:18 CDT 2015