2014/06/04 21:20:41 39.876 16.001 8.9 3.70 Italy
USGS Felt map for this earthquake
SLU Moment Tensor Solution ENS 2014/06/04 21:20:41:0 39.88 16.00 8.9 3.7 Italy Stations used: IV.AMUR IV.BULG IV.CAR1 IV.CDRU IV.CELI IV.CMPR IV.ILLI IV.JOPP IV.MCEL IV.MCRV IV.MCSR IV.MGR IV.MIGL IV.MODR IV.MPNC IV.MRLC IV.MSRU IV.MTSN IV.MUCR IV.NOCI IV.NOV IV.ORI IV.PIGN IV.PIPA IV.PLAC IV.SALB IV.SERS IV.SIRI IV.SLCN IV.VAGA MN.CEL MN.TIP Filtering commands used: cut a -10 a 60 rtr taper w 0.1 hp c 0.02 n 3 lp c 0.10 n 3 Best Fitting Double Couple Mo = 4.62e+21 dyne-cm Mw = 3.71 Z = 6 km Plane Strike Dip Rake NP1 170 55 -85 NP2 341 35 -97 Principal Axes: Axis Value Plunge Azimuth T 4.62e+21 10 256 N 0.00e+00 4 347 P -4.62e+21 79 99 Moment Tensor: (dyne-cm) Component Value Mxx 2.43e+20 Mxy 1.05e+21 Mxz -4.59e+19 Myy 4.09e+21 Myz -1.59e+21 Mzz -4.33e+21 ##-########### #####--------######### #######------------######### #######---------------######## #########-----------------######## #########-------------------######## ##########--------------------######## ###########---------------------######## ###########----------------------####### ############----------------------######## ############----------- ---------####### ############----------- P ---------####### # #########---------- ---------####### T #########----------------------###### ##########---------------------###### ############---------------------##### ############-------------------##### ############-----------------##### ###########----------------### ############------------#### ##########----------## #########----- Global CMT Convention Moment Tensor: R T P -4.33e+21 -4.59e+19 1.59e+21 -4.59e+19 2.43e+20 -1.05e+21 1.59e+21 -1.05e+21 4.09e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20140604212041/index.html |
STK = 170 DIP = 55 RAKE = -85 MW = 3.71 HS = 6.0
The NDK file is 20140604212041.ndk The waveform inversion is preferred.
The following compares this source inversion to others
SLU Moment Tensor Solution ENS 2014/06/04 21:20:41:0 39.88 16.00 8.9 3.7 Italy Stations used: IV.AMUR IV.BULG IV.CAR1 IV.CDRU IV.CELI IV.CMPR IV.ILLI IV.JOPP IV.MCEL IV.MCRV IV.MCSR IV.MGR IV.MIGL IV.MODR IV.MPNC IV.MRLC IV.MSRU IV.MTSN IV.MUCR IV.NOCI IV.NOV IV.ORI IV.PIGN IV.PIPA IV.PLAC IV.SALB IV.SERS IV.SIRI IV.SLCN IV.VAGA MN.CEL MN.TIP Filtering commands used: cut a -10 a 60 rtr taper w 0.1 hp c 0.02 n 3 lp c 0.10 n 3 Best Fitting Double Couple Mo = 4.62e+21 dyne-cm Mw = 3.71 Z = 6 km Plane Strike Dip Rake NP1 170 55 -85 NP2 341 35 -97 Principal Axes: Axis Value Plunge Azimuth T 4.62e+21 10 256 N 0.00e+00 4 347 P -4.62e+21 79 99 Moment Tensor: (dyne-cm) Component Value Mxx 2.43e+20 Mxy 1.05e+21 Mxz -4.59e+19 Myy 4.09e+21 Myz -1.59e+21 Mzz -4.33e+21 ##-########### #####--------######### #######------------######### #######---------------######## #########-----------------######## #########-------------------######## ##########--------------------######## ###########---------------------######## ###########----------------------####### ############----------------------######## ############----------- ---------####### ############----------- P ---------####### # #########---------- ---------####### T #########----------------------###### ##########---------------------###### ############---------------------##### ############-------------------##### ############-----------------##### ###########----------------### ############------------#### ##########----------## #########----- Global CMT Convention Moment Tensor: R T P -4.33e+21 -4.59e+19 1.59e+21 -4.59e+19 2.43e+20 -1.05e+21 1.59e+21 -1.05e+21 4.09e+21 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20140604212041/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 a -10 a 60 rtr taper w 0.1 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 1.0 180 50 -80 3.44 0.2885 WVFGRD96 2.0 185 70 -70 3.56 0.3333 WVFGRD96 3.0 185 65 -65 3.56 0.3823 WVFGRD96 4.0 175 60 -75 3.59 0.4294 WVFGRD96 5.0 175 60 -75 3.69 0.4863 WVFGRD96 6.0 170 55 -85 3.71 0.5101 WVFGRD96 7.0 170 55 -85 3.70 0.5058 WVFGRD96 8.0 30 65 25 3.63 0.4752 WVFGRD96 9.0 30 65 20 3.64 0.4810 WVFGRD96 10.0 30 65 20 3.65 0.4803 WVFGRD96 11.0 30 70 20 3.66 0.4744 WVFGRD96 12.0 30 70 20 3.67 0.4657 WVFGRD96 13.0 30 70 20 3.67 0.4555 WVFGRD96 14.0 30 70 20 3.68 0.4440 WVFGRD96 15.0 30 70 25 3.70 0.4285 WVFGRD96 16.0 30 70 25 3.70 0.4157 WVFGRD96 17.0 30 70 25 3.71 0.4018 WVFGRD96 18.0 30 70 25 3.71 0.3877 WVFGRD96 19.0 30 70 25 3.71 0.3743 WVFGRD96 20.0 30 65 25 3.72 0.3616 WVFGRD96 21.0 30 65 25 3.73 0.3507 WVFGRD96 22.0 30 60 20 3.74 0.3419 WVFGRD96 23.0 30 60 20 3.75 0.3348 WVFGRD96 24.0 30 60 20 3.75 0.3279 WVFGRD96 25.0 35 55 25 3.76 0.3221 WVFGRD96 26.0 35 55 25 3.76 0.3162 WVFGRD96 27.0 35 55 20 3.78 0.3119 WVFGRD96 28.0 35 60 25 3.79 0.3085 WVFGRD96 29.0 35 60 25 3.81 0.3073
The best solution is
WVFGRD96 6.0 170 55 -85 3.71 0.5101
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 a -10 a 60 rtr taper w 0.1 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 Jun 4 18:26:11 CDT 2014