2009/04/08 22:56:50 42.5070 13.3640 10.2 4.30 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/08 22:56:50:0 42.51 13.36 10.2 4.3 Italy
Stations used:
IV.ARVD IV.ASSB IV.CERT IV.CESI IV.CESX IV.CING IV.FAGN
IV.FDMO IV.FIAM IV.GUAR IV.INTR IV.LATE IV.LNSS IV.MA9
IV.MGAB IV.MIDA IV.MNS IV.MTCE IV.MURB IV.NRCA IV.PIEI
IV.RDP IV.SACS IV.TERO IV.TOLF IV.TRTR
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 7.76e+21 dyne-cm
Mw = 3.86
Z = 8 km
Plane Strike Dip Rake
NP1 297 71 -107
NP2 160 25 -50
Principal Axes:
Axis Value Plunge Azimuth
T 7.76e+21 24 40
N 0.00e+00 16 303
P -7.76e+21 60 183
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.89e+21
Mxy 3.08e+21
Mxz 5.56e+21
Myy 2.67e+21
Myz 2.05e+21
Mzz -4.56e+21
##############
-#####################
---#########################
--###################### ###
---####################### T #####
---######################## ######
####-------###########################
####-------------#######################
####------------------##################
#####---------------------################
#####------------------------#############
#####---------------------------##########
#####-----------------------------########
#####------------------------------#####
######------------ ---------------####
#####------------ P -----------------#
######---------- -----------------
######----------------------------
######------------------------
#######---------------------
#######---------------
#########-----
Global CMT Convention Moment Tensor:
R T P
-4.56e+21 5.56e+21 -2.05e+21
5.56e+21 1.89e+21 -3.08e+21
-2.05e+21 -3.08e+21 2.67e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090408225650/index.html
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STK = 160
DIP = 25
RAKE = -50
MW = 3.86
HS = 8.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/08 22:56:50:0 42.51 13.36 10.2 4.3 Italy
Stations used:
IV.ARVD IV.ASSB IV.CERT IV.CESI IV.CESX IV.CING IV.FAGN
IV.FDMO IV.FIAM IV.GUAR IV.INTR IV.LATE IV.LNSS IV.MA9
IV.MGAB IV.MIDA IV.MNS IV.MTCE IV.MURB IV.NRCA IV.PIEI
IV.RDP IV.SACS IV.TERO IV.TOLF IV.TRTR
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 7.76e+21 dyne-cm
Mw = 3.86
Z = 8 km
Plane Strike Dip Rake
NP1 297 71 -107
NP2 160 25 -50
Principal Axes:
Axis Value Plunge Azimuth
T 7.76e+21 24 40
N 0.00e+00 16 303
P -7.76e+21 60 183
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.89e+21
Mxy 3.08e+21
Mxz 5.56e+21
Myy 2.67e+21
Myz 2.05e+21
Mzz -4.56e+21
##############
-#####################
---#########################
--###################### ###
---####################### T #####
---######################## ######
####-------###########################
####-------------#######################
####------------------##################
#####---------------------################
#####------------------------#############
#####---------------------------##########
#####-----------------------------########
#####------------------------------#####
######------------ ---------------####
#####------------ P -----------------#
######---------- -----------------
######----------------------------
######------------------------
#######---------------------
#######---------------
#########-----
Global CMT Convention Moment Tensor:
R T P
-4.56e+21 5.56e+21 -2.05e+21
5.56e+21 1.89e+21 -3.08e+21
-2.05e+21 -3.08e+21 2.67e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090408225650/index.html
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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 0.5 130 45 -90 3.51 0.3353
WVFGRD96 1.0 175 70 -20 3.45 0.2493
WVFGRD96 2.0 325 45 -70 3.67 0.3199
WVFGRD96 3.0 170 25 -30 3.72 0.3354
WVFGRD96 4.0 170 20 -35 3.74 0.4062
WVFGRD96 5.0 160 20 -50 3.76 0.4540
WVFGRD96 6.0 170 25 -40 3.77 0.4840
WVFGRD96 7.0 170 25 -40 3.77 0.5001
WVFGRD96 8.0 160 25 -50 3.86 0.5144
WVFGRD96 9.0 165 30 -50 3.87 0.5097
WVFGRD96 10.0 165 30 -50 3.87 0.4989
WVFGRD96 11.0 170 30 -45 3.88 0.4862
WVFGRD96 12.0 170 30 -45 3.88 0.4709
WVFGRD96 13.0 340 70 -50 3.91 0.4590
WVFGRD96 14.0 340 70 -50 3.92 0.4499
WVFGRD96 15.0 345 70 -40 3.94 0.4414
WVFGRD96 16.0 345 70 -40 3.95 0.4335
WVFGRD96 17.0 345 70 -40 3.96 0.4248
WVFGRD96 18.0 345 70 -40 3.97 0.4151
WVFGRD96 19.0 345 70 -40 3.98 0.4048
WVFGRD96 20.0 345 70 -40 3.99 0.3931
WVFGRD96 21.0 345 70 -40 4.00 0.3827
WVFGRD96 22.0 345 70 -40 4.01 0.3697
WVFGRD96 23.0 345 70 -40 4.01 0.3569
WVFGRD96 24.0 345 70 -40 4.02 0.3437
WVFGRD96 25.0 345 70 -40 4.02 0.3304
WVFGRD96 26.0 350 75 -40 4.03 0.3181
WVFGRD96 27.0 350 75 -40 4.03 0.3058
WVFGRD96 28.0 350 75 -40 4.03 0.2927
WVFGRD96 29.0 160 80 60 4.02 0.2836
The best solution is
WVFGRD96 8.0 160 25 -50 3.86 0.5144
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 WUS used for the waveform synthetic seismograms and for the surface wave eigenfunctions and dispersion is as follows:
MODEL.01
Model after 8 iterations
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
1.9000 3.4065 2.0089 2.2150 0.302E-02 0.679E-02 0.00 0.00 1.00 1.00
6.1000 5.5445 3.2953 2.6089 0.349E-02 0.784E-02 0.00 0.00 1.00 1.00
13.0000 6.2708 3.7396 2.7812 0.212E-02 0.476E-02 0.00 0.00 1.00 1.00
19.0000 6.4075 3.7680 2.8223 0.111E-02 0.249E-02 0.00 0.00 1.00 1.00
0.0000 7.9000 4.6200 3.2760 0.164E-10 0.370E-10 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 16 12:23:40 CDT 2009