2009/04/13 21:14:24 42.504 13.363 7.5 4.90 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/13 21:14:24:0 42.50 13.36 7.5 4.9 Italy
Stations used:
IV.ASSB IV.CAFR IV.CERT IV.CESI IV.CESX IV.CING IV.FAGN
IV.FDMO IV.FIAM IV.GUAR IV.INTR IV.LNSS IV.LPEL IV.MA9
IV.MNS IV.MTCE IV.OFFI IV.POFI IV.RDP IV.RMP IV.TERO
IV.TRTR IV.VVLD MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 2.72e+23 dyne-cm
Mw = 4.89
Z = 9 km
Plane Strike Dip Rake
NP1 155 55 -80
NP2 318 36 -104
Principal Axes:
Axis Value Plunge Azimuth
T 2.72e+23 9 238
N 0.00e+00 8 329
P -2.72e+23 77 99
Moment Tensor: (dyne-cm)
Component Value
Mxx 7.47e+22
Mxy 1.21e+23
Mxz -1.42e+22
Myy 1.77e+23
Myz -9.46e+22
Mzz -2.52e+23
##############
--####################
-###---------###############
####---------------###########
######-----------------###########
#######--------------------#########
########---------------------#########
#########-----------------------########
#########------------------------#######
###########------------------------#######
###########------------ ----------######
############----------- P ----------######
#############---------- -----------#####
############------------------------####
#############-----------------------####
# ##########---------------------###
T ###########--------------------##
############------------------##
##############----------------
################------------
################------
##############
Global CMT Convention Moment Tensor:
R T P
-2.52e+23 -1.42e+22 9.46e+22
-1.42e+22 7.47e+22 -1.21e+23
9.46e+22 -1.21e+23 1.77e+23
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090413211424/index.html
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STK = 155
DIP = 55
RAKE = -80
MW = 4.89
HS = 9.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/13 21:14:24:0 42.50 13.36 7.5 4.9 Italy
Stations used:
IV.ASSB IV.CAFR IV.CERT IV.CESI IV.CESX IV.CING IV.FAGN
IV.FDMO IV.FIAM IV.GUAR IV.INTR IV.LNSS IV.LPEL IV.MA9
IV.MNS IV.MTCE IV.OFFI IV.POFI IV.RDP IV.RMP IV.TERO
IV.TRTR IV.VVLD MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 2.72e+23 dyne-cm
Mw = 4.89
Z = 9 km
Plane Strike Dip Rake
NP1 155 55 -80
NP2 318 36 -104
Principal Axes:
Axis Value Plunge Azimuth
T 2.72e+23 9 238
N 0.00e+00 8 329
P -2.72e+23 77 99
Moment Tensor: (dyne-cm)
Component Value
Mxx 7.47e+22
Mxy 1.21e+23
Mxz -1.42e+22
Myy 1.77e+23
Myz -9.46e+22
Mzz -2.52e+23
##############
--####################
-###---------###############
####---------------###########
######-----------------###########
#######--------------------#########
########---------------------#########
#########-----------------------########
#########------------------------#######
###########------------------------#######
###########------------ ----------######
############----------- P ----------######
#############---------- -----------#####
############------------------------####
#############-----------------------####
# ##########---------------------###
T ###########--------------------##
############------------------##
##############----------------
################------------
################------
##############
Global CMT Convention Moment Tensor:
R T P
-2.52e+23 -1.42e+22 9.46e+22
-1.42e+22 7.47e+22 -1.21e+23
9.46e+22 -1.21e+23 1.77e+23
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090413211424/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 0.5 325 40 85 4.48 0.2445
WVFGRD96 1.0 0 55 -35 4.44 0.1961
WVFGRD96 2.0 350 40 -55 4.64 0.2663
WVFGRD96 3.0 0 35 -35 4.70 0.3260
WVFGRD96 4.0 350 30 -60 4.74 0.3748
WVFGRD96 5.0 345 30 -70 4.76 0.4105
WVFGRD96 6.0 345 30 -70 4.77 0.4260
WVFGRD96 7.0 320 35 -105 4.80 0.4344
WVFGRD96 8.0 320 35 -105 4.88 0.4609
WVFGRD96 9.0 155 55 -80 4.89 0.4628
WVFGRD96 10.0 155 55 -80 4.89 0.4568
WVFGRD96 11.0 150 55 -90 4.89 0.4447
WVFGRD96 12.0 165 60 -65 4.91 0.4310
WVFGRD96 13.0 160 60 -75 4.91 0.4167
WVFGRD96 14.0 10 65 10 4.91 0.4074
WVFGRD96 15.0 15 65 15 4.92 0.4003
WVFGRD96 16.0 10 65 5 4.93 0.3911
WVFGRD96 17.0 15 60 15 4.94 0.3827
WVFGRD96 18.0 15 60 10 4.95 0.3745
WVFGRD96 19.0 15 60 15 4.96 0.3662
WVFGRD96 20.0 15 60 15 4.97 0.3581
WVFGRD96 21.0 15 60 15 4.98 0.3485
WVFGRD96 22.0 15 60 15 4.98 0.3398
WVFGRD96 23.0 15 60 15 4.99 0.3312
WVFGRD96 24.0 15 60 15 5.00 0.3223
WVFGRD96 25.0 15 60 15 5.00 0.3135
WVFGRD96 26.0 15 60 15 5.00 0.3047
WVFGRD96 27.0 15 55 10 5.01 0.2959
WVFGRD96 28.0 15 55 10 5.01 0.2877
WVFGRD96 29.0 20 55 15 5.01 0.2801
The best solution is
WVFGRD96 9.0 155 55 -80 4.89 0.4628
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=Wed Apr 15 15:54:16 CDT 2009