2009/04/15 22:53:07 42.505 13.312 8.6 3.80 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/15 22:53:07:0 42.51 13.31 8.6 3.8 Italy
Stations used:
IV.ASSB IV.CERT IV.CESX IV.CING IV.FAGN IV.FDMO IV.FIAM
IV.GUAR IV.INTR IV.LNSS IV.MNS IV.MTCE IV.NRCA IV.OFFI
IV.RMP IV.TERO IV.TRTR MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 8.32e+21 dyne-cm
Mw = 3.88
Z = 8 km
Plane Strike Dip Rake
NP1 160 50 -65
NP2 304 46 -117
Principal Axes:
Axis Value Plunge Azimuth
T 8.32e+21 2 233
N 0.00e+00 19 323
P -8.32e+21 71 137
Moment Tensor: (dyne-cm)
Component Value
Mxx 2.60e+21
Mxy 4.45e+21
Mxz 1.68e+21
Myy 4.82e+21
Myz -2.00e+21
Mzz -7.42e+21
##############
---###################
-----#######################
-----#########################
-#####------------################
#######---------------##############
########------------------############
#########--------------------###########
#########----------------------#########
##########------------------------########
##########-------------------------#######
###########----------- -----------######
###########----------- P ------------#####
###########---------- -------------###
############-------------------------###
############------------------------##
#########-----------------------#
T ##########----------------------
############------------------
#############---------------
#############---------
##############
Global CMT Convention Moment Tensor:
R T P
-7.42e+21 1.68e+21 2.00e+21
1.68e+21 2.60e+21 -4.45e+21
2.00e+21 -4.45e+21 4.82e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090415225307/index.html
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STK = 160
DIP = 50
RAKE = -65
MW = 3.88
HS = 8.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/15 22:53:07:0 42.51 13.31 8.6 3.8 Italy
Stations used:
IV.ASSB IV.CERT IV.CESX IV.CING IV.FAGN IV.FDMO IV.FIAM
IV.GUAR IV.INTR IV.LNSS IV.MNS IV.MTCE IV.NRCA IV.OFFI
IV.RMP IV.TERO IV.TRTR MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 8.32e+21 dyne-cm
Mw = 3.88
Z = 8 km
Plane Strike Dip Rake
NP1 160 50 -65
NP2 304 46 -117
Principal Axes:
Axis Value Plunge Azimuth
T 8.32e+21 2 233
N 0.00e+00 19 323
P -8.32e+21 71 137
Moment Tensor: (dyne-cm)
Component Value
Mxx 2.60e+21
Mxy 4.45e+21
Mxz 1.68e+21
Myy 4.82e+21
Myz -2.00e+21
Mzz -7.42e+21
##############
---###################
-----#######################
-----#########################
-#####------------################
#######---------------##############
########------------------############
#########--------------------###########
#########----------------------#########
##########------------------------########
##########-------------------------#######
###########----------- -----------######
###########----------- P ------------#####
###########---------- -------------###
############-------------------------###
############------------------------##
#########-----------------------#
T ##########----------------------
############------------------
#############---------------
#############---------
##############
Global CMT Convention Moment Tensor:
R T P
-7.42e+21 1.68e+21 2.00e+21
1.68e+21 2.60e+21 -4.45e+21
2.00e+21 -4.45e+21 4.82e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090415225307/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 -80 3.47 0.2213
WVFGRD96 1.0 350 50 -40 3.44 0.1883
WVFGRD96 2.0 345 50 -55 3.62 0.2476
WVFGRD96 3.0 345 30 -50 3.71 0.2991
WVFGRD96 4.0 340 35 -60 3.75 0.3573
WVFGRD96 5.0 335 40 -70 3.77 0.3936
WVFGRD96 6.0 160 50 -65 3.79 0.4128
WVFGRD96 7.0 165 50 -60 3.80 0.4197
WVFGRD96 8.0 160 50 -65 3.88 0.4392
WVFGRD96 9.0 160 50 -65 3.89 0.4323
WVFGRD96 10.0 160 50 -65 3.89 0.4174
WVFGRD96 11.0 170 55 -50 3.89 0.4022
WVFGRD96 12.0 170 55 -50 3.89 0.3889
WVFGRD96 13.0 175 60 -40 3.90 0.3740
WVFGRD96 14.0 175 60 -45 3.91 0.3610
WVFGRD96 15.0 175 65 -40 3.91 0.3488
WVFGRD96 16.0 185 80 -20 3.92 0.3388
WVFGRD96 17.0 185 90 -15 3.93 0.3328
WVFGRD96 18.0 185 90 -15 3.94 0.3244
WVFGRD96 19.0 185 90 -15 3.95 0.3168
WVFGRD96 20.0 20 60 20 3.94 0.3069
WVFGRD96 21.0 20 60 20 3.95 0.3022
WVFGRD96 22.0 20 60 20 3.96 0.2982
WVFGRD96 23.0 20 60 15 3.97 0.2942
WVFGRD96 24.0 20 60 15 3.98 0.2908
WVFGRD96 25.0 20 60 15 3.98 0.2867
WVFGRD96 26.0 20 55 15 3.99 0.2825
WVFGRD96 27.0 20 55 15 4.00 0.2788
WVFGRD96 28.0 20 55 15 4.00 0.2744
WVFGRD96 29.0 20 55 15 4.01 0.2699
The best solution is
WVFGRD96 8.0 160 50 -65 3.88 0.4392
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 14:23:17 CDT 2009