2009/04/09 00:52:59 42.484 13.343 15.4 5.10 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/09 00:52:59:0 42.48 13.34 15.4 5.1 Italy
Stations used:
IV.AOI IV.ARVD IV.ASSB IV.CAFI IV.CAFR IV.CERA IV.CERT
IV.CESI IV.CESX IV.CING IV.FDMO IV.FRES IV.FSSB IV.GIUL
IV.GUAR IV.INTR IV.MA9 IV.MGAB IV.MIDA IV.MNS IV.MTCE
IV.MURB IV.PIEI IV.POFI IV.RDP IV.RNI2 IV.SACS IV.TOLF
IV.VAGA MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 8.81e+23 dyne-cm
Mw = 5.23
Z = 8 km
Plane Strike Dip Rake
NP1 319 65 -95
NP2 150 25 -80
Principal Axes:
Axis Value Plunge Azimuth
T 8.81e+23 20 52
N 0.00e+00 4 321
P -8.81e+23 69 220
Moment Tensor: (dyne-cm)
Component Value
Mxx 2.22e+23
Mxy 3.20e+23
Mxz 3.99e+23
Myy 4.43e+23
Myz 4.14e+23
Mzz -6.65e+23
##############
######################
--##########################
#------#######################
##-----------################ ##
###-------------############## T ###
###-----------------########### ####
####-------------------#################
###---------------------################
####-----------------------###############
####------------------------##############
#####-------------------------############
#####----------- ------------###########
#####---------- P -------------#########
######--------- --------------########
######-------------------------#######
######-------------------------#####
######------------------------####
######-----------------------#
########--------------------
#########-------------
##############
Global CMT Convention Moment Tensor:
R T P
-6.65e+23 3.99e+23 -4.14e+23
3.99e+23 2.22e+23 -3.20e+23
-4.14e+23 -3.20e+23 4.43e+23
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090409005259/index.html
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STK = 150
DIP = 25
RAKE = -80
MW = 5.23
HS = 8.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/09 00:52:59:0 42.48 13.34 15.4 5.1 Italy
Stations used:
IV.AOI IV.ARVD IV.ASSB IV.CAFI IV.CAFR IV.CERA IV.CERT
IV.CESI IV.CESX IV.CING IV.FDMO IV.FRES IV.FSSB IV.GIUL
IV.GUAR IV.INTR IV.MA9 IV.MGAB IV.MIDA IV.MNS IV.MTCE
IV.MURB IV.PIEI IV.POFI IV.RDP IV.RNI2 IV.SACS IV.TOLF
IV.VAGA MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 8.81e+23 dyne-cm
Mw = 5.23
Z = 8 km
Plane Strike Dip Rake
NP1 319 65 -95
NP2 150 25 -80
Principal Axes:
Axis Value Plunge Azimuth
T 8.81e+23 20 52
N 0.00e+00 4 321
P -8.81e+23 69 220
Moment Tensor: (dyne-cm)
Component Value
Mxx 2.22e+23
Mxy 3.20e+23
Mxz 3.99e+23
Myy 4.43e+23
Myz 4.14e+23
Mzz -6.65e+23
##############
######################
--##########################
#------#######################
##-----------################ ##
###-------------############## T ###
###-----------------########### ####
####-------------------#################
###---------------------################
####-----------------------###############
####------------------------##############
#####-------------------------############
#####----------- ------------###########
#####---------- P -------------#########
######--------- --------------########
######-------------------------#######
######-------------------------#####
######------------------------####
######-----------------------#
########--------------------
#########-------------
##############
Global CMT Convention Moment Tensor:
R T P
-6.65e+23 3.99e+23 -4.14e+23
3.99e+23 2.22e+23 -3.20e+23
-4.14e+23 -3.20e+23 4.43e+23
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090409005259/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 0.5 135 40 -95 4.87 0.2725
WVFGRD96 1.0 350 60 -45 4.80 0.1959
WVFGRD96 2.0 140 40 -90 5.02 0.2620
WVFGRD96 3.0 165 25 -55 5.07 0.2885
WVFGRD96 4.0 160 20 -65 5.10 0.3550
WVFGRD96 5.0 160 25 -65 5.12 0.3991
WVFGRD96 6.0 160 25 -65 5.13 0.4250
WVFGRD96 7.0 155 25 -75 5.14 0.4385
WVFGRD96 8.0 150 25 -80 5.23 0.4614
WVFGRD96 9.0 155 25 -75 5.24 0.4568
WVFGRD96 10.0 335 65 -75 5.25 0.4514
WVFGRD96 11.0 335 65 -75 5.25 0.4403
WVFGRD96 12.0 340 65 -65 5.25 0.4268
WVFGRD96 13.0 345 70 -55 5.26 0.4142
WVFGRD96 14.0 350 70 -45 5.26 0.4046
WVFGRD96 15.0 -5 75 -35 5.28 0.3963
WVFGRD96 16.0 -5 70 -35 5.28 0.3881
WVFGRD96 17.0 -5 70 -35 5.29 0.3795
WVFGRD96 18.0 -5 70 -35 5.30 0.3697
WVFGRD96 19.0 -5 70 -35 5.31 0.3600
WVFGRD96 20.0 0 70 -30 5.32 0.3504
WVFGRD96 21.0 0 70 -30 5.33 0.3428
WVFGRD96 22.0 0 70 -35 5.34 0.3333
WVFGRD96 23.0 0 70 -35 5.35 0.3243
WVFGRD96 24.0 0 70 -35 5.35 0.3154
WVFGRD96 25.0 -5 65 -40 5.36 0.3066
WVFGRD96 26.0 -5 65 -40 5.36 0.2978
WVFGRD96 27.0 -5 65 -40 5.37 0.2887
WVFGRD96 28.0 -5 65 -45 5.37 0.2799
WVFGRD96 29.0 -5 65 -45 5.38 0.2722
The best solution is
WVFGRD96 8.0 150 25 -80 5.23 0.4614
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 20:32:22 CDT 2009