2009/09/21 22:01:27 42.739 12.491 2.0 3.2 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/09/21 22:01:27:0 42.74 12.49 2.0 3.2 Italy
Stations used:
IV.ARCI IV.CESX IV.CING IV.FDMO IV.GUMA IV.MNS IV.MTCE
IV.MURB IV.OFFI IV.PARC IV.PIEI IV.SACS
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 5.25e+20 dyne-cm
Mw = 3.08
Z = 2 km
Plane Strike Dip Rake
NP1 318 45 -95
NP2 145 45 -85
Principal Axes:
Axis Value Plunge Azimuth
T 5.25e+20 0 51
N 0.00e+00 4 321
P -5.25e+20 86 143
Moment Tensor: (dyne-cm)
Component Value
Mxx 2.02e+20
Mxy 2.57e+20
Mxz 2.65e+19
Myy 3.20e+20
Myz -1.86e+19
Mzz -5.23e+20
##############
######################
--------####################
##-------------###############
###-----------------############ T
####--------------------#########
#####----------------------###########
######-----------------------###########
######-------------------------#########
########-------------------------#########
########------------ -----------########
#########----------- P ------------#######
##########---------- ------------#######
##########-------------------------#####
###########------------------------#####
###########-----------------------####
############---------------------###
#############-------------------##
##############---------------#
################------------
######################
##############
Global CMT Convention Moment Tensor:
R T P
-5.23e+20 2.65e+19 1.86e+19
2.65e+19 2.02e+20 -2.57e+20
1.86e+19 -2.57e+20 3.20e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090921220127/index.html
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STK = 145
DIP = 45
RAKE = -85
MW = 3.08
HS = 2.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/09/21 22:01:27:0 42.74 12.49 2.0 3.2 Italy
Stations used:
IV.ARCI IV.CESX IV.CING IV.FDMO IV.GUMA IV.MNS IV.MTCE
IV.MURB IV.OFFI IV.PARC IV.PIEI IV.SACS
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 5.25e+20 dyne-cm
Mw = 3.08
Z = 2 km
Plane Strike Dip Rake
NP1 318 45 -95
NP2 145 45 -85
Principal Axes:
Axis Value Plunge Azimuth
T 5.25e+20 0 51
N 0.00e+00 4 321
P -5.25e+20 86 143
Moment Tensor: (dyne-cm)
Component Value
Mxx 2.02e+20
Mxy 2.57e+20
Mxz 2.65e+19
Myy 3.20e+20
Myz -1.86e+19
Mzz -5.23e+20
##############
######################
--------####################
##-------------###############
###-----------------############ T
####--------------------#########
#####----------------------###########
######-----------------------###########
######-------------------------#########
########-------------------------#########
########------------ -----------########
#########----------- P ------------#######
##########---------- ------------#######
##########-------------------------#####
###########------------------------#####
###########-----------------------####
############---------------------###
#############-------------------##
##############---------------#
################------------
######################
##############
Global CMT Convention Moment Tensor:
R T P
-5.23e+20 2.65e+19 1.86e+19
2.65e+19 2.02e+20 -2.57e+20
1.86e+19 -2.57e+20 3.20e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090921220127/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 1.0 330 50 -80 3.00 0.4083
WVFGRD96 2.0 145 45 -85 3.08 0.4523
WVFGRD96 3.0 160 45 -65 3.09 0.3962
WVFGRD96 4.0 190 55 5 3.03 0.3896
WVFGRD96 5.0 190 45 5 3.11 0.3967
WVFGRD96 6.0 195 50 20 3.12 0.4023
WVFGRD96 7.0 5 80 45 3.12 0.4105
WVFGRD96 8.0 195 55 20 3.14 0.4183
WVFGRD96 9.0 5 75 40 3.13 0.4227
WVFGRD96 10.0 5 70 40 3.15 0.4250
WVFGRD96 11.0 5 70 40 3.16 0.4243
WVFGRD96 12.0 5 70 35 3.17 0.4212
WVFGRD96 13.0 195 60 20 3.20 0.4188
WVFGRD96 14.0 195 65 25 3.21 0.4167
WVFGRD96 15.0 195 60 45 3.24 0.4066
WVFGRD96 16.0 205 55 65 3.28 0.4020
WVFGRD96 17.0 210 55 70 3.29 0.3961
WVFGRD96 18.0 180 45 -25 3.28 0.3932
WVFGRD96 19.0 180 45 -25 3.28 0.3903
WVFGRD96 20.0 175 45 -30 3.29 0.3877
WVFGRD96 21.0 175 45 -30 3.30 0.3835
WVFGRD96 22.0 175 45 -35 3.31 0.3802
WVFGRD96 23.0 175 45 -35 3.32 0.3758
WVFGRD96 24.0 170 45 -40 3.32 0.3696
WVFGRD96 25.0 170 45 -40 3.33 0.3608
WVFGRD96 26.0 175 50 -35 3.33 0.3504
WVFGRD96 27.0 175 50 -30 3.33 0.3409
WVFGRD96 28.0 175 50 -30 3.34 0.3308
WVFGRD96 29.0 175 50 -30 3.35 0.3219
The best solution is
WVFGRD96 2.0 145 45 -85 3.08 0.4523
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 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=Tue Sep 22 09:49:51 CDT 2009