2009/05/11 16:59:04 42.491 13.366 9.8 3.1 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/05/11 16:59:04:0 42.49 13.37 9.8 3.1 Italy
Stations used:
IV.CERT IV.CESI IV.CESX IV.CING IV.FDMO IV.FIAM IV.GUMA
IV.MNS IV.OFFI IV.SACS IV.TERO IV.TRIV MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 9.44e+20 dyne-cm
Mw = 3.25
Z = 7 km
Plane Strike Dip Rake
NP1 316 64 -106
NP2 170 30 -60
Principal Axes:
Axis Value Plunge Azimuth
T 9.44e+20 18 58
N 0.00e+00 14 323
P -9.44e+20 67 197
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.02e+20
Mxy 3.43e+20
Mxz 4.74e+20
Myy 6.06e+20
Myz 3.32e+20
Mzz -7.08e+20
--############
---###################
----########################
####--########################
#####-------######################
#####-----------############### ##
#####---------------############ T ###
######-----------------########## ####
#####--------------------###############
######---------------------###############
######-----------------------#############
######------------------------############
#######----------- ----------###########
######----------- P -----------#########
#######---------- ------------########
######--------------------------######
######--------------------------####
#######------------------------###
######-----------------------#
#######---------------------
######----------------
######--------
Global CMT Convention Moment Tensor:
R T P
-7.08e+20 4.74e+20 -3.32e+20
4.74e+20 1.02e+20 -3.43e+20
-3.32e+20 -3.43e+20 6.06e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090511165904/index.html
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STK = 170
DIP = 30
RAKE = -60
MW = 3.25
HS = 7.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/05/11 16:59:04:0 42.49 13.37 9.8 3.1 Italy
Stations used:
IV.CERT IV.CESI IV.CESX IV.CING IV.FDMO IV.FIAM IV.GUMA
IV.MNS IV.OFFI IV.SACS IV.TERO IV.TRIV MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 9.44e+20 dyne-cm
Mw = 3.25
Z = 7 km
Plane Strike Dip Rake
NP1 316 64 -106
NP2 170 30 -60
Principal Axes:
Axis Value Plunge Azimuth
T 9.44e+20 18 58
N 0.00e+00 14 323
P -9.44e+20 67 197
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.02e+20
Mxy 3.43e+20
Mxz 4.74e+20
Myy 6.06e+20
Myz 3.32e+20
Mzz -7.08e+20
--############
---###################
----########################
####--########################
#####-------######################
#####-----------############### ##
#####---------------############ T ###
######-----------------########## ####
#####--------------------###############
######---------------------###############
######-----------------------#############
######------------------------############
#######----------- ----------###########
######----------- P -----------#########
#######---------- ------------########
######--------------------------######
######--------------------------####
#######------------------------###
######-----------------------#
#######---------------------
######----------------
######--------
Global CMT Convention Moment Tensor:
R T P
-7.08e+20 4.74e+20 -3.32e+20
4.74e+20 1.02e+20 -3.43e+20
-3.32e+20 -3.43e+20 6.06e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090511165904/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 0.5 330 40 -85 2.98 0.3666
WVFGRD96 1.0 150 50 -85 3.01 0.3237
WVFGRD96 2.0 185 20 -30 3.14 0.3672
WVFGRD96 3.0 185 25 -35 3.13 0.4561
WVFGRD96 4.0 185 30 -40 3.13 0.5096
WVFGRD96 5.0 175 25 -50 3.23 0.5585
WVFGRD96 6.0 170 30 -60 3.25 0.5835
WVFGRD96 7.0 170 30 -60 3.25 0.5938
WVFGRD96 8.0 170 35 -60 3.22 0.5814
WVFGRD96 9.0 175 35 -50 3.22 0.5722
WVFGRD96 10.0 170 35 -55 3.23 0.5570
WVFGRD96 11.0 180 40 -40 3.23 0.5408
WVFGRD96 12.0 180 40 -40 3.24 0.5215
WVFGRD96 13.0 185 40 -35 3.24 0.4990
WVFGRD96 14.0 185 40 -35 3.24 0.4806
WVFGRD96 15.0 190 40 -25 3.27 0.4679
WVFGRD96 16.0 190 40 -25 3.28 0.4503
WVFGRD96 17.0 190 40 -25 3.29 0.4332
WVFGRD96 18.0 190 40 -25 3.29 0.4164
WVFGRD96 19.0 190 40 -20 3.30 0.4010
WVFGRD96 20.0 190 40 -20 3.30 0.3869
WVFGRD96 21.0 190 40 -20 3.31 0.3740
WVFGRD96 22.0 185 45 -25 3.32 0.3624
WVFGRD96 23.0 185 45 -25 3.33 0.3548
WVFGRD96 24.0 185 45 -25 3.33 0.3498
WVFGRD96 25.0 185 45 -25 3.34 0.3460
WVFGRD96 26.0 185 45 -25 3.35 0.3413
WVFGRD96 27.0 185 45 -25 3.35 0.3343
WVFGRD96 28.0 185 45 -25 3.36 0.3256
WVFGRD96 29.0 215 45 20 3.36 0.3250
The best solution is
WVFGRD96 7.0 170 30 -60 3.25 0.5938
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=Sun Aug 23 14:09:24 CDT 2009