2009/07/23 22:37:32 42.251 13.500 9.4 3.00 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/07/23 22:37:32:0 42.25 13.50 9.4 3.0 Italy
Stations used:
IV.CAMP IV.CERT IV.CESX IV.FDMO IV.FIAM IV.GUAR IV.GUMA
IV.MIDA IV.MNS IV.MTCE IV.TERO IV.VVLD MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 1.01e+21 dyne-cm
Mw = 3.27
Z = 9 km
Plane Strike Dip Rake
NP1 145 60 -60
NP2 276 41 -131
Principal Axes:
Axis Value Plunge Azimuth
T 1.01e+21 10 214
N 0.00e+00 26 309
P -1.01e+21 62 104
Moment Tensor: (dyne-cm)
Component Value
Mxx 6.61e+20
Mxy 5.06e+20
Mxz -4.41e+19
Myy 9.75e+19
Myz -5.04e+20
Mzz -7.59e+20
##############
######################
--##########################
---###########################
-----########-----################
------#--------------------#########
----###------------------------#######
---######--------------------------#####
-########----------------------------###
-##########----------------------------###
############-------------- -----------##
#############------------- P ------------#
##############------------ -------------
##############--------------------------
###############-------------------------
################----------------------
#################-------------------
##################----------------
### ############------------
## T ################-------
####################
##############
Global CMT Convention Moment Tensor:
R T P
-7.59e+20 -4.41e+19 5.04e+20
-4.41e+19 6.61e+20 -5.06e+20
5.04e+20 -5.06e+20 9.75e+19
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090723223732/index.html
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STK = 145
DIP = 60
RAKE = -60
MW = 3.27
HS = 9.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/07/23 22:37:32:0 42.25 13.50 9.4 3.0 Italy
Stations used:
IV.CAMP IV.CERT IV.CESX IV.FDMO IV.FIAM IV.GUAR IV.GUMA
IV.MIDA IV.MNS IV.MTCE IV.TERO IV.VVLD MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 1.01e+21 dyne-cm
Mw = 3.27
Z = 9 km
Plane Strike Dip Rake
NP1 145 60 -60
NP2 276 41 -131
Principal Axes:
Axis Value Plunge Azimuth
T 1.01e+21 10 214
N 0.00e+00 26 309
P -1.01e+21 62 104
Moment Tensor: (dyne-cm)
Component Value
Mxx 6.61e+20
Mxy 5.06e+20
Mxz -4.41e+19
Myy 9.75e+19
Myz -5.04e+20
Mzz -7.59e+20
##############
######################
--##########################
---###########################
-----########-----################
------#--------------------#########
----###------------------------#######
---######--------------------------#####
-########----------------------------###
-##########----------------------------###
############-------------- -----------##
#############------------- P ------------#
##############------------ -------------
##############--------------------------
###############-------------------------
################----------------------
#################-------------------
##################----------------
### ############------------
## T ################-------
####################
##############
Global CMT Convention Moment Tensor:
R T P
-7.59e+20 -4.41e+19 5.04e+20
-4.41e+19 6.61e+20 -5.06e+20
5.04e+20 -5.06e+20 9.75e+19
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090723223732/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 0.5 185 35 75 3.02 0.4045
WVFGRD96 1.0 175 50 65 3.04 0.3870
WVFGRD96 2.0 -5 75 70 3.15 0.4409
WVFGRD96 3.0 355 80 65 3.14 0.4859
WVFGRD96 4.0 165 90 -55 3.13 0.5206
WVFGRD96 5.0 165 90 -60 3.23 0.5510
WVFGRD96 6.0 155 75 -60 3.25 0.5887
WVFGRD96 7.0 150 65 -60 3.28 0.6182
WVFGRD96 8.0 145 60 -60 3.26 0.6290
WVFGRD96 9.0 145 60 -60 3.27 0.6291
WVFGRD96 10.0 145 60 -60 3.27 0.6237
WVFGRD96 11.0 145 60 -60 3.28 0.6142
WVFGRD96 12.0 145 60 -60 3.29 0.6022
WVFGRD96 13.0 145 60 -60 3.29 0.5863
WVFGRD96 14.0 145 60 -60 3.30 0.5683
WVFGRD96 15.0 145 60 -65 3.34 0.5532
WVFGRD96 16.0 145 60 -60 3.34 0.5333
WVFGRD96 17.0 145 60 -60 3.34 0.5118
WVFGRD96 18.0 150 60 -55 3.34 0.4901
WVFGRD96 19.0 150 60 -55 3.34 0.4701
WVFGRD96 20.0 145 55 -55 3.34 0.4543
WVFGRD96 21.0 145 50 -55 3.34 0.4425
WVFGRD96 22.0 145 50 -55 3.35 0.4348
WVFGRD96 23.0 145 50 -55 3.36 0.4278
WVFGRD96 24.0 140 45 -60 3.37 0.4203
WVFGRD96 25.0 140 45 -60 3.37 0.4101
WVFGRD96 26.0 140 45 -65 3.38 0.3970
WVFGRD96 27.0 160 40 40 3.43 0.3891
WVFGRD96 28.0 160 40 45 3.45 0.3893
WVFGRD96 29.0 160 40 45 3.46 0.3880
The best solution is
WVFGRD96 9.0 145 60 -60 3.27 0.6291
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=Fri Jul 24 09:28:56 CDT 2009