2009/08/06 15:36:44 41.632 13.666 11.1 3.90 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/08/06 15:36:44:0 41.63 13.67 11.1 3.9 Italy
Stations used:
IV.BSSO IV.CAFR IV.CERA IV.CERT IV.CESX IV.FDMO IV.FIAM
IV.FRES IV.GIUL IV.GUAR IV.INTR IV.LAV9 IV.LNSS IV.MIDA
IV.MODR IV.OFFI IV.PTRJ IV.RDP IV.RMP IV.RNI2 IV.SACR
IV.SGG IV.SGRT IV.TOLF IV.TRIV IV.VAGA MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 1.55e+22 dyne-cm
Mw = 4.06
Z = 13 km
Plane Strike Dip Rake
NP1 350 65 -50
NP2 107 46 -144
Principal Axes:
Axis Value Plunge Azimuth
T 1.55e+22 11 52
N 0.00e+00 36 150
P -1.55e+22 52 308
Moment Tensor: (dyne-cm)
Component Value
Mxx 3.36e+21
Mxy 1.00e+22
Mxz -2.82e+21
Myy 5.73e+21
Myz 8.24e+21
Mzz -9.09e+21
-----#########
----------############
---------------#############
-----------------###########
--------------------########## T #
----------------------######### ##
---------- ----------###############
----------- P -----------###############
----------- -----------###############
##-------------------------###############
###------------------------###############
####------------------------##############
#####-----------------------##############
######---------------------#############
#########------------------############-
###########---------------##########--
##############-----------######-----
########################----------
#####################---------
####################--------
################------
###########---
Global CMT Convention Moment Tensor:
R T P
-9.09e+21 -2.82e+21 -8.24e+21
-2.82e+21 3.36e+21 -1.00e+22
-8.24e+21 -1.00e+22 5.73e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090806153644/index.html
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STK = 350
DIP = 65
RAKE = -50
MW = 4.06
HS = 13.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/08/06 15:36:44:0 41.63 13.67 11.1 3.9 Italy
Stations used:
IV.BSSO IV.CAFR IV.CERA IV.CERT IV.CESX IV.FDMO IV.FIAM
IV.FRES IV.GIUL IV.GUAR IV.INTR IV.LAV9 IV.LNSS IV.MIDA
IV.MODR IV.OFFI IV.PTRJ IV.RDP IV.RMP IV.RNI2 IV.SACR
IV.SGG IV.SGRT IV.TOLF IV.TRIV IV.VAGA MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 1.55e+22 dyne-cm
Mw = 4.06
Z = 13 km
Plane Strike Dip Rake
NP1 350 65 -50
NP2 107 46 -144
Principal Axes:
Axis Value Plunge Azimuth
T 1.55e+22 11 52
N 0.00e+00 36 150
P -1.55e+22 52 308
Moment Tensor: (dyne-cm)
Component Value
Mxx 3.36e+21
Mxy 1.00e+22
Mxz -2.82e+21
Myy 5.73e+21
Myz 8.24e+21
Mzz -9.09e+21
-----#########
----------############
---------------#############
-----------------###########
--------------------########## T #
----------------------######### ##
---------- ----------###############
----------- P -----------###############
----------- -----------###############
##-------------------------###############
###------------------------###############
####------------------------##############
#####-----------------------##############
######---------------------#############
#########------------------############-
###########---------------##########--
##############-----------######-----
########################----------
#####################---------
####################--------
################------
###########---
Global CMT Convention Moment Tensor:
R T P
-9.09e+21 -2.82e+21 -8.24e+21
-2.82e+21 3.36e+21 -1.00e+22
-8.24e+21 -1.00e+22 5.73e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090806153644/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 45 90 3.76 0.2847
WVFGRD96 1.0 35 45 85 3.78 0.2800
WVFGRD96 2.0 20 55 70 3.85 0.2735
WVFGRD96 3.0 185 90 55 3.85 0.3004
WVFGRD96 4.0 0 85 -50 3.86 0.3504
WVFGRD96 5.0 360 85 -55 3.96 0.3934
WVFGRD96 6.0 -5 80 -55 3.98 0.4326
WVFGRD96 7.0 -10 75 -55 4.00 0.4635
WVFGRD96 8.0 350 70 -50 3.99 0.4875
WVFGRD96 9.0 350 70 -50 4.00 0.5041
WVFGRD96 10.0 350 70 -50 4.02 0.5155
WVFGRD96 11.0 350 65 -50 4.04 0.5228
WVFGRD96 12.0 350 65 -50 4.05 0.5261
WVFGRD96 13.0 350 65 -50 4.06 0.5261
WVFGRD96 14.0 350 65 -50 4.07 0.5230
WVFGRD96 15.0 350 65 -50 4.11 0.5187
WVFGRD96 16.0 350 65 -50 4.12 0.5100
WVFGRD96 17.0 350 65 -50 4.13 0.4984
WVFGRD96 18.0 350 65 -50 4.14 0.4843
WVFGRD96 19.0 350 65 -50 4.14 0.4681
WVFGRD96 20.0 350 65 -50 4.15 0.4496
WVFGRD96 21.0 350 60 -50 4.16 0.4312
WVFGRD96 22.0 350 60 -50 4.16 0.4120
WVFGRD96 23.0 350 55 -50 4.17 0.3939
WVFGRD96 24.0 345 50 -60 4.18 0.3767
WVFGRD96 25.0 345 50 -60 4.18 0.3619
WVFGRD96 26.0 190 75 45 4.16 0.3492
WVFGRD96 27.0 185 80 40 4.17 0.3395
WVFGRD96 28.0 185 80 40 4.17 0.3320
WVFGRD96 29.0 190 75 40 4.19 0.3261
The best solution is
WVFGRD96 13.0 350 65 -50 4.06 0.5261
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=Thu Aug 6 11:37:52 CDT 2009