2009/04/09 20:47:01 42.493 13.305 10.0 3.10 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/09 20:47:01:0 42.49 13.31 10.0 3.1 Italy
Stations used:
IV.ASSB IV.CERT IV.CESX IV.FDMO IV.FIAM IV.INTR IV.LATE
IV.LPEL IV.MNS IV.MTCE IV.OFFI IV.RDP IV.RMP IV.SACS IV.SGG
IV.TERO MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 6.03e+20 dyne-cm
Mw = 3.12
Z = 7 km
Plane Strike Dip Rake
NP1 320 60 -75
NP2 112 33 -114
Principal Axes:
Axis Value Plunge Azimuth
T 6.03e+20 14 39
N 0.00e+00 13 132
P -6.03e+20 71 264
Moment Tensor: (dyne-cm)
Component Value
Mxx 3.41e+20
Mxy 2.72e+20
Mxz 1.27e+20
Myy 1.63e+20
Myz 2.73e+20
Mzz -5.04e+20
##############
######################
---##################### #
----------############### T ##
---------------############ ####
------------------##################
----------------------################
#-----------------------################
#-------------------------##############
##--------------------------##############
###----------- -------------############
###----------- P --------------###########
####---------- ---------------##########
####----------------------------########
######--------------------------########
######--------------------------######
########-----------------------####-
##########--------------------#---
#############------------####-
###########################-
######################
##############
Global CMT Convention Moment Tensor:
R T P
-5.04e+20 1.27e+20 -2.73e+20
1.27e+20 3.41e+20 -2.72e+20
-2.73e+20 -2.72e+20 1.63e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090409204701/index.html
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STK = 320
DIP = 60
RAKE = -75
MW = 3.12
HS = 7.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/09 20:47:01:0 42.49 13.31 10.0 3.1 Italy
Stations used:
IV.ASSB IV.CERT IV.CESX IV.FDMO IV.FIAM IV.INTR IV.LATE
IV.LPEL IV.MNS IV.MTCE IV.OFFI IV.RDP IV.RMP IV.SACS IV.SGG
IV.TERO MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 6.03e+20 dyne-cm
Mw = 3.12
Z = 7 km
Plane Strike Dip Rake
NP1 320 60 -75
NP2 112 33 -114
Principal Axes:
Axis Value Plunge Azimuth
T 6.03e+20 14 39
N 0.00e+00 13 132
P -6.03e+20 71 264
Moment Tensor: (dyne-cm)
Component Value
Mxx 3.41e+20
Mxy 2.72e+20
Mxz 1.27e+20
Myy 1.63e+20
Myz 2.73e+20
Mzz -5.04e+20
##############
######################
---##################### #
----------############### T ##
---------------############ ####
------------------##################
----------------------################
#-----------------------################
#-------------------------##############
##--------------------------##############
###----------- -------------############
###----------- P --------------###########
####---------- ---------------##########
####----------------------------########
######--------------------------########
######--------------------------######
########-----------------------####-
##########--------------------#---
#############------------####-
###########################-
######################
##############
Global CMT Convention Moment Tensor:
R T P
-5.04e+20 1.27e+20 -2.73e+20
1.27e+20 3.41e+20 -2.72e+20
-2.73e+20 -2.72e+20 1.63e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090409204701/index.html
|
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 0.5 300 40 -90 2.82 0.2966
WVFGRD96 1.0 125 50 -90 2.87 0.2701
WVFGRD96 2.0 345 90 -70 3.00 0.2871
WVFGRD96 3.0 320 80 -75 2.99 0.3730
WVFGRD96 4.0 315 75 -75 2.98 0.4252
WVFGRD96 5.0 330 75 -70 3.09 0.4674
WVFGRD96 6.0 325 65 -70 3.12 0.5119
WVFGRD96 7.0 320 60 -75 3.12 0.5349
WVFGRD96 8.0 320 60 -70 3.09 0.5343
WVFGRD96 9.0 320 60 -70 3.09 0.5268
WVFGRD96 10.0 320 60 -70 3.09 0.5127
WVFGRD96 11.0 325 65 -65 3.09 0.4968
WVFGRD96 12.0 325 65 -65 3.09 0.4800
WVFGRD96 13.0 325 70 -60 3.10 0.4633
WVFGRD96 14.0 325 70 -60 3.10 0.4458
WVFGRD96 15.0 325 70 -65 3.13 0.4319
WVFGRD96 16.0 325 70 -65 3.14 0.4157
WVFGRD96 17.0 325 70 -65 3.15 0.3986
WVFGRD96 18.0 325 70 -60 3.15 0.3836
WVFGRD96 19.0 325 70 -60 3.16 0.3686
WVFGRD96 20.0 325 70 -60 3.16 0.3551
WVFGRD96 21.0 335 75 -55 3.17 0.3433
WVFGRD96 22.0 340 80 -50 3.18 0.3333
WVFGRD96 23.0 340 80 -50 3.19 0.3255
WVFGRD96 24.0 340 80 -50 3.19 0.3181
WVFGRD96 25.0 340 80 -50 3.20 0.3096
WVFGRD96 26.0 340 80 -50 3.20 0.3007
WVFGRD96 27.0 320 70 -65 3.20 0.2916
WVFGRD96 28.0 335 75 -45 3.22 0.2846
WVFGRD96 29.0 325 70 -55 3.22 0.2810
The best solution is
WVFGRD96 7.0 320 60 -75 3.12 0.5349
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 Apr 30 13:29:13 CDT 2009