2009/04/09 04:29:45 42.504 13.345 11.0 3.20 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/09 04:29:45:0 42.50 13.35 11.0 3.2 Italy
Stations used:
IV.ASSB IV.CERT IV.CESX IV.FDMO IV.FIAM IV.MNS IV.MTCE
IV.OFFI IV.SACS IV.TERO IV.TRTR MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 5.82e+20 dyne-cm
Mw = 3.11
Z = 7 km
Plane Strike Dip Rake
NP1 330 55 -70
NP2 118 40 -116
Principal Axes:
Axis Value Plunge Azimuth
T 5.82e+20 8 46
N 0.00e+00 16 138
P -5.82e+20 72 291
Moment Tensor: (dyne-cm)
Component Value
Mxx 2.70e+20
Mxy 3.04e+20
Mxz -5.35e+18
Myy 2.44e+20
Myz 2.19e+20
Mzz -5.14e+20
##############
---###################
-----------###############
--------------############# T
-------------------########## ##
---------------------###############
#-----------------------##############
##------------------------##############
##--------------------------############
###-------------- ----------############
####------------- P ----------############
#####------------ -----------###########
######--------------------------##########
######-------------------------#########
########------------------------########
#########----------------------#######
###########-------------------######
#############----------------###--
###################----####---
#########################---
######################
##############
Global CMT Convention Moment Tensor:
R T P
-5.14e+20 -5.35e+18 -2.19e+20
-5.35e+18 2.70e+20 -3.04e+20
-2.19e+20 -3.04e+20 2.44e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090409042945/index.html
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STK = 330
DIP = 55
RAKE = -70
MW = 3.11
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 04:29:45:0 42.50 13.35 11.0 3.2 Italy
Stations used:
IV.ASSB IV.CERT IV.CESX IV.FDMO IV.FIAM IV.MNS IV.MTCE
IV.OFFI IV.SACS IV.TERO IV.TRTR MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 5.82e+20 dyne-cm
Mw = 3.11
Z = 7 km
Plane Strike Dip Rake
NP1 330 55 -70
NP2 118 40 -116
Principal Axes:
Axis Value Plunge Azimuth
T 5.82e+20 8 46
N 0.00e+00 16 138
P -5.82e+20 72 291
Moment Tensor: (dyne-cm)
Component Value
Mxx 2.70e+20
Mxy 3.04e+20
Mxz -5.35e+18
Myy 2.44e+20
Myz 2.19e+20
Mzz -5.14e+20
##############
---###################
-----------###############
--------------############# T
-------------------########## ##
---------------------###############
#-----------------------##############
##------------------------##############
##--------------------------############
###-------------- ----------############
####------------- P ----------############
#####------------ -----------###########
######--------------------------##########
######-------------------------#########
########------------------------########
#########----------------------#######
###########-------------------######
#############----------------###--
###################----####---
#########################---
######################
##############
Global CMT Convention Moment Tensor:
R T P
-5.14e+20 -5.35e+18 -2.19e+20
-5.35e+18 2.70e+20 -3.04e+20
-2.19e+20 -3.04e+20 2.44e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090409042945/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 0.5 345 45 -45 2.82 0.2987
WVFGRD96 1.0 345 45 -45 2.84 0.2857
WVFGRD96 2.0 200 20 -10 2.98 0.3180
WVFGRD96 3.0 195 25 -15 2.97 0.3877
WVFGRD96 4.0 185 35 -30 2.98 0.4371
WVFGRD96 5.0 170 30 -50 3.08 0.4820
WVFGRD96 6.0 325 55 -80 3.12 0.5391
WVFGRD96 7.0 330 55 -70 3.11 0.5558
WVFGRD96 8.0 320 50 -85 3.09 0.5385
WVFGRD96 9.0 330 55 -70 3.08 0.5212
WVFGRD96 10.0 175 45 -45 3.09 0.5037
WVFGRD96 11.0 180 50 -35 3.10 0.4883
WVFGRD96 12.0 180 50 -35 3.10 0.4714
WVFGRD96 13.0 175 55 -30 3.12 0.4527
WVFGRD96 14.0 175 55 -30 3.13 0.4319
WVFGRD96 15.0 175 55 -30 3.15 0.4180
WVFGRD96 16.0 175 60 -25 3.16 0.4003
WVFGRD96 17.0 175 60 -25 3.16 0.3840
WVFGRD96 18.0 175 60 -25 3.17 0.3685
WVFGRD96 19.0 175 60 -25 3.18 0.3519
WVFGRD96 20.0 180 65 -15 3.17 0.3389
WVFGRD96 21.0 180 65 -15 3.18 0.3307
WVFGRD96 22.0 180 70 -10 3.19 0.3230
WVFGRD96 23.0 180 70 -5 3.19 0.3162
WVFGRD96 24.0 180 70 -5 3.20 0.3090
WVFGRD96 25.0 180 55 -20 3.21 0.3033
WVFGRD96 26.0 180 50 -20 3.21 0.3003
WVFGRD96 27.0 185 50 -20 3.21 0.2963
WVFGRD96 28.0 200 55 15 3.20 0.2947
WVFGRD96 29.0 200 55 15 3.22 0.2986
The best solution is
WVFGRD96 7.0 330 55 -70 3.11 0.5558
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 08:39:28 CDT 2009