2009/04/24 15:53:45 42.309 13.465 10.5 3.00 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/24 15:53:45:0 42.31 13.47 10.5 3.0 Italy
Stations used:
IV.CERT IV.CING IV.FDMO IV.FIAM IV.GIUL IV.GUAR IV.GUMA
IV.LPEL IV.MNS IV.MTCE IV.OFFI IV.TERO
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 7.67e+20 dyne-cm
Mw = 3.19
Z = 6 km
Plane Strike Dip Rake
NP1 132 70 -105
NP2 350 25 -55
Principal Axes:
Axis Value Plunge Azimuth
T 7.67e+20 23 234
N 0.00e+00 14 138
P -7.67e+20 62 19
Moment Tensor: (dyne-cm)
Component Value
Mxx 7.81e+19
Mxy 2.57e+20
Mxz -4.63e+20
Myy 4.03e+20
Myz -3.29e+20
Mzz -4.82e+20
---------#####
-----------------#####
----------------------######
-------------------------#####
##---------------------------#####
####---------------------------#####
######-------------- ----------#####
########------------- P -----------#####
#########------------ -----------#####
###########--------------------------#####
#############------------------------#####
###############----------------------#####
################---------------------#####
#################-------------------####
####################---------------#####
##### #############-------------####
#### T ################---------####
### ####################----####
###########################---
########################----
###################---
#############-
Global CMT Convention Moment Tensor:
R T P
-4.82e+20 -4.63e+20 3.29e+20
-4.63e+20 7.81e+19 -2.57e+20
3.29e+20 -2.57e+20 4.03e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090424155345/index.html
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STK = 350
DIP = 25
RAKE = -55
MW = 3.19
HS = 6.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/24 15:53:45:0 42.31 13.47 10.5 3.0 Italy
Stations used:
IV.CERT IV.CING IV.FDMO IV.FIAM IV.GIUL IV.GUAR IV.GUMA
IV.LPEL IV.MNS IV.MTCE IV.OFFI IV.TERO
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 7.67e+20 dyne-cm
Mw = 3.19
Z = 6 km
Plane Strike Dip Rake
NP1 132 70 -105
NP2 350 25 -55
Principal Axes:
Axis Value Plunge Azimuth
T 7.67e+20 23 234
N 0.00e+00 14 138
P -7.67e+20 62 19
Moment Tensor: (dyne-cm)
Component Value
Mxx 7.81e+19
Mxy 2.57e+20
Mxz -4.63e+20
Myy 4.03e+20
Myz -3.29e+20
Mzz -4.82e+20
---------#####
-----------------#####
----------------------######
-------------------------#####
##---------------------------#####
####---------------------------#####
######-------------- ----------#####
########------------- P -----------#####
#########------------ -----------#####
###########--------------------------#####
#############------------------------#####
###############----------------------#####
################---------------------#####
#################-------------------####
####################---------------#####
##### #############-------------####
#### T ################---------####
### ####################----####
###########################---
########################----
###################---
#############-
Global CMT Convention Moment Tensor:
R T P
-4.82e+20 -4.63e+20 3.29e+20
-4.63e+20 7.81e+19 -2.57e+20
3.29e+20 -2.57e+20 4.03e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090424155345/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 35 -75 2.93 0.2871
WVFGRD96 1.0 330 40 -70 2.96 0.2661
WVFGRD96 2.0 345 10 -60 3.14 0.3233
WVFGRD96 3.0 -10 15 -55 3.11 0.3874
WVFGRD96 4.0 340 20 -65 3.09 0.4160
WVFGRD96 5.0 340 20 -65 3.19 0.4369
WVFGRD96 6.0 350 25 -55 3.19 0.4374
WVFGRD96 7.0 345 25 -60 3.19 0.4269
WVFGRD96 8.0 355 30 -50 3.14 0.4020
WVFGRD96 9.0 355 30 -45 3.14 0.3839
WVFGRD96 10.0 0 35 -40 3.15 0.3663
WVFGRD96 11.0 0 35 -40 3.15 0.3486
WVFGRD96 12.0 5 35 -35 3.16 0.3307
WVFGRD96 13.0 0 35 -40 3.16 0.3119
WVFGRD96 14.0 15 40 -25 3.17 0.2932
WVFGRD96 15.0 5 35 -30 3.20 0.2784
WVFGRD96 16.0 345 40 -60 3.20 0.2620
WVFGRD96 17.0 335 40 -70 3.20 0.2516
WVFGRD96 18.0 335 40 -70 3.21 0.2422
WVFGRD96 19.0 340 45 -65 3.21 0.2337
WVFGRD96 20.0 340 45 -65 3.22 0.2253
WVFGRD96 21.0 165 45 -55 3.21 0.2167
WVFGRD96 22.0 310 55 80 3.22 0.2140
WVFGRD96 23.0 315 55 85 3.23 0.2171
WVFGRD96 24.0 315 55 85 3.24 0.2209
WVFGRD96 25.0 315 60 80 3.25 0.2273
WVFGRD96 26.0 325 45 100 3.28 0.2358
WVFGRD96 27.0 130 45 80 3.30 0.2438
WVFGRD96 28.0 130 45 80 3.32 0.2476
WVFGRD96 29.0 325 45 100 3.33 0.2444
The best solution is
WVFGRD96 6.0 350 25 -55 3.19 0.4374
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 May 1 14:38:33 CDT 2009