2009/04/25 13:17:31 42.264 13.495 10.9 3.0 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/25 13:17:31:0 42.26 13.49 10.9 3.0 Italy
Stations used:
IV.CERT IV.CESX IV.FIAM IV.GUAR IV.LATE IV.LPEL IV.MNS
IV.MTCE IV.RMP IV.TERO MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 6.24e+20 dyne-cm
Mw = 3.13
Z = 10 km
Plane Strike Dip Rake
NP1 145 50 -75
NP2 302 42 -107
Principal Axes:
Axis Value Plunge Azimuth
T 6.24e+20 4 224
N 0.00e+00 11 315
P -6.24e+20 78 116
Moment Tensor: (dyne-cm)
Component Value
Mxx 3.11e+20
Mxy 3.21e+20
Mxz 2.50e+19
Myy 2.82e+20
Myz -1.45e+20
Mzz -5.93e+20
##############
######################
--##########################
--###------###################
-###----------------##############
#####-------------------############
######----------------------##########
#######------------------------#########
#######--------------------------#######
#########--------------------------#######
#########------------- -----------######
##########------------ P ------------#####
###########----------- -------------####
###########--------------------------###
############--------------------------##
#############------------------------#
##############----------------------
# ###########-------------------
T #############---------------
#################----------
######################
##############
Global CMT Convention Moment Tensor:
R T P
-5.93e+20 2.50e+19 1.45e+20
2.50e+19 3.11e+20 -3.21e+20
1.45e+20 -3.21e+20 2.82e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090425131731/index.html
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STK = 145
DIP = 50
RAKE = -75
MW = 3.13
HS = 10.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/25 13:17:31:0 42.26 13.49 10.9 3.0 Italy
Stations used:
IV.CERT IV.CESX IV.FIAM IV.GUAR IV.LATE IV.LPEL IV.MNS
IV.MTCE IV.RMP IV.TERO MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 6.24e+20 dyne-cm
Mw = 3.13
Z = 10 km
Plane Strike Dip Rake
NP1 145 50 -75
NP2 302 42 -107
Principal Axes:
Axis Value Plunge Azimuth
T 6.24e+20 4 224
N 0.00e+00 11 315
P -6.24e+20 78 116
Moment Tensor: (dyne-cm)
Component Value
Mxx 3.11e+20
Mxy 3.21e+20
Mxz 2.50e+19
Myy 2.82e+20
Myz -1.45e+20
Mzz -5.93e+20
##############
######################
--##########################
--###------###################
-###----------------##############
#####-------------------############
######----------------------##########
#######------------------------#########
#######--------------------------#######
#########--------------------------#######
#########------------- -----------######
##########------------ P ------------#####
###########----------- -------------####
###########--------------------------###
############--------------------------##
#############------------------------#
##############----------------------
# ###########-------------------
T #############---------------
#################----------
######################
##############
Global CMT Convention Moment Tensor:
R T P
-5.93e+20 2.50e+19 1.45e+20
2.50e+19 3.11e+20 -3.21e+20
1.45e+20 -3.21e+20 2.82e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090425131731/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 0.5 330 35 90 2.90 0.4112
WVFGRD96 1.0 320 30 75 2.95 0.3586
WVFGRD96 2.0 0 80 65 2.97 0.3541
WVFGRD96 3.0 170 90 -65 2.97 0.4138
WVFGRD96 4.0 350 90 60 2.95 0.4632
WVFGRD96 5.0 165 80 -65 3.07 0.5070
WVFGRD96 6.0 155 65 -70 3.12 0.5646
WVFGRD96 7.0 150 60 -75 3.14 0.6206
WVFGRD96 8.0 145 50 -75 3.13 0.6579
WVFGRD96 9.0 145 50 -75 3.13 0.6690
WVFGRD96 10.0 145 50 -75 3.13 0.6692
WVFGRD96 11.0 145 50 -75 3.14 0.6624
WVFGRD96 12.0 145 50 -75 3.15 0.6493
WVFGRD96 13.0 145 50 -75 3.15 0.6311
WVFGRD96 14.0 140 50 -80 3.17 0.6092
WVFGRD96 15.0 145 50 -80 3.20 0.5891
WVFGRD96 16.0 150 50 -75 3.20 0.5656
WVFGRD96 17.0 145 45 -75 3.20 0.5408
WVFGRD96 18.0 165 45 -60 3.20 0.5172
WVFGRD96 19.0 170 45 -55 3.20 0.4950
WVFGRD96 20.0 170 45 -55 3.21 0.4740
WVFGRD96 21.0 195 55 -40 3.23 0.4546
WVFGRD96 22.0 195 55 -40 3.24 0.4357
WVFGRD96 23.0 150 45 -55 3.23 0.4213
WVFGRD96 24.0 150 45 -60 3.23 0.4077
WVFGRD96 25.0 20 70 25 3.38 0.4023
WVFGRD96 26.0 20 70 25 3.39 0.4037
WVFGRD96 27.0 20 75 25 3.40 0.4056
WVFGRD96 28.0 20 75 25 3.41 0.4066
WVFGRD96 29.0 20 75 20 3.44 0.4092
The best solution is
WVFGRD96 10.0 145 50 -75 3.13 0.6692
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=Wed Sep 2 07:56:53 CDT 2009