2009/04/13 07:08:30 42.268 13.484 9.3 3.10 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/13 07:08:30:0 42.27 13.48 9.3 3.1 Italy
Stations used:
IV.CERT IV.FIAM IV.INTR IV.LPEL IV.MNS IV.MTCE IV.POFI
MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 8.81e+20 dyne-cm
Mw = 3.23
Z = 7 km
Plane Strike Dip Rake
NP1 140 55 -75
NP2 295 38 -110
Principal Axes:
Axis Value Plunge Azimuth
T 8.81e+20 9 219
N 0.00e+00 12 311
P -8.81e+20 75 94
Moment Tensor: (dyne-cm)
Component Value
Mxx 5.14e+20
Mxy 4.26e+20
Mxz -8.69e+19
Myy 2.85e+20
Myz -3.07e+20
Mzz -8.00e+20
##############
######################
-###########################
-######------#################
----------------------############
-###----------------------##########
#####-------------------------########
#######--------------------------#######
#######---------------------------######
#########----------------------------#####
##########-------------- -----------####
###########------------- P ------------###
############------------ ------------###
############---------------------------#
##############-------------------------#
###############-----------------------
################--------------------
### ###########-----------------
# T ###############-----------
####################-----
######################
##############
Global CMT Convention Moment Tensor:
R T P
-8.00e+20 -8.69e+19 3.07e+20
-8.69e+19 5.14e+20 -4.26e+20
3.07e+20 -4.26e+20 2.85e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090413070830/index.html
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STK = 140
DIP = 55
RAKE = -75
MW = 3.23
HS = 7.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/13 07:08:30:0 42.27 13.48 9.3 3.1 Italy
Stations used:
IV.CERT IV.FIAM IV.INTR IV.LPEL IV.MNS IV.MTCE IV.POFI
MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 8.81e+20 dyne-cm
Mw = 3.23
Z = 7 km
Plane Strike Dip Rake
NP1 140 55 -75
NP2 295 38 -110
Principal Axes:
Axis Value Plunge Azimuth
T 8.81e+20 9 219
N 0.00e+00 12 311
P -8.81e+20 75 94
Moment Tensor: (dyne-cm)
Component Value
Mxx 5.14e+20
Mxy 4.26e+20
Mxz -8.69e+19
Myy 2.85e+20
Myz -3.07e+20
Mzz -8.00e+20
##############
######################
-###########################
-######------#################
----------------------############
-###----------------------##########
#####-------------------------########
#######--------------------------#######
#######---------------------------######
#########----------------------------#####
##########-------------- -----------####
###########------------- P ------------###
############------------ ------------###
############---------------------------#
##############-------------------------#
###############-----------------------
################--------------------
### ###########-----------------
# T ###############-----------
####################-----
######################
##############
Global CMT Convention Moment Tensor:
R T P
-8.00e+20 -8.69e+19 3.07e+20
-8.69e+19 5.14e+20 -4.26e+20
3.07e+20 -4.26e+20 2.85e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090413070830/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 0.5 185 65 -35 2.95 0.3391
WVFGRD96 1.0 185 60 -35 2.97 0.3444
WVFGRD96 2.0 180 45 -35 3.05 0.3569
WVFGRD96 3.0 165 80 -65 3.08 0.4112
WVFGRD96 4.0 155 70 -65 3.09 0.4467
WVFGRD96 5.0 150 65 -75 3.22 0.4814
WVFGRD96 6.0 145 60 -75 3.23 0.5111
WVFGRD96 7.0 140 55 -75 3.23 0.5111
WVFGRD96 8.0 140 55 -75 3.19 0.4952
WVFGRD96 9.0 135 55 -75 3.20 0.4793
WVFGRD96 10.0 135 55 -75 3.20 0.4630
WVFGRD96 11.0 135 55 -75 3.20 0.4452
WVFGRD96 12.0 135 55 -75 3.20 0.4284
WVFGRD96 13.0 135 55 -75 3.21 0.4100
WVFGRD96 14.0 135 50 -70 3.20 0.3900
WVFGRD96 15.0 135 50 -70 3.23 0.3780
WVFGRD96 16.0 130 45 -70 3.23 0.3664
WVFGRD96 17.0 135 45 -65 3.23 0.3570
WVFGRD96 18.0 135 45 -65 3.24 0.3466
WVFGRD96 19.0 130 40 -65 3.25 0.3388
WVFGRD96 20.0 130 40 -65 3.26 0.3302
WVFGRD96 21.0 130 40 -65 3.26 0.3202
WVFGRD96 22.0 300 75 -65 3.35 0.3144
WVFGRD96 23.0 300 75 -65 3.36 0.3129
WVFGRD96 24.0 300 75 -65 3.36 0.3108
WVFGRD96 25.0 300 75 -65 3.37 0.3072
WVFGRD96 26.0 295 70 -65 3.37 0.3026
WVFGRD96 27.0 190 25 15 3.33 0.2977
WVFGRD96 28.0 190 30 20 3.33 0.2974
WVFGRD96 29.0 190 35 25 3.33 0.2978
The best solution is
WVFGRD96 7.0 140 55 -75 3.23 0.5111
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 Apr 29 17:04:02 CDT 2009