2009/04/06 16:06:18 42.234 13.483 10.6 2.9 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/06 16:06:18:0 42.23 13.48 10.6 2.9 Italy
Stations used:
IV.CERA IV.FIAM IV.GUAR IV.INTR IV.LPEL IV.MIDA IV.MTCE
IV.OFFI IV.TERO MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 5.25e+20 dyne-cm
Mw = 3.08
Z = 8 km
Plane Strike Dip Rake
NP1 160 70 -80
NP2 313 22 -116
Principal Axes:
Axis Value Plunge Azimuth
T 5.25e+20 24 242
N 0.00e+00 9 337
P -5.25e+20 64 86
Moment Tensor: (dyne-cm)
Component Value
Mxx 9.39e+19
Mxy 1.72e+20
Mxz -1.06e+20
Myy 2.38e+20
Myz -3.83e+20
Mzz -3.32e+20
##############
---#-------###########
-#####--------------########
#######-----------------######
#########-------------------######
##########---------------------#####
############---------------------#####
#############----------------------#####
#############-----------------------####
###############----------- ---------####
###############----------- P ----------###
################---------- ----------###
#################----------------------###
#### #########----------------------##
#### T ##########---------------------##
### ###########--------------------#
#################------------------#
#################----------------#
#################-------------
#################-----------
################------
##############
Global CMT Convention Moment Tensor:
R T P
-3.32e+20 -1.06e+20 3.83e+20
-1.06e+20 9.39e+19 -1.72e+20
3.83e+20 -1.72e+20 2.38e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090406160618/index.html
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STK = 160
DIP = 70
RAKE = -80
MW = 3.08
HS = 8.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/06 16:06:18:0 42.23 13.48 10.6 2.9 Italy
Stations used:
IV.CERA IV.FIAM IV.GUAR IV.INTR IV.LPEL IV.MIDA IV.MTCE
IV.OFFI IV.TERO MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 5.25e+20 dyne-cm
Mw = 3.08
Z = 8 km
Plane Strike Dip Rake
NP1 160 70 -80
NP2 313 22 -116
Principal Axes:
Axis Value Plunge Azimuth
T 5.25e+20 24 242
N 0.00e+00 9 337
P -5.25e+20 64 86
Moment Tensor: (dyne-cm)
Component Value
Mxx 9.39e+19
Mxy 1.72e+20
Mxz -1.06e+20
Myy 2.38e+20
Myz -3.83e+20
Mzz -3.32e+20
##############
---#-------###########
-#####--------------########
#######-----------------######
#########-------------------######
##########---------------------#####
############---------------------#####
#############----------------------#####
#############-----------------------####
###############----------- ---------####
###############----------- P ----------###
################---------- ----------###
#################----------------------###
#### #########----------------------##
#### T ##########---------------------##
### ###########--------------------#
#################------------------#
#################----------------#
#################-------------
#################-----------
################------
##############
Global CMT Convention Moment Tensor:
R T P
-3.32e+20 -1.06e+20 3.83e+20
-1.06e+20 9.39e+19 -1.72e+20
3.83e+20 -1.72e+20 2.38e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090406160618/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 1.0 180 35 -60 2.89 0.3232
WVFGRD96 2.0 180 35 -50 2.96 0.3467
WVFGRD96 3.0 170 90 -80 2.98 0.4054
WVFGRD96 4.0 165 80 -80 2.97 0.4681
WVFGRD96 5.0 165 80 -80 3.09 0.5206
WVFGRD96 6.0 160 75 -80 3.11 0.5689
WVFGRD96 7.0 160 70 -80 3.12 0.5998
WVFGRD96 8.0 160 70 -80 3.08 0.6084
WVFGRD96 9.0 160 70 -80 3.09 0.6068
WVFGRD96 10.0 160 70 -80 3.09 0.5987
WVFGRD96 11.0 160 70 -80 3.09 0.5867
WVFGRD96 12.0 160 70 -80 3.10 0.5728
WVFGRD96 13.0 160 70 -80 3.10 0.5573
WVFGRD96 14.0 160 70 -85 3.11 0.5401
WVFGRD96 15.0 160 70 -85 3.15 0.5260
WVFGRD96 16.0 160 70 -85 3.15 0.5072
WVFGRD96 17.0 -5 15 -80 3.16 0.4882
WVFGRD96 18.0 0 20 -70 3.17 0.4720
WVFGRD96 19.0 165 60 -65 3.15 0.4589
WVFGRD96 20.0 160 55 -70 3.16 0.4495
WVFGRD96 21.0 0 25 -70 3.18 0.4412
WVFGRD96 22.0 155 65 -100 3.19 0.4347
WVFGRD96 23.0 145 55 -95 3.20 0.4309
WVFGRD96 24.0 340 35 -75 3.21 0.4328
WVFGRD96 25.0 335 35 -80 3.22 0.4321
WVFGRD96 26.0 335 35 -80 3.22 0.4275
WVFGRD96 27.0 335 35 -80 3.23 0.4200
WVFGRD96 28.0 330 40 -80 3.25 0.4088
WVFGRD96 29.0 330 40 -80 3.27 0.4006
The best solution is
WVFGRD96 8.0 160 70 -80 3.08 0.6084
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=Mon May 17 14:06:40 CDT 2010