2009/04/07 10:29:10 42.331 13.406 9.7 3.1 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/07 10:29:10:7 42.33 13.41 9.7 3.1 Italy
Stations used:
IV.FIAM IV.GUAR IV.MNS IV.OFFI
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 6.46e+20 dyne-cm
Mw = 3.14
Z = 7 km
Plane Strike Dip Rake
NP1 160 60 -75
NP2 312 33 -114
Principal Axes:
Axis Value Plunge Azimuth
T 6.46e+20 14 239
N 0.00e+00 13 332
P -6.46e+20 71 104
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.56e+20
Mxy 2.84e+20
Mxz -2.81e+19
Myy 3.84e+20
Myz -3.22e+20
Mzz -5.40e+20
##############
---###################
---##--------###############
######-------------###########
########----------------##########
#########-------------------########
##########--------------------########
###########----------------------#######
###########-----------------------######
############------------------------######
#############----------- ----------#####
#############----------- P ----------#####
##############---------- -----------####
##############-----------------------###
###############----------------------###
## #########----------------------##
# T ###########--------------------#
############------------------#
##############----------------
###############-------------
##############--------
##############
Global CMT Convention Moment Tensor:
R T P
-5.40e+20 -2.81e+19 3.22e+20
-2.81e+19 1.56e+20 -2.84e+20
3.22e+20 -2.84e+20 3.84e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090407102910/index.html
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STK = 160
DIP = 60
RAKE = -75
MW = 3.14
HS = 7.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/07 10:29:10:7 42.33 13.41 9.7 3.1 Italy
Stations used:
IV.FIAM IV.GUAR IV.MNS IV.OFFI
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 6.46e+20 dyne-cm
Mw = 3.14
Z = 7 km
Plane Strike Dip Rake
NP1 160 60 -75
NP2 312 33 -114
Principal Axes:
Axis Value Plunge Azimuth
T 6.46e+20 14 239
N 0.00e+00 13 332
P -6.46e+20 71 104
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.56e+20
Mxy 2.84e+20
Mxz -2.81e+19
Myy 3.84e+20
Myz -3.22e+20
Mzz -5.40e+20
##############
---###################
---##--------###############
######-------------###########
########----------------##########
#########-------------------########
##########--------------------########
###########----------------------#######
###########-----------------------######
############------------------------######
#############----------- ----------#####
#############----------- P ----------#####
##############---------- -----------####
##############-----------------------###
###############----------------------###
## #########----------------------##
# T ###########--------------------#
############------------------#
##############----------------
###############-------------
##############--------
##############
Global CMT Convention Moment Tensor:
R T P
-5.40e+20 -2.81e+19 3.22e+20
-2.81e+19 1.56e+20 -2.84e+20
3.22e+20 -2.84e+20 3.84e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090407102910/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 1.0 225 50 70 3.00 0.4463
WVFGRD96 2.0 225 45 65 3.06 0.4590
WVFGRD96 3.0 10 45 -25 3.02 0.4804
WVFGRD96 4.0 25 55 25 3.05 0.5308
WVFGRD96 5.0 -15 25 -60 3.13 0.5501
WVFGRD96 6.0 330 30 -85 3.14 0.5876
WVFGRD96 7.0 160 60 -75 3.14 0.5990
WVFGRD96 8.0 175 65 -55 3.12 0.5917
WVFGRD96 9.0 180 65 -50 3.13 0.5844
WVFGRD96 10.0 180 65 -50 3.14 0.5720
WVFGRD96 11.0 180 65 -50 3.15 0.5534
WVFGRD96 12.0 185 65 -45 3.16 0.5334
WVFGRD96 13.0 180 60 -50 3.16 0.5076
WVFGRD96 14.0 20 65 35 3.20 0.5084
WVFGRD96 15.0 20 65 35 3.23 0.4929
WVFGRD96 16.0 20 65 35 3.24 0.4872
WVFGRD96 17.0 20 65 35 3.25 0.4804
WVFGRD96 18.0 20 65 35 3.27 0.4735
WVFGRD96 19.0 20 65 35 3.28 0.4642
WVFGRD96 20.0 20 65 35 3.28 0.4516
WVFGRD96 21.0 20 70 35 3.29 0.4392
WVFGRD96 22.0 20 70 35 3.29 0.4256
WVFGRD96 23.0 0 60 -20 3.29 0.4245
WVFGRD96 24.0 0 65 -20 3.30 0.4287
WVFGRD96 25.0 -5 60 -25 3.32 0.4342
WVFGRD96 26.0 355 60 -25 3.34 0.4378
WVFGRD96 27.0 355 65 -20 3.36 0.4372
WVFGRD96 28.0 355 65 -20 3.38 0.4385
WVFGRD96 29.0 -5 65 -20 3.40 0.4357
The best solution is
WVFGRD96 7.0 160 60 -75 3.14 0.5990
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 14:15:02 CDT 2010