2009/04/09 22:40:06 42.481 13.298 10.9 3.60 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/09 22:40:06:0 42.48 13.30 10.9 3.6 Italy
Stations used:
IV.AOI IV.ARCI IV.ARVD IV.ASSB IV.CAFI IV.CAFR IV.CERT
IV.CESX IV.CING IV.FDMO IV.FIAM IV.GUAR IV.LPEL IV.MGAB
IV.MNS IV.MODR IV.MTCE IV.MURB IV.NRCA IV.OFFI IV.PARC
IV.RMP IV.SGG IV.TERO IV.TOLF IV.TRTR IV.VAGA IV.VVLD
MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 4.62e+21 dyne-cm
Mw = 3.71
Z = 10 km
Plane Strike Dip Rake
NP1 315 85 -80
NP2 71 11 -153
Principal Axes:
Axis Value Plunge Azimuth
T 4.62e+21 39 36
N 0.00e+00 10 134
P -4.62e+21 49 236
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.20e+21
Mxy 3.95e+20
Mxz 3.12e+21
Myy -4.05e+20
Myz 3.22e+21
Mzz -7.91e+20
##############
######################
############################
-#############################
------################# ########
---------############### T #########
------------############# ##########
---------------#########################
-----------------#######################
--------------------#####################-
----------------------###################-
------------------------#################-
--------------------------###############-
---------- -------------#############-
---------- P ---------------##########--
--------- -----------------#######--
-----------------------------#####--
#-----------------------------##--
#---------------------------#-
##----------------------####
###--------------#####
##############
Global CMT Convention Moment Tensor:
R T P
-7.91e+20 3.12e+21 -3.22e+21
3.12e+21 1.20e+21 -3.95e+20
-3.22e+21 -3.95e+20 -4.05e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090409224006/index.html
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STK = 315
DIP = 85
RAKE = -80
MW = 3.71
HS = 10.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/09 22:40:06:0 42.48 13.30 10.9 3.6 Italy
Stations used:
IV.AOI IV.ARCI IV.ARVD IV.ASSB IV.CAFI IV.CAFR IV.CERT
IV.CESX IV.CING IV.FDMO IV.FIAM IV.GUAR IV.LPEL IV.MGAB
IV.MNS IV.MODR IV.MTCE IV.MURB IV.NRCA IV.OFFI IV.PARC
IV.RMP IV.SGG IV.TERO IV.TOLF IV.TRTR IV.VAGA IV.VVLD
MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 4.62e+21 dyne-cm
Mw = 3.71
Z = 10 km
Plane Strike Dip Rake
NP1 315 85 -80
NP2 71 11 -153
Principal Axes:
Axis Value Plunge Azimuth
T 4.62e+21 39 36
N 0.00e+00 10 134
P -4.62e+21 49 236
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.20e+21
Mxy 3.95e+20
Mxz 3.12e+21
Myy -4.05e+20
Myz 3.22e+21
Mzz -7.91e+20
##############
######################
############################
-#############################
------################# ########
---------############### T #########
------------############# ##########
---------------#########################
-----------------#######################
--------------------#####################-
----------------------###################-
------------------------#################-
--------------------------###############-
---------- -------------#############-
---------- P ---------------##########--
--------- -----------------#######--
-----------------------------#####--
#-----------------------------##--
#---------------------------#-
##----------------------####
###--------------#####
##############
Global CMT Convention Moment Tensor:
R T P
-7.91e+20 3.12e+21 -3.22e+21
3.12e+21 1.20e+21 -3.95e+20
-3.22e+21 -3.95e+20 -4.05e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090409224006/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 0.5 130 50 -95 3.52 0.4652
WVFGRD96 1.0 130 50 -90 3.56 0.4083
WVFGRD96 2.0 305 25 -100 3.63 0.3442
WVFGRD96 3.0 135 90 85 3.63 0.4316
WVFGRD96 4.0 315 85 -85 3.60 0.5005
WVFGRD96 5.0 315 85 -85 3.72 0.5563
WVFGRD96 6.0 315 85 -85 3.72 0.6029
WVFGRD96 7.0 135 90 85 3.73 0.6301
WVFGRD96 8.0 315 85 -80 3.69 0.6482
WVFGRD96 9.0 135 90 85 3.70 0.6532
WVFGRD96 10.0 315 85 -80 3.71 0.6534
WVFGRD96 11.0 315 85 -85 3.72 0.6468
WVFGRD96 12.0 315 85 -80 3.73 0.6359
WVFGRD96 13.0 315 85 -85 3.73 0.6223
WVFGRD96 14.0 315 85 -85 3.74 0.6066
WVFGRD96 15.0 135 90 85 3.79 0.5885
WVFGRD96 16.0 315 85 -85 3.80 0.5693
WVFGRD96 17.0 135 90 85 3.80 0.5455
WVFGRD96 18.0 315 85 -85 3.81 0.5252
WVFGRD96 19.0 135 90 80 3.82 0.5005
WVFGRD96 20.0 135 90 80 3.82 0.4776
WVFGRD96 21.0 315 85 -85 3.83 0.4586
WVFGRD96 22.0 315 75 -85 3.84 0.4408
WVFGRD96 23.0 315 70 -85 3.85 0.4280
WVFGRD96 24.0 315 70 -85 3.85 0.4160
WVFGRD96 25.0 290 30 55 3.87 0.4028
WVFGRD96 26.0 305 20 75 3.87 0.3917
WVFGRD96 27.0 300 20 70 3.87 0.3843
WVFGRD96 28.0 310 20 80 3.87 0.3760
WVFGRD96 29.0 140 65 90 3.88 0.3698
The best solution is
WVFGRD96 10.0 315 85 -80 3.71 0.6534
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 Apr 20 11:28:37 CDT 2009