2009/04/06 01:32:39 42.334 13.334 8.8 5.80 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/06 01:32:39:0 42.33 13.33 8.8 5.8 Italy
Stations used:
IV.AOI IV.ARCI IV.ARVD IV.CERT IV.FDMO IV.FSSB IV.MGAB
IV.RMP IV.SACS
Filtering commands used:
hp c 0.01 n 3
lp c 0.03 n 3
Best Fitting Double Couple
Mo = 3.20e+25 dyne-cm
Mw = 6.27
Z = 5 km
Plane Strike Dip Rake
NP1 315 60 -85
NP2 125 30 -99
Principal Axes:
Axis Value Plunge Azimuth
T 3.20e+25 15 41
N 0.00e+00 4 132
P -3.20e+25 74 238
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.62e+25
Mxy 1.38e+25
Mxz 1.03e+25
Myy 1.14e+25
Myz 1.23e+25
Mzz -2.76e+25
##############
######################
######################## #
-------################## T ##
-------------############## ####
#-----------------##################
#--------------------#################
##----------------------################
##------------------------##############
###--------------------------#############
####--------------------------############
####----------- -------------###########
#####---------- P ---------------#########
#####--------- ----------------#######
######---------------------------#######
#######--------------------------#####
#######-------------------------####
#########-----------------------##
##########-------------------#
##############---------#####
######################
##############
Global CMT Convention Moment Tensor:
R T P
-2.76e+25 1.03e+25 -1.23e+25
1.03e+25 1.62e+25 -1.38e+25
-1.23e+25 -1.38e+25 1.14e+25
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090406013239/index.html
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STK = 315
DIP = 60
RAKE = -85
MW = 6.27
HS = 5.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/06 01:32:39:0 42.33 13.33 8.8 5.8 Italy
Stations used:
IV.AOI IV.ARCI IV.ARVD IV.CERT IV.FDMO IV.FSSB IV.MGAB
IV.RMP IV.SACS
Filtering commands used:
hp c 0.01 n 3
lp c 0.03 n 3
Best Fitting Double Couple
Mo = 3.20e+25 dyne-cm
Mw = 6.27
Z = 5 km
Plane Strike Dip Rake
NP1 315 60 -85
NP2 125 30 -99
Principal Axes:
Axis Value Plunge Azimuth
T 3.20e+25 15 41
N 0.00e+00 4 132
P -3.20e+25 74 238
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.62e+25
Mxy 1.38e+25
Mxz 1.03e+25
Myy 1.14e+25
Myz 1.23e+25
Mzz -2.76e+25
##############
######################
######################## #
-------################## T ##
-------------############## ####
#-----------------##################
#--------------------#################
##----------------------################
##------------------------##############
###--------------------------#############
####--------------------------############
####----------- -------------###########
#####---------- P ---------------#########
#####--------- ----------------#######
######---------------------------#######
#######--------------------------#####
#######-------------------------####
#########-----------------------##
##########-------------------#
##############---------#####
######################
##############
Global CMT Convention Moment Tensor:
R T P
-2.76e+25 1.03e+25 -1.23e+25
1.03e+25 1.62e+25 -1.38e+25
-1.23e+25 -1.38e+25 1.14e+25
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090406013239/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 0.01 n 3 lp c 0.03 n 3The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT
WVFGRD96 0.5 160 10 -35 6.46 0.5713
WVFGRD96 1.0 155 15 -50 6.33 0.5958
WVFGRD96 2.0 150 20 -60 6.28 0.6317
WVFGRD96 3.0 130 25 -100 6.25 0.6725
WVFGRD96 4.0 135 30 -90 6.25 0.6950
WVFGRD96 5.0 135 30 -90 6.26 0.7031
WVFGRD96 6.0 320 55 -85 6.26 0.7032
WVFGRD96 7.0 320 50 -80 6.25 0.6927
WVFGRD96 8.0 325 50 -75 6.25 0.6636
WVFGRD96 9.0 135 40 -90 6.24 0.6443
WVFGRD96 10.0 145 40 -75 6.23 0.6301
WVFGRD96 11.0 320 75 -75 6.22 0.6271
WVFGRD96 12.0 325 80 -65 6.22 0.6294
WVFGRD96 13.0 325 80 -65 6.21 0.6338
WVFGRD96 14.0 325 80 -65 6.21 0.6377
WVFGRD96 15.0 325 80 -70 6.24 0.6475
WVFGRD96 16.0 325 80 -70 6.24 0.6528
WVFGRD96 17.0 325 85 -65 6.24 0.6590
WVFGRD96 18.0 325 85 -65 6.24 0.6656
WVFGRD96 19.0 325 85 -65 6.24 0.6716
WVFGRD96 20.0 325 85 -65 6.24 0.6769
WVFGRD96 21.0 325 85 -65 6.24 0.6813
WVFGRD96 22.0 150 90 60 6.24 0.6837
WVFGRD96 23.0 325 85 -65 6.24 0.6874
WVFGRD96 24.0 330 90 -60 6.24 0.6893
WVFGRD96 25.0 330 90 -60 6.24 0.6912
WVFGRD96 26.0 330 90 -55 6.25 0.6925
WVFGRD96 27.0 330 90 -55 6.25 0.6930
WVFGRD96 28.0 330 90 -55 6.25 0.6926
WVFGRD96 29.0 155 80 45 6.26 0.6940
The best solution is
WVFGRD96 6.0 320 55 -85 6.26 0.7032
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 0.01 n 3 lp c 0.03 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=Tue Apr 21 08:27:47 CDT 2009