2009/04/08 13:02:28 42.502 13.367 9.7 3.1 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/08 13:02:28:3 42.50 13.37 9.7 3.1 Italy
Stations used:
IV.ARVD IV.CESI IV.NRCA IV.OFFI MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 4.42e+20 dyne-cm
Mw = 3.03
Z = 6 km
Plane Strike Dip Rake
NP1 135 65 -90
NP2 315 25 -90
Principal Axes:
Axis Value Plunge Azimuth
T 4.42e+20 20 225
N 0.00e+00 -0 135
P -4.42e+20 70 45
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.69e+20
Mxy 1.69e+20
Mxz -2.01e+20
Myy 1.69e+20
Myz -2.01e+20
Mzz -3.38e+20
##############
#####---##############
#------------------#########
-----------------------#######
###------------------------#######
####--------------------------######
######---------------------------#####
########--------------- ---------#####
########--------------- P ----------####
###########------------- ----------#####
############--------------------------####
#############-------------------------####
###############------------------------###
################----------------------##
##################--------------------##
###################-----------------##
##### ############---------------#
#### T ################----------#
## ####################-----
############################
######################
##############
Global CMT Convention Moment Tensor:
R T P
-3.38e+20 -2.01e+20 2.01e+20
-2.01e+20 1.69e+20 -1.69e+20
2.01e+20 -1.69e+20 1.69e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090408130228/index.html
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STK = 315
DIP = 25
RAKE = -90
MW = 3.03
HS = 6.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/08 13:02:28:3 42.50 13.37 9.7 3.1 Italy
Stations used:
IV.ARVD IV.CESI IV.NRCA IV.OFFI MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 4.42e+20 dyne-cm
Mw = 3.03
Z = 6 km
Plane Strike Dip Rake
NP1 135 65 -90
NP2 315 25 -90
Principal Axes:
Axis Value Plunge Azimuth
T 4.42e+20 20 225
N 0.00e+00 -0 135
P -4.42e+20 70 45
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.69e+20
Mxy 1.69e+20
Mxz -2.01e+20
Myy 1.69e+20
Myz -2.01e+20
Mzz -3.38e+20
##############
#####---##############
#------------------#########
-----------------------#######
###------------------------#######
####--------------------------######
######---------------------------#####
########--------------- ---------#####
########--------------- P ----------####
###########------------- ----------#####
############--------------------------####
#############-------------------------####
###############------------------------###
################----------------------##
##################--------------------##
###################-----------------##
##### ############---------------#
#### T ################----------#
## ####################-----
############################
######################
##############
Global CMT Convention Moment Tensor:
R T P
-3.38e+20 -2.01e+20 2.01e+20
-2.01e+20 1.69e+20 -1.69e+20
2.01e+20 -1.69e+20 1.69e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090408130228/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 1.0 305 50 -65 2.73 0.3128
WVFGRD96 2.0 345 20 -50 2.90 0.3425
WVFGRD96 3.0 340 20 -60 2.90 0.4228
WVFGRD96 4.0 325 25 -80 2.93 0.4641
WVFGRD96 5.0 135 65 -95 3.03 0.5066
WVFGRD96 6.0 315 25 -90 3.03 0.5149
WVFGRD96 7.0 135 60 -90 3.03 0.4993
WVFGRD96 8.0 320 35 -85 2.97 0.4607
WVFGRD96 9.0 320 35 -90 2.98 0.4353
WVFGRD96 10.0 5 65 35 3.00 0.4203
WVFGRD96 11.0 5 65 30 3.00 0.4224
WVFGRD96 12.0 5 65 30 3.02 0.4240
WVFGRD96 13.0 5 65 30 3.04 0.4238
WVFGRD96 14.0 5 65 30 3.06 0.4254
WVFGRD96 15.0 5 65 25 3.07 0.4213
WVFGRD96 16.0 5 65 25 3.09 0.4181
WVFGRD96 17.0 5 65 25 3.10 0.4131
WVFGRD96 18.0 5 65 25 3.12 0.4080
WVFGRD96 19.0 5 65 20 3.11 0.4029
WVFGRD96 20.0 145 40 -80 3.11 0.3974
WVFGRD96 21.0 165 30 -75 3.14 0.3957
WVFGRD96 22.0 160 30 -75 3.14 0.4091
WVFGRD96 23.0 160 30 -75 3.14 0.4173
WVFGRD96 24.0 160 30 -75 3.15 0.4230
WVFGRD96 25.0 165 30 -70 3.15 0.4241
WVFGRD96 26.0 165 30 -70 3.15 0.4209
WVFGRD96 27.0 170 30 -70 3.16 0.4159
WVFGRD96 28.0 170 30 -70 3.16 0.4100
WVFGRD96 29.0 185 35 -60 3.19 0.4053
The best solution is
WVFGRD96 6.0 315 25 -90 3.03 0.5149
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 13:57:32 CDT 2010