2009/04/18 11:07:21 42.265 13.494 9.4 3.20 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/18 11:07:21:0 42.26 13.49 9.4 3.2 Italy
Stations used:
IV.AOI IV.CAFR IV.CERA IV.CERT IV.CING IV.FDMO IV.FIAM
IV.GUAR IV.GUMA IV.INTR IV.LPEL IV.MIDA IV.MNS IV.MTCE
IV.OFFI IV.PTRJ IV.RDP IV.RMP IV.SGG IV.TERO IV.TOLF
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 = 2.48e+21 dyne-cm
Mw = 3.53
Z = 6 km
Plane Strike Dip Rake
NP1 150 65 -75
NP2 298 29 -119
Principal Axes:
Axis Value Plunge Azimuth
T 2.48e+21 19 229
N 0.00e+00 14 324
P -2.48e+21 67 87
Moment Tensor: (dyne-cm)
Component Value
Mxx 9.64e+20
Mxy 1.09e+21
Mxz -5.36e+20
Myy 8.74e+20
Myz -1.47e+21
Mzz -1.84e+21
##############
-#####################
---#####-----###############
--##-----------------#########
-#####--------------------########
########---------------------#######
#########-----------------------######
##########-------------------------#####
###########-------------------------####
#############------------- ---------####
#############------------- P ----------###
##############------------ ----------###
###############-------------------------##
###############------------------------#
#################----------------------#
#################---------------------
#### ##########-------------------
### T ############----------------
# ##############------------
####################--------
####################--
##############
Global CMT Convention Moment Tensor:
R T P
-1.84e+21 -5.36e+20 1.47e+21
-5.36e+20 9.64e+20 -1.09e+21
1.47e+21 -1.09e+21 8.74e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090418110721/index.html
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STK = 150
DIP = 65
RAKE = -75
MW = 3.53
HS = 6.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/18 11:07:21:0 42.26 13.49 9.4 3.2 Italy
Stations used:
IV.AOI IV.CAFR IV.CERA IV.CERT IV.CING IV.FDMO IV.FIAM
IV.GUAR IV.GUMA IV.INTR IV.LPEL IV.MIDA IV.MNS IV.MTCE
IV.OFFI IV.PTRJ IV.RDP IV.RMP IV.SGG IV.TERO IV.TOLF
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 = 2.48e+21 dyne-cm
Mw = 3.53
Z = 6 km
Plane Strike Dip Rake
NP1 150 65 -75
NP2 298 29 -119
Principal Axes:
Axis Value Plunge Azimuth
T 2.48e+21 19 229
N 0.00e+00 14 324
P -2.48e+21 67 87
Moment Tensor: (dyne-cm)
Component Value
Mxx 9.64e+20
Mxy 1.09e+21
Mxz -5.36e+20
Myy 8.74e+20
Myz -1.47e+21
Mzz -1.84e+21
##############
-#####################
---#####-----###############
--##-----------------#########
-#####--------------------########
########---------------------#######
#########-----------------------######
##########-------------------------#####
###########-------------------------####
#############------------- ---------####
#############------------- P ----------###
##############------------ ----------###
###############-------------------------##
###############------------------------#
#################----------------------#
#################---------------------
#### ##########-------------------
### T ############----------------
# ##############------------
####################--------
####################--
##############
Global CMT Convention Moment Tensor:
R T P
-1.84e+21 -5.36e+20 1.47e+21
-5.36e+20 9.64e+20 -1.09e+21
1.47e+21 -1.09e+21 8.74e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090418110721/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 0.5 165 65 -55 3.26 0.3540
WVFGRD96 1.0 160 60 -60 3.29 0.3608
WVFGRD96 2.0 170 85 -65 3.39 0.3813
WVFGRD96 3.0 160 75 -70 3.41 0.4421
WVFGRD96 4.0 155 70 -70 3.42 0.4792
WVFGRD96 5.0 155 70 -75 3.52 0.5167
WVFGRD96 6.0 150 65 -75 3.53 0.5298
WVFGRD96 7.0 155 65 -70 3.52 0.5199
WVFGRD96 8.0 155 65 -65 3.47 0.4971
WVFGRD96 9.0 160 65 -60 3.47 0.4866
WVFGRD96 10.0 165 70 -55 3.47 0.4770
WVFGRD96 11.0 170 75 -45 3.48 0.4672
WVFGRD96 12.0 170 75 -45 3.49 0.4568
WVFGRD96 13.0 175 80 -40 3.50 0.4445
WVFGRD96 14.0 0 90 35 3.52 0.4305
WVFGRD96 15.0 170 75 -45 3.54 0.4217
WVFGRD96 16.0 175 80 -40 3.55 0.4084
WVFGRD96 17.0 175 80 -40 3.56 0.3952
WVFGRD96 18.0 175 75 -40 3.57 0.3827
WVFGRD96 19.0 175 75 -40 3.58 0.3716
WVFGRD96 20.0 175 75 -35 3.58 0.3615
WVFGRD96 21.0 175 75 -35 3.59 0.3523
WVFGRD96 22.0 175 75 -30 3.59 0.3434
WVFGRD96 23.0 185 60 15 3.59 0.3402
WVFGRD96 24.0 185 60 20 3.60 0.3354
WVFGRD96 25.0 185 60 20 3.60 0.3313
WVFGRD96 26.0 185 60 20 3.61 0.3278
WVFGRD96 27.0 185 60 20 3.62 0.3251
WVFGRD96 28.0 185 60 20 3.63 0.3222
WVFGRD96 29.0 185 60 20 3.65 0.3211
The best solution is
WVFGRD96 6.0 150 65 -75 3.53 0.5298
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=Thu Apr 30 15:52:54 CDT 2009