2009/04/15 19:36:44 42.522 13.286 6.3 3.20 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/15 19:36:44:0 42.52 13.29 6.3 3.2 Italy
Stations used:
IV.ARVD IV.ASSB IV.CERT IV.CESX IV.CING IV.FDMO IV.FIAM
IV.GUAR IV.GUMA IV.MNS IV.MTCE IV.NRCA IV.OFFI IV.SACS
IV.TOLF MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 1.64e+21 dyne-cm
Mw = 3.41
Z = 5 km
Plane Strike Dip Rake
NP1 309 72 -99
NP2 155 20 -65
Principal Axes:
Axis Value Plunge Azimuth
T 1.64e+21 26 45
N 0.00e+00 8 311
P -1.64e+21 62 205
Moment Tensor: (dyne-cm)
Component Value
Mxx 3.52e+20
Mxy 5.19e+20
Mxz 1.07e+21
Myy 6.03e+20
Myz 7.57e+20
Mzz -9.56e+20
##############
-#####################
--##########################
-#############################
##---###################### ####
##---------################# T #####
###------------############## ######
###----------------#####################
###-------------------##################
####---------------------#################
####-----------------------###############
####-------------------------#############
####---------------------------###########
####----------- -------------#########
####----------- P ---------------#######
####---------- ----------------#####
####-----------------------------###
#####----------------------------#
#####-------------------------
######----------------------
######----------------
#########---##
Global CMT Convention Moment Tensor:
R T P
-9.56e+20 1.07e+21 -7.57e+20
1.07e+21 3.52e+20 -5.19e+20
-7.57e+20 -5.19e+20 6.03e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090415193644/index.html
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STK = 155
DIP = 20
RAKE = -65
MW = 3.41
HS = 5.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/15 19:36:44:0 42.52 13.29 6.3 3.2 Italy
Stations used:
IV.ARVD IV.ASSB IV.CERT IV.CESX IV.CING IV.FDMO IV.FIAM
IV.GUAR IV.GUMA IV.MNS IV.MTCE IV.NRCA IV.OFFI IV.SACS
IV.TOLF MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 1.64e+21 dyne-cm
Mw = 3.41
Z = 5 km
Plane Strike Dip Rake
NP1 309 72 -99
NP2 155 20 -65
Principal Axes:
Axis Value Plunge Azimuth
T 1.64e+21 26 45
N 0.00e+00 8 311
P -1.64e+21 62 205
Moment Tensor: (dyne-cm)
Component Value
Mxx 3.52e+20
Mxy 5.19e+20
Mxz 1.07e+21
Myy 6.03e+20
Myz 7.57e+20
Mzz -9.56e+20
##############
-#####################
--##########################
-#############################
##---###################### ####
##---------################# T #####
###------------############## ######
###----------------#####################
###-------------------##################
####---------------------#################
####-----------------------###############
####-------------------------#############
####---------------------------###########
####----------- -------------#########
####----------- P ---------------#######
####---------- ----------------#####
####-----------------------------###
#####----------------------------#
#####-------------------------
######----------------------
######----------------
#########---##
Global CMT Convention Moment Tensor:
R T P
-9.56e+20 1.07e+21 -7.57e+20
1.07e+21 3.52e+20 -5.19e+20
-7.57e+20 -5.19e+20 6.03e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090415193644/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 0.5 320 40 -80 3.15 0.4124
WVFGRD96 1.0 320 40 -80 3.19 0.3542
WVFGRD96 2.0 160 15 -50 3.33 0.4098
WVFGRD96 3.0 165 20 -50 3.31 0.5005
WVFGRD96 4.0 155 20 -65 3.31 0.5439
WVFGRD96 5.0 155 20 -65 3.41 0.5739
WVFGRD96 6.0 155 25 -65 3.41 0.5737
WVFGRD96 7.0 155 25 -65 3.40 0.5616
WVFGRD96 8.0 160 25 -60 3.35 0.5358
WVFGRD96 9.0 170 30 -45 3.35 0.5177
WVFGRD96 10.0 175 30 -40 3.35 0.4980
WVFGRD96 11.0 180 30 -30 3.35 0.4773
WVFGRD96 12.0 180 30 -30 3.35 0.4568
WVFGRD96 13.0 175 30 -35 3.36 0.4361
WVFGRD96 14.0 180 30 -30 3.36 0.4161
WVFGRD96 15.0 180 30 -25 3.40 0.4001
WVFGRD96 16.0 180 30 -25 3.41 0.3806
WVFGRD96 17.0 180 30 -25 3.41 0.3625
WVFGRD96 18.0 180 35 -20 3.42 0.3470
WVFGRD96 19.0 180 35 -20 3.43 0.3323
WVFGRD96 20.0 180 35 -20 3.43 0.3185
WVFGRD96 21.0 175 40 -25 3.44 0.3058
WVFGRD96 22.0 170 40 -30 3.45 0.2981
WVFGRD96 23.0 170 40 -30 3.46 0.2925
WVFGRD96 24.0 170 40 -35 3.47 0.2888
WVFGRD96 25.0 170 40 -35 3.48 0.2876
WVFGRD96 26.0 170 40 -35 3.49 0.2868
WVFGRD96 27.0 165 40 -40 3.50 0.2862
WVFGRD96 28.0 165 40 -40 3.50 0.2850
WVFGRD96 29.0 120 80 60 3.49 0.2840
The best solution is
WVFGRD96 5.0 155 20 -65 3.41 0.5739
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=Wed Apr 29 11:23:15 CDT 2009