2009/04/16 17:49:30 42.5400 13.2890 10.9 3.80 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/16 17:49:30:0 42.54 13.29 10.9 3.8 Italy
Stations used:
IV.ASSB IV.CERT IV.CESX IV.CING IV.FDMO IV.FIAM IV.GUMA
IV.LPEL IV.MNS IV.MTCE IV.OFFI IV.RMP IV.TERO MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 5.50e+21 dyne-cm
Mw = 3.76
Z = 7 km
Plane Strike Dip Rake
NP1 322 62 -101
NP2 165 30 -70
Principal Axes:
Axis Value Plunge Azimuth
T 5.50e+21 16 60
N 0.00e+00 10 327
P -5.50e+21 71 208
Moment Tensor: (dyne-cm)
Component Value
Mxx 7.69e+20
Mxy 1.93e+21
Mxz 2.24e+21
Myy 3.70e+21
Myz 2.07e+21
Mzz -4.47e+21
-#############
--####################
####-#######################
###-------####################
####-----------###################
####--------------############## #
#####----------------############ T ##
#####-------------------########## ###
#####--------------------###############
######----------------------##############
######-----------------------#############
######------------------------############
#######---------- -----------###########
######---------- P ------------#########
#######--------- -------------########
#######------------------------#######
#######------------------------#####
#######-----------------------####
#######---------------------##
########-------------------#
#######---------------
########------
Global CMT Convention Moment Tensor:
R T P
-4.47e+21 2.24e+21 -2.07e+21
2.24e+21 7.69e+20 -1.93e+21
-2.07e+21 -1.93e+21 3.70e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090416174930/index.html
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STK = 165
DIP = 30
RAKE = -70
MW = 3.76
HS = 7.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/16 17:49:30:0 42.54 13.29 10.9 3.8 Italy
Stations used:
IV.ASSB IV.CERT IV.CESX IV.CING IV.FDMO IV.FIAM IV.GUMA
IV.LPEL IV.MNS IV.MTCE IV.OFFI IV.RMP IV.TERO MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 5.50e+21 dyne-cm
Mw = 3.76
Z = 7 km
Plane Strike Dip Rake
NP1 322 62 -101
NP2 165 30 -70
Principal Axes:
Axis Value Plunge Azimuth
T 5.50e+21 16 60
N 0.00e+00 10 327
P -5.50e+21 71 208
Moment Tensor: (dyne-cm)
Component Value
Mxx 7.69e+20
Mxy 1.93e+21
Mxz 2.24e+21
Myy 3.70e+21
Myz 2.07e+21
Mzz -4.47e+21
-#############
--####################
####-#######################
###-------####################
####-----------###################
####--------------############## #
#####----------------############ T ##
#####-------------------########## ###
#####--------------------###############
######----------------------##############
######-----------------------#############
######------------------------############
#######---------- -----------###########
######---------- P ------------#########
#######--------- -------------########
#######------------------------#######
#######------------------------#####
#######-----------------------####
#######---------------------##
########-------------------#
#######---------------
########------
Global CMT Convention Moment Tensor:
R T P
-4.47e+21 2.24e+21 -2.07e+21
2.24e+21 7.69e+20 -1.93e+21
-2.07e+21 -1.93e+21 3.70e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090416174930/index.html
|
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 0.5 350 55 -65 3.49 0.3305
WVFGRD96 1.0 345 50 -70 3.52 0.3070
WVFGRD96 2.0 195 25 -15 3.64 0.3435
WVFGRD96 3.0 195 30 -20 3.63 0.4152
WVFGRD96 4.0 190 35 -35 3.64 0.4576
WVFGRD96 5.0 180 30 -45 3.74 0.4956
WVFGRD96 6.0 160 30 -75 3.77 0.5197
WVFGRD96 7.0 165 30 -70 3.76 0.5234
WVFGRD96 8.0 165 35 -70 3.73 0.5068
WVFGRD96 9.0 170 35 -65 3.73 0.4917
WVFGRD96 10.0 180 40 -45 3.73 0.4770
WVFGRD96 11.0 180 40 -45 3.73 0.4590
WVFGRD96 12.0 185 45 -35 3.74 0.4411
WVFGRD96 13.0 190 45 -30 3.74 0.4219
WVFGRD96 14.0 190 45 -30 3.75 0.4019
WVFGRD96 15.0 190 45 -30 3.78 0.3889
WVFGRD96 16.0 180 50 -45 3.79 0.3738
WVFGRD96 17.0 180 50 -45 3.80 0.3631
WVFGRD96 18.0 180 50 -45 3.81 0.3538
WVFGRD96 19.0 180 55 -40 3.81 0.3471
WVFGRD96 20.0 180 55 -40 3.82 0.3416
WVFGRD96 21.0 185 55 -35 3.83 0.3356
WVFGRD96 22.0 185 55 -35 3.83 0.3303
WVFGRD96 23.0 185 55 -35 3.84 0.3254
WVFGRD96 24.0 180 50 -45 3.85 0.3199
WVFGRD96 25.0 180 50 -50 3.86 0.3175
WVFGRD96 26.0 180 50 -50 3.87 0.3128
WVFGRD96 27.0 10 45 -40 3.86 0.3096
WVFGRD96 28.0 10 45 -45 3.87 0.3116
WVFGRD96 29.0 10 45 -45 3.89 0.3121
The best solution is
WVFGRD96 7.0 165 30 -70 3.76 0.5234
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=Fri Apr 17 10:17:17 CDT 2009