2009/04/08 21:11:04 42.297 13.570 10.1 3.10 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/08 21:11:04:0 42.30 13.57 10.1 3.1 Italy
Stations used:
IV.CESX IV.CING IV.FDMO IV.FIAM IV.INTR IV.MODR IV.MTCE
IV.NRCA IV.OFFI IV.TERO IV.TOLF MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 4.27e+20 dyne-cm
Mw = 3.02
Z = 0 km
Plane Strike Dip Rake
NP1 155 50 -75
NP2 312 42 -107
Principal Axes:
Axis Value Plunge Azimuth
T 4.27e+20 4 234
N 0.00e+00 11 325
P -4.27e+20 78 126
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.37e+20
Mxy 2.10e+20
Mxz 3.41e+19
Myy 2.69e+20
Myz -9.48e+19
Mzz -4.06e+20
##############
-#####################
----########################
####-----------###############
#####----------------#############
######------------------############
#######--------------------###########
########----------------------##########
########------------------------########
##########------------------------########
##########-------------------------#######
###########------------ ----------######
###########------------ P ----------######
###########----------- -----------####
############------------------------####
############-----------------------###
##########---------------------##
T ###########--------------------#
#############-----------------
##############--------------
###############-------
##############
Global CMT Convention Moment Tensor:
R T P
-4.06e+20 3.41e+19 9.48e+19
3.41e+19 1.37e+20 -2.10e+20
9.48e+19 -2.10e+20 2.69e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090408211104/index.html
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STK = 155
DIP = 50
RAKE = -75
MW = 3.02
HS = 0.5
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/08 21:11:04:0 42.30 13.57 10.1 3.1 Italy
Stations used:
IV.CESX IV.CING IV.FDMO IV.FIAM IV.INTR IV.MODR IV.MTCE
IV.NRCA IV.OFFI IV.TERO IV.TOLF MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 4.27e+20 dyne-cm
Mw = 3.02
Z = 0 km
Plane Strike Dip Rake
NP1 155 50 -75
NP2 312 42 -107
Principal Axes:
Axis Value Plunge Azimuth
T 4.27e+20 4 234
N 0.00e+00 11 325
P -4.27e+20 78 126
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.37e+20
Mxy 2.10e+20
Mxz 3.41e+19
Myy 2.69e+20
Myz -9.48e+19
Mzz -4.06e+20
##############
-#####################
----########################
####-----------###############
#####----------------#############
######------------------############
#######--------------------###########
########----------------------##########
########------------------------########
##########------------------------########
##########-------------------------#######
###########------------ ----------######
###########------------ P ----------######
###########----------- -----------####
############------------------------####
############-----------------------###
##########---------------------##
T ###########--------------------#
#############-----------------
##############--------------
###############-------
##############
Global CMT Convention Moment Tensor:
R T P
-4.06e+20 3.41e+19 9.48e+19
3.41e+19 1.37e+20 -2.10e+20
9.48e+19 -2.10e+20 2.69e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090408211104/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 0.5 155 50 -75 3.02 0.4859
WVFGRD96 1.0 325 45 -90 3.06 0.4659
WVFGRD96 2.0 340 45 -65 3.10 0.4339
WVFGRD96 3.0 330 25 -90 3.14 0.4065
WVFGRD96 4.0 330 30 -90 3.14 0.3874
WVFGRD96 5.0 150 60 -90 3.22 0.3928
WVFGRD96 6.0 335 30 -85 3.21 0.3604
WVFGRD96 7.0 -5 30 -60 3.19 0.3311
WVFGRD96 8.0 25 60 20 3.14 0.3314
WVFGRD96 9.0 25 60 20 3.16 0.3292
WVFGRD96 10.0 25 60 20 3.17 0.3254
WVFGRD96 11.0 20 60 25 3.17 0.3227
WVFGRD96 12.0 25 55 30 3.18 0.3191
WVFGRD96 13.0 190 65 35 3.18 0.3200
WVFGRD96 14.0 190 65 35 3.19 0.3174
WVFGRD96 15.0 190 60 35 3.22 0.3130
WVFGRD96 16.0 190 60 35 3.23 0.3072
WVFGRD96 17.0 190 65 35 3.24 0.3010
WVFGRD96 18.0 185 65 30 3.25 0.2950
WVFGRD96 19.0 185 65 30 3.26 0.2910
WVFGRD96 20.0 185 65 30 3.27 0.2878
WVFGRD96 21.0 185 65 30 3.28 0.2841
WVFGRD96 22.0 185 65 30 3.29 0.2789
WVFGRD96 23.0 185 60 25 3.29 0.2728
WVFGRD96 24.0 185 60 25 3.29 0.2672
WVFGRD96 25.0 185 60 25 3.30 0.2607
WVFGRD96 26.0 195 65 35 3.30 0.2579
WVFGRD96 27.0 195 65 35 3.31 0.2585
WVFGRD96 28.0 195 65 35 3.33 0.2585
WVFGRD96 29.0 195 65 35 3.34 0.2595
The best solution is
WVFGRD96 0.5 155 50 -75 3.02 0.4859
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 May 1 08:11:04 CDT 2009