2009/04/11 06:13:26 42.469 13.417 9.1 3.00 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/11 06:13:26:0 42.47 13.42 9.1 3.0 Italy
Stations used:
IV.ARVD IV.CERT IV.CESX IV.FAGN IV.FDMO IV.OFFI IV.TERO
MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 7.67e+20 dyne-cm
Mw = 3.19
Z = 5 km
Plane Strike Dip Rake
NP1 145 55 -90
NP2 325 35 -90
Principal Axes:
Axis Value Plunge Azimuth
T 7.67e+20 10 235
N 0.00e+00 -0 325
P -7.67e+20 80 55
Moment Tensor: (dyne-cm)
Component Value
Mxx 2.37e+20
Mxy 3.39e+20
Mxz -1.51e+20
Myy 4.84e+20
Myz -2.15e+20
Mzz -7.21e+20
##############
##----################
##--------------############
##------------------##########
####--------------------##########
#####----------------------#########
######------------------------########
########------------------------########
########-------------------------#######
##########----------- -----------#######
##########----------- P -----------#######
###########---------- ------------######
############------------------------######
############-----------------------#####
##############---------------------#####
## #########--------------------####
# T ###########------------------###
#############---------------###
#################------------#
####################-------#
######################
##############
Global CMT Convention Moment Tensor:
R T P
-7.21e+20 -1.51e+20 2.15e+20
-1.51e+20 2.37e+20 -3.39e+20
2.15e+20 -3.39e+20 4.84e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090411061326/index.html
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STK = 145
DIP = 55
RAKE = -90
MW = 3.19
HS = 5.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/11 06:13:26:0 42.47 13.42 9.1 3.0 Italy
Stations used:
IV.ARVD IV.CERT IV.CESX IV.FAGN IV.FDMO IV.OFFI IV.TERO
MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 7.67e+20 dyne-cm
Mw = 3.19
Z = 5 km
Plane Strike Dip Rake
NP1 145 55 -90
NP2 325 35 -90
Principal Axes:
Axis Value Plunge Azimuth
T 7.67e+20 10 235
N 0.00e+00 -0 325
P -7.67e+20 80 55
Moment Tensor: (dyne-cm)
Component Value
Mxx 2.37e+20
Mxy 3.39e+20
Mxz -1.51e+20
Myy 4.84e+20
Myz -2.15e+20
Mzz -7.21e+20
##############
##----################
##--------------############
##------------------##########
####--------------------##########
#####----------------------#########
######------------------------########
########------------------------########
########-------------------------#######
##########----------- -----------#######
##########----------- P -----------#######
###########---------- ------------######
############------------------------######
############-----------------------#####
##############---------------------#####
## #########--------------------####
# T ###########------------------###
#############---------------###
#################------------#
####################-------#
######################
##############
Global CMT Convention Moment Tensor:
R T P
-7.21e+20 -1.51e+20 2.15e+20
-1.51e+20 2.37e+20 -3.39e+20
2.15e+20 -3.39e+20 4.84e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090411061326/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 0.5 350 30 -55 2.95 0.3707
WVFGRD96 1.0 350 45 -55 2.92 0.3733
WVFGRD96 2.0 350 30 -50 3.03 0.4311
WVFGRD96 3.0 145 60 -95 3.08 0.4834
WVFGRD96 4.0 325 35 -90 3.11 0.5119
WVFGRD96 5.0 145 55 -90 3.19 0.5347
WVFGRD96 6.0 150 55 -85 3.19 0.4984
WVFGRD96 7.0 160 60 -70 3.19 0.4479
WVFGRD96 8.0 160 60 -70 3.15 0.3937
WVFGRD96 9.0 165 65 -65 3.15 0.3629
WVFGRD96 10.0 10 70 15 3.08 0.3406
WVFGRD96 11.0 220 65 20 3.10 0.3354
WVFGRD96 12.0 220 60 20 3.11 0.3305
WVFGRD96 13.0 220 60 20 3.12 0.3251
WVFGRD96 14.0 220 65 25 3.13 0.3199
WVFGRD96 15.0 225 60 25 3.16 0.3108
WVFGRD96 16.0 225 60 25 3.16 0.3065
WVFGRD96 17.0 225 65 30 3.18 0.3026
WVFGRD96 18.0 225 65 30 3.18 0.2999
WVFGRD96 19.0 215 50 0 3.18 0.2981
WVFGRD96 20.0 215 50 0 3.19 0.2980
WVFGRD96 21.0 215 45 -5 3.21 0.2982
WVFGRD96 22.0 215 45 0 3.21 0.2978
WVFGRD96 23.0 220 50 5 3.23 0.2962
WVFGRD96 24.0 220 50 5 3.24 0.2941
WVFGRD96 25.0 225 50 10 3.25 0.2921
WVFGRD96 26.0 225 50 15 3.25 0.2923
WVFGRD96 27.0 225 55 20 3.25 0.2925
WVFGRD96 28.0 225 55 20 3.27 0.2938
WVFGRD96 29.0 300 25 40 3.31 0.2922
The best solution is
WVFGRD96 5.0 145 55 -90 3.19 0.5347
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 08:18:10 CDT 2009