2009/04/11 19:53:53 42.347 13.525 9.8 3.00 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/11 19:53:53:0 42.35 13.52 9.8 3.0 Italy
Stations used:
IV.BSSO IV.CERT IV.CESX IV.FAGN IV.FDMO IV.FIAM IV.INTR
IV.LPEL IV.MNS IV.MTCE IV.NRCA 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 = 4.57e+20 dyne-cm
Mw = 3.04
Z = 0 km
Plane Strike Dip Rake
NP1 142 45 -85
NP2 315 45 -95
Principal Axes:
Axis Value Plunge Azimuth
T 4.57e+20 0 229
N 0.00e+00 4 319
P -4.57e+20 86 137
Moment Tensor: (dyne-cm)
Component Value
Mxx 2.00e+20
Mxy 2.28e+20
Mxz 1.99e+19
Myy 2.56e+20
Myz -1.99e+19
Mzz -4.55e+20
##############
######################
-###########################
#-------------################
###-----------------##############
####-------------------#############
#####----------------------###########
######-----------------------###########
######-------------------------#########
#######--------------------------#########
########--------------------------########
#########------------- ----------#######
##########------------ P -----------######
##########----------- -----------#####
###########------------------------#####
###########------------------------###
############----------------------##
# #########-------------------##
T ############----------------
################-----------
######################
##############
Global CMT Convention Moment Tensor:
R T P
-4.55e+20 1.99e+19 1.99e+19
1.99e+19 2.00e+20 -2.28e+20
1.99e+19 -2.28e+20 2.56e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090411195353/index.html
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STK = 315
DIP = 45
RAKE = -95
MW = 3.04
HS = 0.5
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/11 19:53:53:0 42.35 13.52 9.8 3.0 Italy
Stations used:
IV.BSSO IV.CERT IV.CESX IV.FAGN IV.FDMO IV.FIAM IV.INTR
IV.LPEL IV.MNS IV.MTCE IV.NRCA 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 = 4.57e+20 dyne-cm
Mw = 3.04
Z = 0 km
Plane Strike Dip Rake
NP1 142 45 -85
NP2 315 45 -95
Principal Axes:
Axis Value Plunge Azimuth
T 4.57e+20 0 229
N 0.00e+00 4 319
P -4.57e+20 86 137
Moment Tensor: (dyne-cm)
Component Value
Mxx 2.00e+20
Mxy 2.28e+20
Mxz 1.99e+19
Myy 2.56e+20
Myz -1.99e+19
Mzz -4.55e+20
##############
######################
-###########################
#-------------################
###-----------------##############
####-------------------#############
#####----------------------###########
######-----------------------###########
######-------------------------#########
#######--------------------------#########
########--------------------------########
#########------------- ----------#######
##########------------ P -----------######
##########----------- -----------#####
###########------------------------#####
###########------------------------###
############----------------------##
# #########-------------------##
T ############----------------
################-----------
######################
##############
Global CMT Convention Moment Tensor:
R T P
-4.55e+20 1.99e+19 1.99e+19
1.99e+19 2.00e+20 -2.28e+20
1.99e+19 -2.28e+20 2.56e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090411195353/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 0.5 315 45 -95 3.04 0.5073
WVFGRD96 1.0 140 40 -85 3.08 0.4439
WVFGRD96 2.0 320 65 -80 3.16 0.4020
WVFGRD96 3.0 160 35 -60 3.13 0.3408
WVFGRD96 4.0 360 25 -50 3.12 0.3295
WVFGRD96 5.0 0 20 -50 3.21 0.3348
WVFGRD96 6.0 5 25 -50 3.20 0.3169
WVFGRD96 7.0 35 25 -15 3.20 0.3079
WVFGRD96 8.0 295 55 80 3.18 0.3124
WVFGRD96 9.0 300 55 85 3.20 0.3262
WVFGRD96 10.0 295 60 80 3.20 0.3364
WVFGRD96 11.0 295 60 80 3.21 0.3405
WVFGRD96 12.0 300 60 80 3.22 0.3432
WVFGRD96 13.0 305 60 80 3.23 0.3429
WVFGRD96 14.0 305 60 80 3.24 0.3388
WVFGRD96 15.0 305 60 80 3.27 0.3287
WVFGRD96 16.0 300 55 70 3.27 0.3222
WVFGRD96 17.0 300 55 70 3.27 0.3172
WVFGRD96 18.0 300 55 70 3.28 0.3114
WVFGRD96 19.0 300 55 70 3.29 0.3047
WVFGRD96 20.0 300 55 70 3.29 0.2977
WVFGRD96 21.0 305 55 75 3.30 0.2913
WVFGRD96 22.0 305 55 75 3.31 0.2845
WVFGRD96 23.0 310 55 80 3.31 0.2784
WVFGRD96 24.0 140 80 70 3.37 0.2727
WVFGRD96 25.0 140 80 70 3.37 0.2715
WVFGRD96 26.0 145 75 70 3.37 0.2672
WVFGRD96 27.0 325 20 95 3.35 0.2619
WVFGRD96 28.0 145 70 70 3.38 0.2671
WVFGRD96 29.0 140 70 65 3.39 0.2695
The best solution is
WVFGRD96 0.5 315 45 -95 3.04 0.5073
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 08:40:34 CDT 2009