2009/04/12 18:05:16 42.395 13.394 9.8 3.40 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/12 18:05:16:0 42.40 13.39 9.8 3.4 Italy
Stations used:
IV.CERT IV.CESX IV.FAGN IV.FDMO IV.FIAM IV.MNS IV.MTCE
IV.NRCA IV.OFFI IV.TERO
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 8.22e+20 dyne-cm
Mw = 3.21
Z = 2 km
Plane Strike Dip Rake
NP1 135 50 -85
NP2 307 40 -96
Principal Axes:
Axis Value Plunge Azimuth
T 8.22e+20 5 221
N 0.00e+00 4 312
P -8.22e+20 84 80
Moment Tensor: (dyne-cm)
Component Value
Mxx 4.58e+20
Mxy 4.03e+20
Mxz -6.80e+19
Myy 3.48e+20
Myz -1.33e+20
Mzz -8.07e+20
##############
######################
############################
#--------------###############
##-------------------#############
###----------------------###########
####------------------------##########
#####--------------------------#########
######---------------------------#######
#######---------------- ---------#######
########--------------- P ----------######
#########-------------- -----------#####
##########---------------------------#####
###########--------------------------###
############-------------------------###
#############-----------------------##
##############---------------------#
################------------------
# ##############------------
T #########################
######################
##############
Global CMT Convention Moment Tensor:
R T P
-8.07e+20 -6.80e+19 1.33e+20
-6.80e+19 4.58e+20 -4.03e+20
1.33e+20 -4.03e+20 3.48e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090412180516/index.html
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STK = 135
DIP = 50
RAKE = -85
MW = 3.21
HS = 2.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/12 18:05:16:0 42.40 13.39 9.8 3.4 Italy
Stations used:
IV.CERT IV.CESX IV.FAGN IV.FDMO IV.FIAM IV.MNS IV.MTCE
IV.NRCA IV.OFFI IV.TERO
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 8.22e+20 dyne-cm
Mw = 3.21
Z = 2 km
Plane Strike Dip Rake
NP1 135 50 -85
NP2 307 40 -96
Principal Axes:
Axis Value Plunge Azimuth
T 8.22e+20 5 221
N 0.00e+00 4 312
P -8.22e+20 84 80
Moment Tensor: (dyne-cm)
Component Value
Mxx 4.58e+20
Mxy 4.03e+20
Mxz -6.80e+19
Myy 3.48e+20
Myz -1.33e+20
Mzz -8.07e+20
##############
######################
############################
#--------------###############
##-------------------#############
###----------------------###########
####------------------------##########
#####--------------------------#########
######---------------------------#######
#######---------------- ---------#######
########--------------- P ----------######
#########-------------- -----------#####
##########---------------------------#####
###########--------------------------###
############-------------------------###
#############-----------------------##
##############---------------------#
################------------------
# ##############------------
T #########################
######################
##############
Global CMT Convention Moment Tensor:
R T P
-8.07e+20 -6.80e+19 1.33e+20
-6.80e+19 4.58e+20 -4.03e+20
1.33e+20 -4.03e+20 3.48e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090412180516/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 30 -90 3.09 0.4357
WVFGRD96 1.0 140 50 -80 3.13 0.4675
WVFGRD96 2.0 135 50 -85 3.21 0.4748
WVFGRD96 3.0 340 50 -50 3.17 0.3494
WVFGRD96 4.0 340 60 -60 3.16 0.2829
WVFGRD96 5.0 340 60 -60 3.23 0.2783
WVFGRD96 6.0 25 30 -30 3.20 0.2869
WVFGRD96 7.0 25 30 -30 3.21 0.3025
WVFGRD96 8.0 30 35 -20 3.18 0.3099
WVFGRD96 9.0 35 35 -15 3.19 0.3144
WVFGRD96 10.0 35 35 -10 3.20 0.3162
WVFGRD96 11.0 50 35 15 3.22 0.3205
WVFGRD96 12.0 50 35 15 3.23 0.3240
WVFGRD96 13.0 55 35 25 3.24 0.3271
WVFGRD96 14.0 55 35 25 3.25 0.3285
WVFGRD96 15.0 305 55 70 3.32 0.3322
WVFGRD96 16.0 305 55 70 3.33 0.3374
WVFGRD96 17.0 310 60 75 3.33 0.3422
WVFGRD96 18.0 305 60 70 3.35 0.3470
WVFGRD96 19.0 305 60 70 3.36 0.3493
WVFGRD96 20.0 315 55 80 3.37 0.3513
WVFGRD96 21.0 315 55 85 3.38 0.3523
WVFGRD96 22.0 315 55 85 3.39 0.3514
WVFGRD96 23.0 145 35 95 3.40 0.3458
WVFGRD96 24.0 320 55 90 3.40 0.3371
WVFGRD96 25.0 135 35 80 3.41 0.3238
WVFGRD96 26.0 130 35 70 3.41 0.3089
WVFGRD96 27.0 120 70 60 3.41 0.3131
WVFGRD96 28.0 120 70 60 3.42 0.3169
WVFGRD96 29.0 125 65 65 3.44 0.3202
The best solution is
WVFGRD96 2.0 135 50 -85 3.21 0.4748
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=Mon Apr 20 15:57:35 CDT 2009