2009/05/23 17:24:22 42.501 13.303 11.70 3.30 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/05/23 17:24:22:0 42.50 13.30 11.7 3.3 Italy
Stations used:
IV.CESX IV.GUAR IV.GUMA IV.LATE IV.LPEL IV.MNS IV.MTCE
IV.NRCA IV.OFFI IV.RMP 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 = 4.57e+20 dyne-cm
Mw = 3.04
Z = 6 km
Plane Strike Dip Rake
NP1 315 65 -90
NP2 135 25 -90
Principal Axes:
Axis Value Plunge Azimuth
T 4.57e+20 20 45
N 0.00e+00 -0 135
P -4.57e+20 70 225
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.75e+20
Mxy 1.75e+20
Mxz 2.08e+20
Myy 1.75e+20
Myz 2.08e+20
Mzz -3.50e+20
##############
######################
############################
-----#################### ##
#----------################ T ####
#---------------############ #####
##-----------------###################
##--------------------##################
##----------------------################
###------------------------###############
####-------------------------#############
####--------------------------############
#####---------- -------------###########
####---------- P ---------------########
#####--------- ---------------########
#####---------------------------######
######--------------------------####
#######------------------------###
#######-----------------------
#########------------------#
##############---#####
##############
Global CMT Convention Moment Tensor:
R T P
-3.50e+20 2.08e+20 -2.08e+20
2.08e+20 1.75e+20 -1.75e+20
-2.08e+20 -1.75e+20 1.75e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090523172422/index.html
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STK = 315
DIP = 65
RAKE = -90
MW = 3.04
HS = 6.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/05/23 17:24:22:0 42.50 13.30 11.7 3.3 Italy
Stations used:
IV.CESX IV.GUAR IV.GUMA IV.LATE IV.LPEL IV.MNS IV.MTCE
IV.NRCA IV.OFFI IV.RMP 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 = 4.57e+20 dyne-cm
Mw = 3.04
Z = 6 km
Plane Strike Dip Rake
NP1 315 65 -90
NP2 135 25 -90
Principal Axes:
Axis Value Plunge Azimuth
T 4.57e+20 20 45
N 0.00e+00 -0 135
P -4.57e+20 70 225
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.75e+20
Mxy 1.75e+20
Mxz 2.08e+20
Myy 1.75e+20
Myz 2.08e+20
Mzz -3.50e+20
##############
######################
############################
-----#################### ##
#----------################ T ####
#---------------############ #####
##-----------------###################
##--------------------##################
##----------------------################
###------------------------###############
####-------------------------#############
####--------------------------############
#####---------- -------------###########
####---------- P ---------------########
#####--------- ---------------########
#####---------------------------######
######--------------------------####
#######------------------------###
#######-----------------------
#########------------------#
##############---#####
##############
Global CMT Convention Moment Tensor:
R T P
-3.50e+20 2.08e+20 -2.08e+20
2.08e+20 1.75e+20 -1.75e+20
-2.08e+20 -1.75e+20 1.75e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090523172422/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 0.5 335 45 -65 2.77 0.3855
WVFGRD96 1.0 335 45 -65 2.81 0.3517
WVFGRD96 2.0 135 10 -90 2.95 0.3432
WVFGRD96 3.0 315 75 -90 2.93 0.4304
WVFGRD96 4.0 315 70 -90 2.93 0.4849
WVFGRD96 5.0 135 20 -90 3.03 0.5275
WVFGRD96 6.0 315 65 -90 3.04 0.5467
WVFGRD96 7.0 315 65 -85 3.03 0.5422
WVFGRD96 8.0 130 30 -95 3.00 0.5184
WVFGRD96 9.0 315 60 -85 3.00 0.4978
WVFGRD96 10.0 320 60 -80 2.99 0.4727
WVFGRD96 11.0 330 65 -65 2.99 0.4520
WVFGRD96 12.0 330 65 -65 2.99 0.4298
WVFGRD96 13.0 330 65 -65 2.99 0.4064
WVFGRD96 14.0 200 60 25 3.06 0.3875
WVFGRD96 15.0 335 70 -60 3.03 0.3741
WVFGRD96 16.0 205 55 20 3.11 0.3612
WVFGRD96 17.0 205 55 20 3.12 0.3515
WVFGRD96 18.0 205 55 20 3.12 0.3415
WVFGRD96 19.0 205 55 20 3.13 0.3313
WVFGRD96 20.0 205 55 20 3.14 0.3209
WVFGRD96 21.0 205 55 20 3.14 0.3109
WVFGRD96 22.0 205 55 20 3.15 0.3022
WVFGRD96 23.0 205 55 15 3.16 0.2941
WVFGRD96 24.0 205 55 15 3.17 0.2857
WVFGRD96 25.0 205 60 15 3.18 0.2797
WVFGRD96 26.0 205 60 15 3.18 0.2753
WVFGRD96 27.0 205 60 15 3.19 0.2716
WVFGRD96 28.0 205 60 15 3.20 0.2689
WVFGRD96 29.0 205 60 15 3.21 0.2718
The best solution is
WVFGRD96 6.0 315 65 -90 3.04 0.5467
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=Sun Aug 23 11:59:22 CDT 2009