2009/04/11 06:57:02 42.387 13.406 10.5 3.20 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/11 06:57:02:0 42.39 13.41 10.5 3.2 Italy
Stations used:
IV.CERA IV.CERT IV.CESI IV.CESX IV.CING IV.FAGN IV.FIAM
IV.GUAR IV.INTR IV.LNSS IV.MNS IV.MTCE IV.MURB IV.NRCA
IV.RMP IV.TERO IV.VVLD
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 9.77e+20 dyne-cm
Mw = 3.26
Z = 8 km
Plane Strike Dip Rake
NP1 322 45 -85
NP2 135 45 -95
Principal Axes:
Axis Value Plunge Azimuth
T 9.77e+20 0 49
N 0.00e+00 4 139
P -9.77e+20 86 317
Moment Tensor: (dyne-cm)
Component Value
Mxx 4.27e+20
Mxy 4.87e+20
Mxz -4.26e+19
Myy 5.47e+20
Myz 4.26e+19
Mzz -9.74e+20
##############
######################
-----------################
----------------############ T
##-------------------######### #
##----------------------############
###------------------------###########
#####------------------------###########
#####----------- -----------##########
######----------- P ------------##########
#######---------- -------------#########
########--------------------------########
#########--------------------------#######
#########-------------------------######
###########-----------------------######
###########----------------------#####
#############-------------------####
##############-----------------###
################-------------#
###########################-
######################
##############
Global CMT Convention Moment Tensor:
R T P
-9.74e+20 -4.26e+19 -4.26e+19
-4.26e+19 4.27e+20 -4.87e+20
-4.26e+19 -4.87e+20 5.47e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090411065702/index.html
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STK = 135
DIP = 45
RAKE = -95
MW = 3.26
HS = 8.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/11 06:57:02:0 42.39 13.41 10.5 3.2 Italy
Stations used:
IV.CERA IV.CERT IV.CESI IV.CESX IV.CING IV.FAGN IV.FIAM
IV.GUAR IV.INTR IV.LNSS IV.MNS IV.MTCE IV.MURB IV.NRCA
IV.RMP IV.TERO IV.VVLD
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 9.77e+20 dyne-cm
Mw = 3.26
Z = 8 km
Plane Strike Dip Rake
NP1 322 45 -85
NP2 135 45 -95
Principal Axes:
Axis Value Plunge Azimuth
T 9.77e+20 0 49
N 0.00e+00 4 139
P -9.77e+20 86 317
Moment Tensor: (dyne-cm)
Component Value
Mxx 4.27e+20
Mxy 4.87e+20
Mxz -4.26e+19
Myy 5.47e+20
Myz 4.26e+19
Mzz -9.74e+20
##############
######################
-----------################
----------------############ T
##-------------------######### #
##----------------------############
###------------------------###########
#####------------------------###########
#####----------- -----------##########
######----------- P ------------##########
#######---------- -------------#########
########--------------------------########
#########--------------------------#######
#########-------------------------######
###########-----------------------######
###########----------------------#####
#############-------------------####
##############-----------------###
################-------------#
###########################-
######################
##############
Global CMT Convention Moment Tensor:
R T P
-9.74e+20 -4.26e+19 -4.26e+19
-4.26e+19 4.27e+20 -4.87e+20
-4.26e+19 -4.87e+20 5.47e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090411065702/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 0.5 295 35 90 2.98 0.2607
WVFGRD96 1.0 265 25 50 3.05 0.2274
WVFGRD96 2.0 250 15 40 3.15 0.2702
WVFGRD96 3.0 230 20 20 3.12 0.3350
WVFGRD96 4.0 215 30 10 3.10 0.3745
WVFGRD96 5.0 320 65 -90 3.24 0.4002
WVFGRD96 6.0 135 50 -95 3.29 0.4903
WVFGRD96 7.0 135 45 -95 3.29 0.5544
WVFGRD96 8.0 135 45 -95 3.26 0.5660
WVFGRD96 9.0 320 45 -90 3.26 0.5619
WVFGRD96 10.0 325 45 -85 3.26 0.5478
WVFGRD96 11.0 325 45 -85 3.26 0.5281
WVFGRD96 12.0 325 45 -85 3.27 0.5038
WVFGRD96 13.0 330 50 -75 3.26 0.4779
WVFGRD96 14.0 330 50 -75 3.27 0.4519
WVFGRD96 15.0 330 50 -75 3.30 0.4355
WVFGRD96 16.0 330 50 -75 3.30 0.4102
WVFGRD96 17.0 155 30 -75 3.30 0.3872
WVFGRD96 18.0 160 30 -70 3.30 0.3713
WVFGRD96 19.0 160 30 -70 3.31 0.3553
WVFGRD96 20.0 170 30 -55 3.31 0.3411
WVFGRD96 21.0 0 70 -20 3.34 0.3296
WVFGRD96 22.0 0 70 -20 3.35 0.3205
WVFGRD96 23.0 0 75 -20 3.36 0.3117
WVFGRD96 24.0 0 75 -20 3.37 0.3025
WVFGRD96 25.0 310 70 70 3.35 0.2983
WVFGRD96 26.0 310 70 70 3.36 0.3027
WVFGRD96 27.0 310 70 70 3.37 0.3057
WVFGRD96 28.0 305 70 65 3.37 0.3064
WVFGRD96 29.0 305 70 65 3.38 0.3049
The best solution is
WVFGRD96 8.0 135 45 -95 3.26 0.5660
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 27 15:51:47 CDT 2009