2009/04/09 02:37:26 42.498 13.335 10.4 3.10 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/09 02:37:26:0 42.50 13.34 10.4 3.1 Italy
Stations used:
IV.CESX IV.FDMO IV.FIAM IV.GUAR IV.INTR IV.LATE IV.MIDA
IV.MNS IV.MTCE IV.OFFI IV.RDP IV.SACS IV.TERO IV.TOLF
IV.TRTR 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 = 7 km
Plane Strike Dip Rake
NP1 311 65 -88
NP2 125 25 -95
Principal Axes:
Axis Value Plunge Azimuth
T 7.67e+20 20 39
N 0.00e+00 2 130
P -7.67e+20 70 225
Moment Tensor: (dyne-cm)
Component Value
Mxx 3.66e+20
Mxy 2.85e+20
Mxz 3.68e+20
Myy 2.19e+20
Myz 3.31e+20
Mzz -5.86e+20
##############
######################
####################### ##
######################## T ###
---------################# #####
--------------######################
#-----------------####################
##--------------------##################
##----------------------################
###------------------------###############
###--------------------------#############
###----------------------------###########
####----------- --------------##########
####---------- P ---------------########
#####--------- ----------------#######
#####----------------------------#####
######---------------------------###
#######--------------------------#
#######----------------------#
##########---------------###
######################
##############
Global CMT Convention Moment Tensor:
R T P
-5.86e+20 3.68e+20 -3.31e+20
3.68e+20 3.66e+20 -2.85e+20
-3.31e+20 -2.85e+20 2.19e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090409023726/index.html
|
STK = 125
DIP = 25
RAKE = -95
MW = 3.19
HS = 7.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/09 02:37:26:0 42.50 13.34 10.4 3.1 Italy
Stations used:
IV.CESX IV.FDMO IV.FIAM IV.GUAR IV.INTR IV.LATE IV.MIDA
IV.MNS IV.MTCE IV.OFFI IV.RDP IV.SACS IV.TERO IV.TOLF
IV.TRTR 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 = 7 km
Plane Strike Dip Rake
NP1 311 65 -88
NP2 125 25 -95
Principal Axes:
Axis Value Plunge Azimuth
T 7.67e+20 20 39
N 0.00e+00 2 130
P -7.67e+20 70 225
Moment Tensor: (dyne-cm)
Component Value
Mxx 3.66e+20
Mxy 2.85e+20
Mxz 3.68e+20
Myy 2.19e+20
Myz 3.31e+20
Mzz -5.86e+20
##############
######################
####################### ##
######################## T ###
---------################# #####
--------------######################
#-----------------####################
##--------------------##################
##----------------------################
###------------------------###############
###--------------------------#############
###----------------------------###########
####----------- --------------##########
####---------- P ---------------########
#####--------- ----------------#######
#####----------------------------#####
######---------------------------###
#######--------------------------#
#######----------------------#
##########---------------###
######################
##############
Global CMT Convention Moment Tensor:
R T P
-5.86e+20 3.68e+20 -3.31e+20
3.68e+20 3.66e+20 -2.85e+20
-3.31e+20 -2.85e+20 2.19e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090409023726/index.html
|
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.
|
|
|
|
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 0.5 130 50 -95 2.91 0.4176
WVFGRD96 1.0 350 45 -45 2.95 0.3790
WVFGRD96 2.0 115 10 -105 3.09 0.3834
WVFGRD96 3.0 310 80 -85 3.07 0.4823
WVFGRD96 4.0 310 75 -85 3.05 0.5380
WVFGRD96 5.0 125 20 -95 3.18 0.5773
WVFGRD96 6.0 310 65 -90 3.19 0.6023
WVFGRD96 7.0 125 25 -95 3.19 0.6060
WVFGRD96 8.0 310 60 -85 3.16 0.5809
WVFGRD96 9.0 310 65 -85 3.14 0.5606
WVFGRD96 10.0 310 65 -85 3.14 0.5348
WVFGRD96 11.0 310 70 -80 3.14 0.5074
WVFGRD96 12.0 315 75 -65 3.14 0.4826
WVFGRD96 13.0 320 80 -60 3.15 0.4600
WVFGRD96 14.0 315 80 -60 3.15 0.4392
WVFGRD96 15.0 315 80 -65 3.19 0.4202
WVFGRD96 16.0 320 85 -60 3.19 0.3994
WVFGRD96 17.0 315 85 -60 3.20 0.3798
WVFGRD96 18.0 320 90 -60 3.20 0.3619
WVFGRD96 19.0 145 85 60 3.21 0.3492
WVFGRD96 20.0 150 80 65 3.21 0.3379
WVFGRD96 21.0 150 75 65 3.22 0.3285
WVFGRD96 22.0 300 20 65 3.23 0.3243
WVFGRD96 23.0 290 25 50 3.25 0.3217
WVFGRD96 24.0 295 25 50 3.26 0.3197
WVFGRD96 25.0 295 25 50 3.27 0.3184
WVFGRD96 26.0 295 25 50 3.27 0.3165
WVFGRD96 27.0 290 25 50 3.28 0.3151
WVFGRD96 28.0 285 25 45 3.29 0.3173
WVFGRD96 29.0 290 25 50 3.29 0.3191
The best solution is
WVFGRD96 7.0 125 25 -95 3.19 0.6060
The mechanism correspond to the best fit is
|
|
|
The best fit as a function of depth is given in the following figure:
|
|
|
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
|
|
|
|
| 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 08:54:53 CDT 2009