2009/04/09 06:10:29 42.491 13.397 9.4 3.10 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/09 06:10:29:0 42.49 13.40 9.4 3.1 Italy
Stations used:
IV.CERT IV.FIAM IV.MNS 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 = 5 km
Plane Strike Dip Rake
NP1 200 65 -55
NP2 321 42 -141
Principal Axes:
Axis Value Plunge Azimuth
T 4.57e+20 13 265
N 0.00e+00 31 4
P -4.57e+20 55 156
Moment Tensor: (dyne-cm)
Component Value
Mxx -1.19e+20
Mxy 8.98e+19
Mxz 1.86e+20
Myy 4.06e+20
Myz -1.88e+20
Mzz -2.87e+20
--------------
---------------#######
############----############
###############--#############
################------############
################---------###########
################------------##########
################--------------##########
###############----------------#########
###############------------------#########
# ###########-------------------########
# T ##########---------------------#######
# ##########---------------------#######
############-----------------------#####
############---------- ----------#####
###########---------- P ----------####
#########----------- ----------###
########------------------------##
#######----------------------#
######---------------------#
###-------------------
--------------
Global CMT Convention Moment Tensor:
R T P
-2.87e+20 1.86e+20 1.88e+20
1.86e+20 -1.19e+20 -8.98e+19
1.88e+20 -8.98e+19 4.06e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090409061029/index.html
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STK = 200
DIP = 65
RAKE = -55
MW = 3.04
HS = 5.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/09 06:10:29:0 42.49 13.40 9.4 3.1 Italy
Stations used:
IV.CERT IV.FIAM IV.MNS 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 = 5 km
Plane Strike Dip Rake
NP1 200 65 -55
NP2 321 42 -141
Principal Axes:
Axis Value Plunge Azimuth
T 4.57e+20 13 265
N 0.00e+00 31 4
P -4.57e+20 55 156
Moment Tensor: (dyne-cm)
Component Value
Mxx -1.19e+20
Mxy 8.98e+19
Mxz 1.86e+20
Myy 4.06e+20
Myz -1.88e+20
Mzz -2.87e+20
--------------
---------------#######
############----############
###############--#############
################------############
################---------###########
################------------##########
################--------------##########
###############----------------#########
###############------------------#########
# ###########-------------------########
# T ##########---------------------#######
# ##########---------------------#######
############-----------------------#####
############---------- ----------#####
###########---------- P ----------####
#########----------- ----------###
########------------------------##
#######----------------------#
######---------------------#
###-------------------
--------------
Global CMT Convention Moment Tensor:
R T P
-2.87e+20 1.86e+20 1.88e+20
1.86e+20 -1.19e+20 -8.98e+19
1.88e+20 -8.98e+19 4.06e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090409061029/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.
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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 25 45 -10 2.72 0.2950
WVFGRD96 1.0 25 55 -10 2.70 0.3082
WVFGRD96 2.0 200 70 -45 2.83 0.3524
WVFGRD96 3.0 200 65 -50 2.92 0.4077
WVFGRD96 4.0 200 70 -45 2.94 0.4417
WVFGRD96 5.0 200 65 -55 3.04 0.4657
WVFGRD96 6.0 205 75 -55 3.07 0.4649
WVFGRD96 7.0 210 80 -55 3.11 0.4629
WVFGRD96 8.0 205 75 -45 3.05 0.4626
WVFGRD96 9.0 205 80 -35 3.02 0.4604
WVFGRD96 10.0 205 80 -40 3.05 0.4569
WVFGRD96 11.0 205 80 -35 3.05 0.4525
WVFGRD96 12.0 205 80 -30 3.05 0.4469
WVFGRD96 13.0 205 80 -30 3.06 0.4402
WVFGRD96 14.0 40 80 30 3.08 0.4337
WVFGRD96 15.0 40 80 30 3.10 0.4299
WVFGRD96 16.0 30 80 20 3.05 0.4265
WVFGRD96 17.0 30 80 20 3.07 0.4225
WVFGRD96 18.0 30 80 15 3.07 0.4186
WVFGRD96 19.0 30 80 15 3.08 0.4139
WVFGRD96 20.0 40 75 20 3.12 0.4099
WVFGRD96 21.0 40 75 20 3.12 0.4047
WVFGRD96 22.0 40 70 15 3.12 0.4000
WVFGRD96 23.0 40 70 15 3.13 0.3949
WVFGRD96 24.0 25 75 5 3.10 0.3894
WVFGRD96 25.0 25 75 0 3.12 0.3850
WVFGRD96 26.0 25 75 0 3.13 0.3810
WVFGRD96 27.0 25 75 -5 3.14 0.3783
WVFGRD96 28.0 25 75 -10 3.16 0.3784
WVFGRD96 29.0 25 75 -10 3.18 0.3818
The best solution is
WVFGRD96 5.0 200 65 -55 3.04 0.4657
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 08:57:36 CDT 2009