2009/03/30 21:57:17 42.316 13.375 9.5 3.3 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/03/30 21:57:17:0 42.32 13.38 9.5 3.3 Italy
Stations used:
IV.CERT IV.GUAR IV.INTR IV.LPEL IV.MTCE IV.RMP IV.TERO
IV.TRTR
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 1.95e+21 dyne-cm
Mw = 3.46
Z = 11 km
Plane Strike Dip Rake
NP1 149 55 -93
NP2 335 35 -85
Principal Axes:
Axis Value Plunge Azimuth
T 1.95e+21 10 241
N 0.00e+00 3 151
P -1.95e+21 79 45
Moment Tensor: (dyne-cm)
Component Value
Mxx 4.01e+20
Mxy 7.62e+20
Mxz -4.07e+20
Myy 1.42e+21
Myz -5.43e+20
Mzz -1.83e+21
##############
-----------###########
###---------------##########
###------------------#########
#####--------------------#########
######----------------------########
#######-----------------------########
########------------------------########
#########------------ ---------#######
##########------------ P ---------########
###########----------- ----------#######
############-----------------------#######
############------------------------######
#############----------------------#####
## #########--------------------######
# T ##########-------------------#####
############-----------------####
################--------------####
################-----------###
##################-------###
####################-#
##############
Global CMT Convention Moment Tensor:
R T P
-1.83e+21 -4.07e+20 5.43e+20
-4.07e+20 4.01e+20 -7.62e+20
5.43e+20 -7.62e+20 1.42e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090330215717/index.html
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STK = 335
DIP = 35
RAKE = -85
MW = 3.46
HS = 11.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/03/30 21:57:17:0 42.32 13.38 9.5 3.3 Italy
Stations used:
IV.CERT IV.GUAR IV.INTR IV.LPEL IV.MTCE IV.RMP IV.TERO
IV.TRTR
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 1.95e+21 dyne-cm
Mw = 3.46
Z = 11 km
Plane Strike Dip Rake
NP1 149 55 -93
NP2 335 35 -85
Principal Axes:
Axis Value Plunge Azimuth
T 1.95e+21 10 241
N 0.00e+00 3 151
P -1.95e+21 79 45
Moment Tensor: (dyne-cm)
Component Value
Mxx 4.01e+20
Mxy 7.62e+20
Mxz -4.07e+20
Myy 1.42e+21
Myz -5.43e+20
Mzz -1.83e+21
##############
-----------###########
###---------------##########
###------------------#########
#####--------------------#########
######----------------------########
#######-----------------------########
########------------------------########
#########------------ ---------#######
##########------------ P ---------########
###########----------- ----------#######
############-----------------------#######
############------------------------######
#############----------------------#####
## #########--------------------######
# T ##########-------------------#####
############-----------------####
################--------------####
################-----------###
##################-------###
####################-#
##############
Global CMT Convention Moment Tensor:
R T P
-1.83e+21 -4.07e+20 5.43e+20
-4.07e+20 4.01e+20 -7.62e+20
5.43e+20 -7.62e+20 1.42e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090330215717/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 0.5 260 55 25 3.25 0.4171
WVFGRD96 1.0 260 60 25 3.29 0.4040
WVFGRD96 2.0 260 70 20 3.38 0.4024
WVFGRD96 3.0 245 40 5 3.35 0.4206
WVFGRD96 4.0 245 45 5 3.36 0.4588
WVFGRD96 5.0 240 30 10 3.42 0.4908
WVFGRD96 6.0 235 30 10 3.41 0.5161
WVFGRD96 7.0 230 30 0 3.42 0.5304
WVFGRD96 8.0 345 35 -75 3.43 0.5562
WVFGRD96 9.0 345 35 -75 3.44 0.5810
WVFGRD96 10.0 335 35 -85 3.45 0.5940
WVFGRD96 11.0 335 35 -85 3.46 0.5977
WVFGRD96 12.0 150 55 -90 3.47 0.5940
WVFGRD96 13.0 150 55 -90 3.47 0.5849
WVFGRD96 14.0 -15 35 -75 3.48 0.5729
WVFGRD96 15.0 10 30 -50 3.51 0.5664
WVFGRD96 16.0 15 25 -45 3.52 0.5577
WVFGRD96 17.0 10 25 -45 3.52 0.5473
WVFGRD96 18.0 20 25 -35 3.53 0.5351
WVFGRD96 19.0 25 25 -30 3.54 0.5213
WVFGRD96 20.0 45 30 -10 3.55 0.5095
WVFGRD96 21.0 50 30 0 3.56 0.5005
WVFGRD96 22.0 50 30 0 3.57 0.4909
WVFGRD96 23.0 55 30 5 3.58 0.4799
WVFGRD96 24.0 350 45 -50 3.60 0.4770
WVFGRD96 25.0 350 45 -50 3.61 0.4725
WVFGRD96 26.0 350 45 -50 3.62 0.4619
WVFGRD96 27.0 350 45 -50 3.63 0.4448
WVFGRD96 28.0 350 40 -55 3.63 0.4252
WVFGRD96 29.0 55 35 5 3.59 0.4114
The best solution is
WVFGRD96 11.0 335 35 -85 3.46 0.5977
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=Wed Sep 2 10:52:04 CDT 2009