2009/04/08 17:58:35 42.364 13.396 8.8 3.20 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/08 17:58:35:0 42.36 13.40 8.8 3.2 Italy
Stations used:
IV.CAFR IV.CERT IV.CESX IV.CING IV.FAGN IV.FIAM IV.INTR
IV.MNS IV.MTCE IV.NRCA IV.OFFI IV.TERO
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 1.20e+21 dyne-cm
Mw = 3.32
Z = 2 km
Plane Strike Dip Rake
NP1 335 55 -75
NP2 130 38 -110
Principal Axes:
Axis Value Plunge Azimuth
T 1.20e+21 9 54
N 0.00e+00 12 146
P -1.20e+21 75 289
Moment Tensor: (dyne-cm)
Component Value
Mxx 3.90e+20
Mxy 5.82e+20
Mxz 6.10e+18
Myy 7.01e+20
Myz 4.35e+20
Mzz -1.09e+21
##############
------################
------------################
----------------#############
#-------------------########### T
#---------------------########## #
##----------------------##############
###------------------------#############
###-------------------------############
#####----------- ----------#############
#####----------- P -----------############
######---------- ------------###########
#######------------------------###########
#######------------------------#########
########-----------------------#########
#########---------------------########
##########-------------------#######
############----------------######
#############-------------####
########################----
####################--
##############
Global CMT Convention Moment Tensor:
R T P
-1.09e+21 6.10e+18 -4.35e+20
6.10e+18 3.90e+20 -5.82e+20
-4.35e+20 -5.82e+20 7.01e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090408175835/index.html
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STK = 335
DIP = 55
RAKE = -75
MW = 3.32
HS = 2.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/08 17:58:35:0 42.36 13.40 8.8 3.2 Italy
Stations used:
IV.CAFR IV.CERT IV.CESX IV.CING IV.FAGN IV.FIAM IV.INTR
IV.MNS IV.MTCE IV.NRCA IV.OFFI IV.TERO
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 1.20e+21 dyne-cm
Mw = 3.32
Z = 2 km
Plane Strike Dip Rake
NP1 335 55 -75
NP2 130 38 -110
Principal Axes:
Axis Value Plunge Azimuth
T 1.20e+21 9 54
N 0.00e+00 12 146
P -1.20e+21 75 289
Moment Tensor: (dyne-cm)
Component Value
Mxx 3.90e+20
Mxy 5.82e+20
Mxz 6.10e+18
Myy 7.01e+20
Myz 4.35e+20
Mzz -1.09e+21
##############
------################
------------################
----------------#############
#-------------------########### T
#---------------------########## #
##----------------------##############
###------------------------#############
###-------------------------############
#####----------- ----------#############
#####----------- P -----------############
######---------- ------------###########
#######------------------------###########
#######------------------------#########
########-----------------------#########
#########---------------------########
##########-------------------#######
############----------------######
#############-------------####
########################----
####################--
##############
Global CMT Convention Moment Tensor:
R T P
-1.09e+21 6.10e+18 -4.35e+20
6.10e+18 3.90e+20 -5.82e+20
-4.35e+20 -5.82e+20 7.01e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090408175835/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 0.5 345 65 -70 3.23 0.4694
WVFGRD96 1.0 335 55 -75 3.25 0.5244
WVFGRD96 2.0 335 55 -75 3.32 0.5485
WVFGRD96 3.0 170 50 -45 3.29 0.4567
WVFGRD96 4.0 180 60 -30 3.27 0.3984
WVFGRD96 5.0 175 50 -35 3.33 0.3735
WVFGRD96 6.0 25 45 30 3.36 0.3761
WVFGRD96 7.0 25 45 30 3.37 0.3824
WVFGRD96 8.0 25 50 30 3.36 0.3882
WVFGRD96 9.0 40 45 30 3.37 0.3833
WVFGRD96 10.0 40 45 30 3.38 0.3838
WVFGRD96 11.0 40 45 30 3.39 0.3821
WVFGRD96 12.0 40 45 30 3.40 0.3783
WVFGRD96 13.0 45 45 35 3.41 0.3728
WVFGRD96 14.0 45 45 35 3.42 0.3669
WVFGRD96 15.0 50 35 45 3.47 0.3574
WVFGRD96 16.0 195 40 15 3.43 0.3510
WVFGRD96 17.0 305 60 65 3.45 0.3490
WVFGRD96 18.0 305 60 65 3.46 0.3498
WVFGRD96 19.0 305 60 65 3.47 0.3486
WVFGRD96 20.0 305 60 65 3.48 0.3446
WVFGRD96 21.0 160 55 -70 3.49 0.3391
WVFGRD96 22.0 165 55 -60 3.50 0.3424
WVFGRD96 23.0 165 55 -60 3.51 0.3455
WVFGRD96 24.0 165 55 -60 3.52 0.3475
WVFGRD96 25.0 165 50 -60 3.52 0.3492
WVFGRD96 26.0 160 50 -65 3.53 0.3506
WVFGRD96 27.0 165 50 -60 3.54 0.3488
WVFGRD96 28.0 165 50 -60 3.55 0.3436
WVFGRD96 29.0 165 50 -65 3.56 0.3376
The best solution is
WVFGRD96 2.0 335 55 -75 3.32 0.5485
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=Fri May 1 07:35:04 CDT 2009