2009/04/06 12:55:16 42.372 13.353 10.8 3.50 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/06 12:55:16:0 42.37 13.35 10.8 3.5 Italy
Stations used:
IV.AOI IV.ASSB IV.CERT IV.FAGN IV.FDMO IV.INTR IV.LPEL
IV.MNS IV.MTCE IV.NRCA IV.OFFI
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 1.58e+21 dyne-cm
Mw = 3.40
Z = 6 km
Plane Strike Dip Rake
NP1 345 60 -80
NP2 146 31 -107
Principal Axes:
Axis Value Plunge Azimuth
T 1.58e+21 14 68
N 0.00e+00 9 160
P -1.58e+21 73 280
Moment Tensor: (dyne-cm)
Component Value
Mxx 2.10e+20
Mxy 5.44e+20
Mxz 6.91e+19
Myy 1.14e+21
Myz 7.89e+20
Mzz -1.35e+21
---###########
---------#############
#-------------##############
#----------------#############
##------------------##############
###-------------------##############
###---------------------########## #
####----------------------######### T ##
####-----------------------######## ##
#####---------- ----------##############
#####---------- P -----------#############
######--------- -----------#############
######-----------------------#############
######-----------------------###########
#######----------------------###########
#######---------------------##########
########-------------------#########
#########----------------#########
#########--------------#######
###########----------#######
#############-----###-
#############-
Global CMT Convention Moment Tensor:
R T P
-1.35e+21 6.91e+19 -7.89e+20
6.91e+19 2.10e+20 -5.44e+20
-7.89e+20 -5.44e+20 1.14e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090406125516/index.html
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STK = 345
DIP = 60
RAKE = -80
MW = 3.40
HS = 6.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/06 12:55:16:0 42.37 13.35 10.8 3.5 Italy
Stations used:
IV.AOI IV.ASSB IV.CERT IV.FAGN IV.FDMO IV.INTR IV.LPEL
IV.MNS IV.MTCE IV.NRCA IV.OFFI
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 1.58e+21 dyne-cm
Mw = 3.40
Z = 6 km
Plane Strike Dip Rake
NP1 345 60 -80
NP2 146 31 -107
Principal Axes:
Axis Value Plunge Azimuth
T 1.58e+21 14 68
N 0.00e+00 9 160
P -1.58e+21 73 280
Moment Tensor: (dyne-cm)
Component Value
Mxx 2.10e+20
Mxy 5.44e+20
Mxz 6.91e+19
Myy 1.14e+21
Myz 7.89e+20
Mzz -1.35e+21
---###########
---------#############
#-------------##############
#----------------#############
##------------------##############
###-------------------##############
###---------------------########## #
####----------------------######### T ##
####-----------------------######## ##
#####---------- ----------##############
#####---------- P -----------#############
######--------- -----------#############
######-----------------------#############
######-----------------------###########
#######----------------------###########
#######---------------------##########
########-------------------#########
#########----------------#########
#########--------------#######
###########----------#######
#############-----###-
#############-
Global CMT Convention Moment Tensor:
R T P
-1.35e+21 6.91e+19 -7.89e+20
6.91e+19 2.10e+20 -5.44e+20
-7.89e+20 -5.44e+20 1.14e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090406125516/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 0.5 175 40 -70 3.11 0.2917
WVFGRD96 1.0 190 35 -45 3.16 0.2768
WVFGRD96 2.0 195 30 -30 3.25 0.3231
WVFGRD96 3.0 355 75 -75 3.28 0.3845
WVFGRD96 4.0 350 65 -75 3.29 0.4294
WVFGRD96 5.0 345 65 -80 3.39 0.4669
WVFGRD96 6.0 345 60 -80 3.40 0.4786
WVFGRD96 7.0 350 60 -75 3.38 0.4627
WVFGRD96 8.0 5 65 -50 3.34 0.4282
WVFGRD96 9.0 10 70 -45 3.34 0.4167
WVFGRD96 10.0 10 75 -40 3.35 0.4036
WVFGRD96 11.0 15 75 -35 3.36 0.3902
WVFGRD96 12.0 15 75 -35 3.37 0.3773
WVFGRD96 13.0 15 75 -35 3.38 0.3642
WVFGRD96 14.0 15 75 -35 3.38 0.3536
WVFGRD96 15.0 15 75 -40 3.41 0.3494
WVFGRD96 16.0 15 75 -40 3.42 0.3417
WVFGRD96 17.0 15 75 -35 3.43 0.3359
WVFGRD96 18.0 200 80 25 3.44 0.3291
WVFGRD96 19.0 200 80 25 3.44 0.3269
WVFGRD96 20.0 200 80 25 3.45 0.3251
WVFGRD96 21.0 200 80 25 3.46 0.3235
WVFGRD96 22.0 200 80 25 3.47 0.3221
WVFGRD96 23.0 200 80 25 3.48 0.3203
WVFGRD96 24.0 195 90 25 3.49 0.3193
WVFGRD96 25.0 195 90 25 3.50 0.3201
WVFGRD96 26.0 195 90 25 3.51 0.3205
WVFGRD96 27.0 195 90 25 3.52 0.3195
WVFGRD96 28.0 195 90 25 3.53 0.3178
WVFGRD96 29.0 195 85 25 3.54 0.3174
The best solution is
WVFGRD96 6.0 345 60 -80 3.40 0.4786
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 10:26:00 CDT 2009