2009/04/07 01:52:03 42.432 13.393 1.2 3.00 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/07 01:52:03:0 42.43 13.39 1.2 3.0 Italy
Stations used:
IV.AOI IV.ARVD IV.ASSB IV.CAFR IV.CERA IV.CERT IV.FDMO
IV.FIAM IV.GUAR IV.INTR IV.MGAB IV.MNS IV.MTCE IV.POFI
IV.RDP IV.RMP IV.SACS IV.TOLF
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 1.12e+21 dyne-cm
Mw = 3.30
Z = 8 km
Plane Strike Dip Rake
NP1 153 50 -94
NP2 340 40 -85
Principal Axes:
Axis Value Plunge Azimuth
T 1.12e+21 5 246
N 0.00e+00 3 156
P -1.12e+21 84 34
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.69e+20
Mxy 4.02e+20
Mxz -1.37e+20
Myy 9.32e+20
Myz -1.57e+20
Mzz -1.10e+21
-#############
#----------###########
###--------------###########
####----------------##########
#####-------------------##########
######---------------------#########
#######----------------------#########
########-----------------------#########
########------------------------########
##########---------- ----------#########
##########---------- P -----------########
###########--------- -----------########
###########-----------------------########
###########----------------------#######
#########---------------------#######
T ##########--------------------######
############------------------#####
#############----------------#####
#############-------------####
###############---------####
################----##
##############
Global CMT Convention Moment Tensor:
R T P
-1.10e+21 -1.37e+20 1.57e+20
-1.37e+20 1.69e+20 -4.02e+20
1.57e+20 -4.02e+20 9.32e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090407015203/index.html
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STK = 340
DIP = 40
RAKE = -85
MW = 3.30
HS = 8.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/07 01:52:03:0 42.43 13.39 1.2 3.0 Italy
Stations used:
IV.AOI IV.ARVD IV.ASSB IV.CAFR IV.CERA IV.CERT IV.FDMO
IV.FIAM IV.GUAR IV.INTR IV.MGAB IV.MNS IV.MTCE IV.POFI
IV.RDP IV.RMP IV.SACS IV.TOLF
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 1.12e+21 dyne-cm
Mw = 3.30
Z = 8 km
Plane Strike Dip Rake
NP1 153 50 -94
NP2 340 40 -85
Principal Axes:
Axis Value Plunge Azimuth
T 1.12e+21 5 246
N 0.00e+00 3 156
P -1.12e+21 84 34
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.69e+20
Mxy 4.02e+20
Mxz -1.37e+20
Myy 9.32e+20
Myz -1.57e+20
Mzz -1.10e+21
-#############
#----------###########
###--------------###########
####----------------##########
#####-------------------##########
######---------------------#########
#######----------------------#########
########-----------------------#########
########------------------------########
##########---------- ----------#########
##########---------- P -----------########
###########--------- -----------########
###########-----------------------########
###########----------------------#######
#########---------------------#######
T ##########--------------------######
############------------------#####
#############----------------#####
#############-------------####
###############---------####
################----##
##############
Global CMT Convention Moment Tensor:
R T P
-1.10e+21 -1.37e+20 1.57e+20
-1.37e+20 1.69e+20 -4.02e+20
1.57e+20 -4.02e+20 9.32e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090407015203/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 0.5 150 60 90 3.05 0.2865
WVFGRD96 1.0 255 30 20 3.13 0.2482
WVFGRD96 2.0 240 25 20 3.18 0.2841
WVFGRD96 3.0 235 30 20 3.16 0.3274
WVFGRD96 4.0 25 25 -35 3.16 0.3593
WVFGRD96 5.0 5 20 -60 3.28 0.4024
WVFGRD96 6.0 340 30 -85 3.32 0.4629
WVFGRD96 7.0 335 35 -90 3.33 0.5068
WVFGRD96 8.0 340 40 -85 3.30 0.5101
WVFGRD96 9.0 340 40 -85 3.29 0.4996
WVFGRD96 10.0 340 40 -85 3.29 0.4809
WVFGRD96 11.0 345 40 -80 3.29 0.4582
WVFGRD96 12.0 345 40 -80 3.29 0.4329
WVFGRD96 13.0 355 40 -65 3.29 0.4074
WVFGRD96 14.0 5 40 -55 3.29 0.3817
WVFGRD96 15.0 5 40 -50 3.33 0.3683
WVFGRD96 16.0 10 45 -40 3.33 0.3470
WVFGRD96 17.0 10 45 -40 3.34 0.3261
WVFGRD96 18.0 10 50 -35 3.35 0.3069
WVFGRD96 19.0 180 80 -35 3.40 0.2913
WVFGRD96 20.0 180 80 -35 3.41 0.2778
WVFGRD96 21.0 180 80 -35 3.41 0.2652
WVFGRD96 22.0 180 80 -35 3.41 0.2537
WVFGRD96 23.0 180 80 -35 3.42 0.2416
WVFGRD96 24.0 180 80 -35 3.42 0.2300
WVFGRD96 25.0 115 50 30 3.39 0.2237
WVFGRD96 26.0 115 55 35 3.40 0.2260
WVFGRD96 27.0 320 50 65 3.39 0.2337
WVFGRD96 28.0 325 50 75 3.41 0.2407
WVFGRD96 29.0 330 50 80 3.43 0.2481
The best solution is
WVFGRD96 8.0 340 40 -85 3.30 0.5101
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 15:16:29 CDT 2009