2009/06/28 17:57:27 44.300 9.949 5.4 3.30 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/06/28 17:57:27:0 44.30 9.95 5.4 3.3 Italy
Stations used:
IG.FINB IG.MAIM IG.PCP IG.SC2M IV.ASQU IV.BDI IV.FNVD
IV.QLNO MN.VLC
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 8.81e+20 dyne-cm
Mw = 3.23
Z = 6 km
Plane Strike Dip Rake
NP1 335 60 -65
NP2 112 38 -126
Principal Axes:
Axis Value Plunge Azimuth
T 8.81e+20 12 47
N 0.00e+00 21 142
P -8.81e+20 65 291
Moment Tensor: (dyne-cm)
Component Value
Mxx 3.71e+20
Mxy 4.72e+20
Mxz 1.36e+14
Myy 3.21e+20
Myz 4.41e+20
Mzz -6.92e+20
##############
-----#################
-----------#################
--------------#############
------------------########### T ##
---------------------######### ###
-----------------------###############
#------------------------###############
#----------- -----------##############
##----------- P ------------##############
###---------- -------------#############
####--------------------------############
#####-------------------------############
#####-------------------------##########
#######-----------------------##########
########---------------------#########
##########------------------######--
#############--------------###----
#########################-----
########################----
####################--
##############
Global CMT Convention Moment Tensor:
R T P
-6.92e+20 1.36e+14 -4.41e+20
1.36e+14 3.71e+20 -4.72e+20
-4.41e+20 -4.72e+20 3.21e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090628175727/index.html
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STK = 335
DIP = 60
RAKE = -65
MW = 3.23
HS = 6.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/06/28 17:57:27:0 44.30 9.95 5.4 3.3 Italy
Stations used:
IG.FINB IG.MAIM IG.PCP IG.SC2M IV.ASQU IV.BDI IV.FNVD
IV.QLNO MN.VLC
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 8.81e+20 dyne-cm
Mw = 3.23
Z = 6 km
Plane Strike Dip Rake
NP1 335 60 -65
NP2 112 38 -126
Principal Axes:
Axis Value Plunge Azimuth
T 8.81e+20 12 47
N 0.00e+00 21 142
P -8.81e+20 65 291
Moment Tensor: (dyne-cm)
Component Value
Mxx 3.71e+20
Mxy 4.72e+20
Mxz 1.36e+14
Myy 3.21e+20
Myz 4.41e+20
Mzz -6.92e+20
##############
-----#################
-----------#################
--------------#############
------------------########### T ##
---------------------######### ###
-----------------------###############
#------------------------###############
#----------- -----------##############
##----------- P ------------##############
###---------- -------------#############
####--------------------------############
#####-------------------------############
#####-------------------------##########
#######-----------------------##########
########---------------------#########
##########------------------######--
#############--------------###----
#########################-----
########################----
####################--
##############
Global CMT Convention Moment Tensor:
R T P
-6.92e+20 1.36e+14 -4.41e+20
1.36e+14 3.71e+20 -4.72e+20
-4.41e+20 -4.72e+20 3.21e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090628175727/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 60 35 -70 2.93 0.3574
WVFGRD96 1.0 195 90 70 3.06 0.3419
WVFGRD96 2.0 365 85 -70 3.12 0.4330
WVFGRD96 3.0 350 75 -65 3.11 0.4993
WVFGRD96 4.0 335 60 -60 3.16 0.5365
WVFGRD96 5.0 335 65 -65 3.23 0.5467
WVFGRD96 6.0 335 60 -65 3.23 0.5515
WVFGRD96 7.0 340 60 -60 3.22 0.5429
WVFGRD96 8.0 340 55 -50 3.20 0.5278
WVFGRD96 9.0 195 60 45 3.18 0.5220
WVFGRD96 10.0 190 65 40 3.18 0.5142
WVFGRD96 11.0 185 70 35 3.20 0.5008
WVFGRD96 12.0 185 70 35 3.21 0.4867
WVFGRD96 13.0 185 75 30 3.21 0.4726
WVFGRD96 14.0 185 75 30 3.22 0.4583
WVFGRD96 15.0 185 70 35 3.25 0.4438
WVFGRD96 16.0 185 70 30 3.26 0.4316
WVFGRD96 17.0 185 70 30 3.27 0.4184
WVFGRD96 18.0 185 70 30 3.28 0.4045
WVFGRD96 19.0 185 75 30 3.27 0.3889
WVFGRD96 20.0 190 75 35 3.26 0.3745
WVFGRD96 21.0 15 45 35 3.31 0.3608
WVFGRD96 22.0 15 45 35 3.31 0.3516
WVFGRD96 23.0 10 50 30 3.32 0.3464
WVFGRD96 24.0 5 55 25 3.34 0.3435
WVFGRD96 25.0 190 70 35 3.32 0.3434
WVFGRD96 26.0 185 75 30 3.34 0.3426
WVFGRD96 27.0 175 85 15 3.39 0.3402
WVFGRD96 28.0 175 85 15 3.41 0.3378
WVFGRD96 29.0 175 90 10 3.43 0.3336
The best solution is
WVFGRD96 6.0 335 60 -65 3.23 0.5515
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 Jun 29 07:15:34 CDT 2009