2009/06/23 20:58:50 42.445 13.360 13.0 3.20 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/06/23 20:58:50:0 42.44 13.36 13.0 3.2 Italy
Stations used:
IV.ARVD IV.CAMP IV.CERT IV.FIAM IV.GUMA IV.LPEL IV.MNS
IV.NRCA IV.OFFI IV.TERO MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 6.03e+20 dyne-cm
Mw = 3.12
Z = 10 km
Plane Strike Dip Rake
NP1 313 76 -104
NP2 180 20 -45
Principal Axes:
Axis Value Plunge Azimuth
T 6.03e+20 30 55
N 0.00e+00 14 317
P -6.03e+20 57 205
Moment Tensor: (dyne-cm)
Component Value
Mxx -2.55e+13
Mxy 1.46e+20
Mxz 4.00e+20
Myy 2.74e+20
Myz 3.26e+20
Mzz -2.74e+20
---###########
---###################
----########################
#--###########################
####---###########################
####-------################## ####
####-----------############### T #####
####--------------############# ######
####----------------####################
####-------------------###################
####---------------------#################
####-----------------------###############
####-------------------------#############
####-------------------------###########
####----------- -------------#########
####---------- P --------------#######
####--------- ---------------#####
####---------------------------###
###---------------------------
####------------------------
###-------------------
###-----------
Global CMT Convention Moment Tensor:
R T P
-2.74e+20 4.00e+20 -3.26e+20
4.00e+20 -2.55e+13 -1.46e+20
-3.26e+20 -1.46e+20 2.74e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090623205850/index.html
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STK = 180
DIP = 20
RAKE = -45
MW = 3.12
HS = 10.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/06/23 20:58:50:0 42.44 13.36 13.0 3.2 Italy
Stations used:
IV.ARVD IV.CAMP IV.CERT IV.FIAM IV.GUMA IV.LPEL IV.MNS
IV.NRCA IV.OFFI IV.TERO MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 6.03e+20 dyne-cm
Mw = 3.12
Z = 10 km
Plane Strike Dip Rake
NP1 313 76 -104
NP2 180 20 -45
Principal Axes:
Axis Value Plunge Azimuth
T 6.03e+20 30 55
N 0.00e+00 14 317
P -6.03e+20 57 205
Moment Tensor: (dyne-cm)
Component Value
Mxx -2.55e+13
Mxy 1.46e+20
Mxz 4.00e+20
Myy 2.74e+20
Myz 3.26e+20
Mzz -2.74e+20
---###########
---###################
----########################
#--###########################
####---###########################
####-------################## ####
####-----------############### T #####
####--------------############# ######
####----------------####################
####-------------------###################
####---------------------#################
####-----------------------###############
####-------------------------#############
####-------------------------###########
####----------- -------------#########
####---------- P --------------#######
####--------- ---------------#####
####---------------------------###
###---------------------------
####------------------------
###-------------------
###-----------
Global CMT Convention Moment Tensor:
R T P
-2.74e+20 4.00e+20 -3.26e+20
4.00e+20 -2.55e+13 -1.46e+20
-3.26e+20 -1.46e+20 2.74e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090623205850/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 0.5 145 45 -85 2.89 0.3010
WVFGRD96 1.0 125 40 90 2.91 0.2804
WVFGRD96 2.0 195 15 -20 3.07 0.2941
WVFGRD96 3.0 195 15 -30 3.04 0.3869
WVFGRD96 4.0 195 20 -30 3.02 0.4390
WVFGRD96 5.0 185 15 -40 3.13 0.4817
WVFGRD96 6.0 180 20 -45 3.14 0.5160
WVFGRD96 7.0 180 20 -45 3.14 0.5428
WVFGRD96 8.0 175 20 -50 3.10 0.5564
WVFGRD96 9.0 175 20 -50 3.11 0.5633
WVFGRD96 10.0 180 20 -45 3.12 0.5661
WVFGRD96 11.0 190 25 -30 3.13 0.5641
WVFGRD96 12.0 190 25 -30 3.14 0.5601
WVFGRD96 13.0 195 25 -25 3.15 0.5533
WVFGRD96 14.0 195 25 -25 3.16 0.5452
WVFGRD96 15.0 195 25 -25 3.21 0.5355
WVFGRD96 16.0 195 25 -20 3.22 0.5239
WVFGRD96 17.0 190 25 -25 3.24 0.5118
WVFGRD96 18.0 190 25 -25 3.25 0.4988
WVFGRD96 19.0 185 25 -30 3.26 0.4853
WVFGRD96 20.0 185 25 -30 3.27 0.4728
WVFGRD96 21.0 165 25 -40 3.29 0.4634
WVFGRD96 22.0 170 30 -35 3.30 0.4590
WVFGRD96 23.0 170 30 -40 3.31 0.4554
WVFGRD96 24.0 170 30 -40 3.32 0.4497
WVFGRD96 25.0 170 30 -40 3.32 0.4413
WVFGRD96 26.0 170 30 -40 3.33 0.4301
WVFGRD96 27.0 175 30 -30 3.33 0.4175
WVFGRD96 28.0 175 25 -30 3.33 0.4070
WVFGRD96 29.0 240 25 25 3.33 0.4015
The best solution is
WVFGRD96 10.0 180 20 -45 3.12 0.5661
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=Tue Jun 23 20:00:12 CDT 2009