2009/07/15 00:58:06 42.466 13.284 10.0 3.00 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/07/15 00:58:06:0 42.47 13.28 10.0 3.0 Italy
Stations used:
IV.FDMO IV.FIAM IV.GUMA IV.MNS IV.TERO MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 1.68e+20 dyne-cm
Mw = 2.75
Z = 4 km
Plane Strike Dip Rake
NP1 125 60 -65
NP2 262 38 -126
Principal Axes:
Axis Value Plunge Azimuth
T 1.68e+20 12 197
N 0.00e+00 21 292
P -1.68e+20 65 81
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.46e+20
Mxy 4.09e+19
Mxz -4.20e+19
Myy -1.44e+19
Myz -7.27e+19
Mzz -1.32e+20
##############
######################
############################
##############################
############-------------#########
-#######-----------------------#####
---###-----------------------------###
--------------------------------------##
---##----------------------------------#
---#####------------------ -------------
--#######----------------- P -------------
-##########--------------- -------------
############------------------------------
##############--------------------------
################------------------------
##################--------------------
#####################---------------
##########################--------
##############################
####### ##################
#### T ###############
###########
Global CMT Convention Moment Tensor:
R T P
-1.32e+20 -4.20e+19 7.27e+19
-4.20e+19 1.46e+20 -4.09e+19
7.27e+19 -4.09e+19 -1.44e+19
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090715005806/index.html
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STK = 125
DIP = 60
RAKE = -65
MW = 2.75
HS = 4.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/07/15 00:58:06:0 42.47 13.28 10.0 3.0 Italy
Stations used:
IV.FDMO IV.FIAM IV.GUMA IV.MNS IV.TERO MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 1.68e+20 dyne-cm
Mw = 2.75
Z = 4 km
Plane Strike Dip Rake
NP1 125 60 -65
NP2 262 38 -126
Principal Axes:
Axis Value Plunge Azimuth
T 1.68e+20 12 197
N 0.00e+00 21 292
P -1.68e+20 65 81
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.46e+20
Mxy 4.09e+19
Mxz -4.20e+19
Myy -1.44e+19
Myz -7.27e+19
Mzz -1.32e+20
##############
######################
############################
##############################
############-------------#########
-#######-----------------------#####
---###-----------------------------###
--------------------------------------##
---##----------------------------------#
---#####------------------ -------------
--#######----------------- P -------------
-##########--------------- -------------
############------------------------------
##############--------------------------
################------------------------
##################--------------------
#####################---------------
##########################--------
##############################
####### ##################
#### T ###############
###########
Global CMT Convention Moment Tensor:
R T P
-1.32e+20 -4.20e+19 7.27e+19
-4.20e+19 1.46e+20 -4.09e+19
7.27e+19 -4.09e+19 -1.44e+19
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090715005806/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 0.5 330 40 -70 2.51 0.2246
WVFGRD96 1.0 135 80 -75 2.66 0.2337
WVFGRD96 2.0 125 75 -75 2.73 0.3013
WVFGRD96 3.0 125 65 -70 2.73 0.3705
WVFGRD96 4.0 125 60 -65 2.75 0.4080
WVFGRD96 5.0 120 60 -70 2.83 0.3934
WVFGRD96 6.0 125 60 -65 2.82 0.3771
WVFGRD96 7.0 130 60 -60 2.80 0.3431
WVFGRD96 8.0 165 65 -65 2.78 0.3175
WVFGRD96 9.0 175 70 -60 2.79 0.2954
WVFGRD96 10.0 175 70 -60 2.80 0.2769
WVFGRD96 11.0 175 70 -55 2.80 0.2571
WVFGRD96 12.0 180 65 -55 2.83 0.2481
WVFGRD96 13.0 180 65 -50 2.83 0.2370
WVFGRD96 14.0 350 65 60 2.77 0.2298
WVFGRD96 15.0 315 50 80 2.80 0.2369
WVFGRD96 16.0 315 55 80 2.80 0.2419
WVFGRD96 17.0 315 55 80 2.81 0.2459
WVFGRD96 18.0 345 60 55 2.86 0.2407
WVFGRD96 19.0 310 55 80 2.83 0.2419
WVFGRD96 20.0 310 60 80 2.83 0.2378
WVFGRD96 21.0 300 55 60 2.87 0.2373
WVFGRD96 22.0 300 55 50 2.90 0.2407
WVFGRD96 23.0 300 55 50 2.91 0.2416
WVFGRD96 24.0 305 50 50 2.93 0.2493
WVFGRD96 25.0 305 50 50 2.94 0.2582
WVFGRD96 26.0 310 50 55 2.95 0.2684
WVFGRD96 27.0 310 50 55 2.96 0.2771
WVFGRD96 28.0 310 50 55 2.97 0.2827
WVFGRD96 29.0 310 50 60 2.97 0.2836
The best solution is
WVFGRD96 4.0 125 60 -65 2.75 0.4080
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 Jul 14 21:18:25 CDT 2009