2009/05/02 20:15:00 42.291 13.492 8.8 3.2 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/05/02 20:15:00:7 42.29 13.49 8.8 3.2 Italy
Stations used:
IV.CERT IV.FIAM IV.GUAR IV.GUMA IV.OFFI IV.RMP 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 = 1 km
Plane Strike Dip Rake
NP1 301 76 164
NP2 35 75 15
Principal Axes:
Axis Value Plunge Azimuth
T 6.03e+20 21 258
N 0.00e+00 69 79
P -6.03e+20 0 348
Moment Tensor: (dyne-cm)
Component Value
Mxx -5.54e+20
Mxy 2.29e+20
Mxz -4.59e+19
Myy 4.76e+20
Myz -1.97e+20
Mzz 7.80e+19
- P ----------
----- --------------
--------------------------##
--------------------------####
----------------------------######
####------------------------########
###########-----------------##########
################------------############
###################--------#############
########################---###############
##########################################
### ###################----#############
### T ##################-------###########
## ################------------#######
####################--------------######
#################------------------###
###############--------------------#
############----------------------
########----------------------
####------------------------
----------------------
--------------
Global CMT Convention Moment Tensor:
R T P
7.80e+19 -4.59e+19 1.97e+20
-4.59e+19 -5.54e+20 -2.29e+20
1.97e+20 -2.29e+20 4.76e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090502201500/index.html
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STK = 35
DIP = 75
RAKE = 15
MW = 3.12
HS = 1.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/05/02 20:15:00:7 42.29 13.49 8.8 3.2 Italy
Stations used:
IV.CERT IV.FIAM IV.GUAR IV.GUMA IV.OFFI IV.RMP 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 = 1 km
Plane Strike Dip Rake
NP1 301 76 164
NP2 35 75 15
Principal Axes:
Axis Value Plunge Azimuth
T 6.03e+20 21 258
N 0.00e+00 69 79
P -6.03e+20 0 348
Moment Tensor: (dyne-cm)
Component Value
Mxx -5.54e+20
Mxy 2.29e+20
Mxz -4.59e+19
Myy 4.76e+20
Myz -1.97e+20
Mzz 7.80e+19
- P ----------
----- --------------
--------------------------##
--------------------------####
----------------------------######
####------------------------########
###########-----------------##########
################------------############
###################--------#############
########################---###############
##########################################
### ###################----#############
### T ##################-------###########
## ################------------#######
####################--------------######
#################------------------###
###############--------------------#
############----------------------
########----------------------
####------------------------
----------------------
--------------
Global CMT Convention Moment Tensor:
R T P
7.80e+19 -4.59e+19 1.97e+20
-4.59e+19 -5.54e+20 -2.29e+20
1.97e+20 -2.29e+20 4.76e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090502201500/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 1.0 35 75 15 3.12 0.5585
WVFGRD96 2.0 210 80 0 3.17 0.5522
WVFGRD96 3.0 210 80 5 3.21 0.5330
WVFGRD96 4.0 210 80 0 3.25 0.5074
WVFGRD96 5.0 210 75 -5 3.28 0.4815
WVFGRD96 6.0 30 70 5 3.33 0.4613
WVFGRD96 7.0 30 75 5 3.34 0.4466
WVFGRD96 8.0 30 80 5 3.35 0.4311
WVFGRD96 9.0 30 80 5 3.36 0.4142
WVFGRD96 10.0 30 80 5 3.37 0.3975
WVFGRD96 11.0 210 80 -5 3.36 0.3847
WVFGRD96 12.0 210 80 -5 3.38 0.3756
WVFGRD96 13.0 210 80 -5 3.39 0.3650
WVFGRD96 14.0 210 75 -5 3.39 0.3541
WVFGRD96 15.0 210 75 -5 3.41 0.3443
WVFGRD96 16.0 210 75 -5 3.42 0.3348
WVFGRD96 17.0 210 70 0 3.43 0.3265
WVFGRD96 18.0 210 70 0 3.43 0.3197
WVFGRD96 19.0 210 70 0 3.44 0.3133
WVFGRD96 20.0 205 70 0 3.46 0.3072
WVFGRD96 21.0 210 65 0 3.45 0.3016
WVFGRD96 22.0 215 80 25 3.47 0.2991
WVFGRD96 23.0 215 75 25 3.47 0.2967
WVFGRD96 24.0 210 70 15 3.48 0.2951
WVFGRD96 25.0 210 70 15 3.49 0.2935
WVFGRD96 26.0 210 70 15 3.50 0.2927
WVFGRD96 27.0 210 70 15 3.51 0.2922
WVFGRD96 28.0 210 65 10 3.52 0.2935
WVFGRD96 29.0 210 70 10 3.54 0.2946
The best solution is
WVFGRD96 1.0 35 75 15 3.12 0.5585
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 May 17 12:22:52 CDT 2010