2009/04/10 19:18:39 42.344 13.358 10.2 3.00 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/10 19:18:39:0 42.34 13.36 10.2 3.0 Italy
Stations used:
IV.ARVD IV.CERT IV.CESI IV.CESX IV.CING IV.FDMO IV.FIAM
IV.GUAR IV.LPEL IV.MIDA IV.MNS IV.MTCE IV.NRCA IV.OFFI
IV.RMP IV.TERO IV.TRTR
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 5.62e+20 dyne-cm
Mw = 3.10
Z = 9 km
Plane Strike Dip Rake
NP1 118 58 -116
NP2 340 40 -55
Principal Axes:
Axis Value Plunge Azimuth
T 5.62e+20 10 226
N 0.00e+00 22 132
P -5.62e+20 66 338
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.86e+20
Mxy 3.05e+20
Mxz -2.60e+20
Myy 2.67e+20
Myz 9.34e+18
Mzz -4.54e+20
-#############
-----------###########
-----------------###########
--------------------##########
------------------------##########
---------------------------#########
#-------------- -----------#########
###------------- P ------------#########
###------------- -------------########
######---------------------------#########
#######---------------------------########
#########-------------------------########
###########-----------------------########
############---------------------#######
###############------------------#######
##################--------------######
######################---------####-
## ########################-----
T #######################----
######################----
####################--
##############
Global CMT Convention Moment Tensor:
R T P
-4.54e+20 -2.60e+20 -9.34e+18
-2.60e+20 1.86e+20 -3.05e+20
-9.34e+18 -3.05e+20 2.67e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090410191839/index.html
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STK = 340
DIP = 40
RAKE = -55
MW = 3.10
HS = 9.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/10 19:18:39:0 42.34 13.36 10.2 3.0 Italy
Stations used:
IV.ARVD IV.CERT IV.CESI IV.CESX IV.CING IV.FDMO IV.FIAM
IV.GUAR IV.LPEL IV.MIDA IV.MNS IV.MTCE IV.NRCA IV.OFFI
IV.RMP IV.TERO IV.TRTR
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 5.62e+20 dyne-cm
Mw = 3.10
Z = 9 km
Plane Strike Dip Rake
NP1 118 58 -116
NP2 340 40 -55
Principal Axes:
Axis Value Plunge Azimuth
T 5.62e+20 10 226
N 0.00e+00 22 132
P -5.62e+20 66 338
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.86e+20
Mxy 3.05e+20
Mxz -2.60e+20
Myy 2.67e+20
Myz 9.34e+18
Mzz -4.54e+20
-#############
-----------###########
-----------------###########
--------------------##########
------------------------##########
---------------------------#########
#-------------- -----------#########
###------------- P ------------#########
###------------- -------------########
######---------------------------#########
#######---------------------------########
#########-------------------------########
###########-----------------------########
############---------------------#######
###############------------------#######
##################--------------######
######################---------####-
## ########################-----
T #######################----
######################----
####################--
##############
Global CMT Convention Moment Tensor:
R T P
-4.54e+20 -2.60e+20 -9.34e+18
-2.60e+20 1.86e+20 -3.05e+20
-9.34e+18 -3.05e+20 2.67e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090410191839/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 0.5 130 50 -90 2.84 0.2721
WVFGRD96 1.0 305 45 -95 2.88 0.2422
WVFGRD96 2.0 335 20 -60 3.01 0.2426
WVFGRD96 3.0 355 25 -30 2.99 0.2904
WVFGRD96 4.0 345 25 -45 2.99 0.3314
WVFGRD96 5.0 340 25 -55 3.10 0.3636
WVFGRD96 6.0 345 30 -50 3.10 0.3855
WVFGRD96 7.0 335 35 -60 3.11 0.4079
WVFGRD96 8.0 340 40 -55 3.09 0.4307
WVFGRD96 9.0 340 40 -55 3.10 0.4396
WVFGRD96 10.0 340 40 -55 3.10 0.4392
WVFGRD96 11.0 345 45 -50 3.11 0.4310
WVFGRD96 12.0 335 45 -65 3.12 0.4197
WVFGRD96 13.0 340 50 -55 3.13 0.4069
WVFGRD96 14.0 340 50 -55 3.14 0.3923
WVFGRD96 15.0 340 50 -55 3.18 0.3843
WVFGRD96 16.0 340 55 -55 3.18 0.3722
WVFGRD96 17.0 15 35 -20 3.19 0.3595
WVFGRD96 18.0 15 35 -20 3.20 0.3481
WVFGRD96 19.0 20 35 -10 3.20 0.3369
WVFGRD96 20.0 175 30 -45 3.19 0.3253
WVFGRD96 21.0 175 35 -45 3.21 0.3173
WVFGRD96 22.0 165 30 -60 3.21 0.3090
WVFGRD96 23.0 160 30 -65 3.22 0.2999
WVFGRD96 24.0 155 30 -70 3.23 0.2905
WVFGRD96 25.0 -5 50 -35 3.25 0.2847
WVFGRD96 26.0 -5 50 -35 3.25 0.2796
WVFGRD96 27.0 -5 50 -35 3.26 0.2730
WVFGRD96 28.0 0 45 -30 3.26 0.2695
WVFGRD96 29.0 0 45 -30 3.27 0.2673
The best solution is
WVFGRD96 9.0 340 40 -55 3.10 0.4396
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=Thu Apr 30 14:59:16 CDT 2009