2009/04/26 17:56:06 42.456 13.378 10.6 3.30 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/26 17:56:06:0 42.46 13.38 10.6 3.3 Italy
Stations used:
IV.ASSB IV.CERT IV.FDMO IV.FIAM IV.LPEL IV.MNS IV.MTCE
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 = 3.13e+20 dyne-cm
Mw = 2.93
Z = 8 km
Plane Strike Dip Rake
NP1 108 56 -113
NP2 325 40 -60
Principal Axes:
Axis Value Plunge Azimuth
T 3.13e+20 9 214
N 0.00e+00 19 121
P -3.13e+20 69 327
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.82e+20
Mxy 1.60e+20
Mxz -1.25e+20
Myy 8.45e+19
Myz 3.02e+19
Mzz -2.67e+20
##############
######################
--------------##############
------------------############
-----------------------###########
--------------------------##########
----------------------------##########
---------------- ------------#########
#--------------- P -------------########
###-------------- --------------########
####------------------------------########
######-----------------------------#######
########---------------------------#######
##########-------------------------#####
#############----------------------#####
#################-----------------#---
################################----
###############################---
### ######################--
## T ######################-
####################
##############
Global CMT Convention Moment Tensor:
R T P
-2.67e+20 -1.25e+20 -3.02e+19
-1.25e+20 1.82e+20 -1.60e+20
-3.02e+19 -1.60e+20 8.45e+19
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090426175606/index.html
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STK = 325
DIP = 40
RAKE = -60
MW = 2.93
HS = 8.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/26 17:56:06:0 42.46 13.38 10.6 3.3 Italy
Stations used:
IV.ASSB IV.CERT IV.FDMO IV.FIAM IV.LPEL IV.MNS IV.MTCE
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 = 3.13e+20 dyne-cm
Mw = 2.93
Z = 8 km
Plane Strike Dip Rake
NP1 108 56 -113
NP2 325 40 -60
Principal Axes:
Axis Value Plunge Azimuth
T 3.13e+20 9 214
N 0.00e+00 19 121
P -3.13e+20 69 327
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.82e+20
Mxy 1.60e+20
Mxz -1.25e+20
Myy 8.45e+19
Myz 3.02e+19
Mzz -2.67e+20
##############
######################
--------------##############
------------------############
-----------------------###########
--------------------------##########
----------------------------##########
---------------- ------------#########
#--------------- P -------------########
###-------------- --------------########
####------------------------------########
######-----------------------------#######
########---------------------------#######
##########-------------------------#####
#############----------------------#####
#################-----------------#---
################################----
###############################---
### ######################--
## T ######################-
####################
##############
Global CMT Convention Moment Tensor:
R T P
-2.67e+20 -1.25e+20 -3.02e+19
-1.25e+20 1.82e+20 -1.60e+20
-3.02e+19 -1.60e+20 8.45e+19
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090426175606/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 0.5 280 40 90 2.65 0.2448
WVFGRD96 1.0 110 50 -90 2.70 0.2295
WVFGRD96 2.0 0 20 -15 2.82 0.2482
WVFGRD96 3.0 355 25 -20 2.80 0.3158
WVFGRD96 4.0 350 30 -30 2.79 0.3576
WVFGRD96 5.0 335 25 -45 2.91 0.3957
WVFGRD96 6.0 330 35 -60 2.94 0.4346
WVFGRD96 7.0 330 40 -60 2.95 0.4694
WVFGRD96 8.0 325 40 -60 2.93 0.4796
WVFGRD96 9.0 330 45 -55 2.93 0.4781
WVFGRD96 10.0 330 45 -55 2.94 0.4708
WVFGRD96 11.0 330 45 -55 2.94 0.4578
WVFGRD96 12.0 330 45 -55 2.95 0.4430
WVFGRD96 13.0 340 50 -35 2.96 0.4260
WVFGRD96 14.0 350 55 -30 2.98 0.4089
WVFGRD96 15.0 350 55 -30 3.01 0.3975
WVFGRD96 16.0 350 55 -30 3.02 0.3837
WVFGRD96 17.0 -10 55 -30 3.03 0.3696
WVFGRD96 18.0 -5 60 -25 3.05 0.3572
WVFGRD96 19.0 -5 60 -25 3.06 0.3462
WVFGRD96 20.0 -5 60 -25 3.07 0.3366
WVFGRD96 21.0 -5 60 -25 3.08 0.3281
WVFGRD96 22.0 355 60 -25 3.09 0.3192
WVFGRD96 23.0 355 60 -25 3.10 0.3107
WVFGRD96 24.0 355 60 -20 3.11 0.3022
WVFGRD96 25.0 355 60 -15 3.12 0.2952
WVFGRD96 26.0 -5 60 -15 3.13 0.2898
WVFGRD96 27.0 -5 60 -15 3.14 0.2842
WVFGRD96 28.0 -5 60 -10 3.16 0.2788
WVFGRD96 29.0 355 65 -10 3.18 0.2732
The best solution is
WVFGRD96 8.0 325 40 -60 2.93 0.4796
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 Apr 27 16:12:30 CDT 2009