2009/04/13 08:41:08 42.271 13.505 9.9 3.00 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/13 08:41:08:0 42.27 13.51 9.9 3.0 Italy
Stations used:
IV.CERT IV.CESX IV.CING IV.FDMO IV.FIAM IV.GIUL IV.LNSS
IV.LPEL IV.MGAB IV.MIDA IV.MTCE IV.NRCA IV.POFI MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 7.16e+20 dyne-cm
Mw = 3.17
Z = 7 km
Plane Strike Dip Rake
NP1 170 65 -35
NP2 276 59 -150
Principal Axes:
Axis Value Plunge Azimuth
T 7.16e+20 4 224
N 0.00e+00 48 319
P -7.16e+20 42 131
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.91e+20
Mxy 5.53e+20
Mxz 1.98e+20
Myy 1.23e+20
Myz -3.03e+20
Mzz -3.15e+20
---###########
------################
--------####################
---------#####################
----------########################
-----------#########################
------------##########################
------#######---------------############
--###########-------------------########
-#############----------------------######
##############-------------------------###
###############--------------------------#
###############---------------------------
###############-------------------------
###############------------- ---------
###############------------ P --------
##############------------ -------
# ##########--------------------
T ###########-----------------
############---------------
############----------
#########-----
Global CMT Convention Moment Tensor:
R T P
-3.15e+20 1.98e+20 3.03e+20
1.98e+20 1.91e+20 -5.53e+20
3.03e+20 -5.53e+20 1.23e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090413084108/index.html
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STK = 170
DIP = 65
RAKE = -35
MW = 3.17
HS = 7.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/13 08:41:08:0 42.27 13.51 9.9 3.0 Italy
Stations used:
IV.CERT IV.CESX IV.CING IV.FDMO IV.FIAM IV.GIUL IV.LNSS
IV.LPEL IV.MGAB IV.MIDA IV.MTCE IV.NRCA IV.POFI MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 7.16e+20 dyne-cm
Mw = 3.17
Z = 7 km
Plane Strike Dip Rake
NP1 170 65 -35
NP2 276 59 -150
Principal Axes:
Axis Value Plunge Azimuth
T 7.16e+20 4 224
N 0.00e+00 48 319
P -7.16e+20 42 131
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.91e+20
Mxy 5.53e+20
Mxz 1.98e+20
Myy 1.23e+20
Myz -3.03e+20
Mzz -3.15e+20
---###########
------################
--------####################
---------#####################
----------########################
-----------#########################
------------##########################
------#######---------------############
--###########-------------------########
-#############----------------------######
##############-------------------------###
###############--------------------------#
###############---------------------------
###############-------------------------
###############------------- ---------
###############------------ P --------
##############------------ -------
# ##########--------------------
T ###########-----------------
############---------------
############----------
#########-----
Global CMT Convention Moment Tensor:
R T P
-3.15e+20 1.98e+20 3.03e+20
1.98e+20 1.91e+20 -5.53e+20
3.03e+20 -5.53e+20 1.23e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090413084108/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 0.5 185 30 15 3.02 0.4132
WVFGRD96 1.0 190 35 30 2.99 0.4391
WVFGRD96 2.0 190 35 30 3.06 0.4956
WVFGRD96 3.0 185 85 -40 3.05 0.5220
WVFGRD96 4.0 175 70 -30 3.07 0.5621
WVFGRD96 5.0 170 65 -40 3.15 0.5761
WVFGRD96 6.0 170 65 -35 3.15 0.5951
WVFGRD96 7.0 170 65 -35 3.17 0.6010
WVFGRD96 8.0 175 70 -30 3.15 0.5959
WVFGRD96 9.0 175 70 -30 3.16 0.5859
WVFGRD96 10.0 175 70 -25 3.17 0.5747
WVFGRD96 11.0 175 70 -30 3.18 0.5596
WVFGRD96 12.0 175 70 -30 3.20 0.5453
WVFGRD96 13.0 170 65 -30 3.21 0.5286
WVFGRD96 14.0 170 65 -35 3.22 0.5123
WVFGRD96 15.0 170 65 -35 3.25 0.4998
WVFGRD96 16.0 165 60 -40 3.26 0.4835
WVFGRD96 17.0 165 60 -40 3.27 0.4679
WVFGRD96 18.0 165 60 -40 3.28 0.4528
WVFGRD96 19.0 165 60 -40 3.29 0.4380
WVFGRD96 20.0 165 60 -40 3.30 0.4239
WVFGRD96 21.0 165 60 -40 3.31 0.4098
WVFGRD96 22.0 165 60 -45 3.31 0.3971
WVFGRD96 23.0 160 55 -50 3.32 0.3848
WVFGRD96 24.0 160 55 -50 3.33 0.3736
WVFGRD96 25.0 160 55 -50 3.33 0.3618
WVFGRD96 26.0 160 55 -50 3.34 0.3516
WVFGRD96 27.0 175 70 -30 3.34 0.3416
WVFGRD96 28.0 180 80 -25 3.36 0.3390
WVFGRD96 29.0 180 80 -25 3.37 0.3380
The best solution is
WVFGRD96 7.0 170 65 -35 3.17 0.6010
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 14:38:40 CDT 2009