2009/04/24 22:51:29 42.267 13.508 11.0 3.0 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/24 22:51:29:0 42.27 13.51 11.0 3.0 Italy
Stations used:
IV.FDMO IV.FIAM IV.GUMA IV.LPEL 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 = 6.46e+20 dyne-cm
Mw = 3.14
Z = 7 km
Plane Strike Dip Rake
NP1 165 65 -40
NP2 275 54 -149
Principal Axes:
Axis Value Plunge Azimuth
T 6.46e+20 6 222
N 0.00e+00 44 318
P -6.46e+20 45 125
Moment Tensor: (dyne-cm)
Component Value
Mxx 2.45e+20
Mxy 4.68e+20
Mxz 1.33e+20
Myy 7.25e+19
Myz -3.12e+20
Mzz -3.18e+20
-#############
-----#################
-------#####################
--------######################
---------#########################
----------##########################
----------#-------------##############
------######-------------------#########
---##########---------------------######
-#############------------------------####
##############--------------------------##
###############--------------------------#
###############---------------------------
###############------------- ---------
###############------------- P ---------
###############------------ --------
###############---------------------
## ##########-------------------
T ###########----------------
#############-------------
#############---------
###########---
Global CMT Convention Moment Tensor:
R T P
-3.18e+20 1.33e+20 3.12e+20
1.33e+20 2.45e+20 -4.68e+20
3.12e+20 -4.68e+20 7.25e+19
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090424225129/index.html
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STK = 165
DIP = 65
RAKE = -40
MW = 3.14
HS = 7.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/24 22:51:29:0 42.27 13.51 11.0 3.0 Italy
Stations used:
IV.FDMO IV.FIAM IV.GUMA IV.LPEL 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 = 6.46e+20 dyne-cm
Mw = 3.14
Z = 7 km
Plane Strike Dip Rake
NP1 165 65 -40
NP2 275 54 -149
Principal Axes:
Axis Value Plunge Azimuth
T 6.46e+20 6 222
N 0.00e+00 44 318
P -6.46e+20 45 125
Moment Tensor: (dyne-cm)
Component Value
Mxx 2.45e+20
Mxy 4.68e+20
Mxz 1.33e+20
Myy 7.25e+19
Myz -3.12e+20
Mzz -3.18e+20
-#############
-----#################
-------#####################
--------######################
---------#########################
----------##########################
----------#-------------##############
------######-------------------#########
---##########---------------------######
-#############------------------------####
##############--------------------------##
###############--------------------------#
###############---------------------------
###############------------- ---------
###############------------- P ---------
###############------------ --------
###############---------------------
## ##########-------------------
T ###########----------------
#############-------------
#############---------
###########---
Global CMT Convention Moment Tensor:
R T P
-3.18e+20 1.33e+20 3.12e+20
1.33e+20 2.45e+20 -4.68e+20
3.12e+20 -4.68e+20 7.25e+19
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090424225129/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 25 2.99 0.5175
WVFGRD96 1.0 15 70 60 2.96 0.5392
WVFGRD96 2.0 15 70 65 3.03 0.5946
WVFGRD96 3.0 20 80 60 3.03 0.6371
WVFGRD96 4.0 165 60 -35 3.05 0.7060
WVFGRD96 5.0 165 60 -35 3.11 0.7192
WVFGRD96 6.0 165 60 -35 3.12 0.7434
WVFGRD96 7.0 165 65 -40 3.14 0.7459
WVFGRD96 8.0 165 65 -35 3.12 0.7392
WVFGRD96 9.0 170 70 -30 3.13 0.7295
WVFGRD96 10.0 170 70 -30 3.14 0.7121
WVFGRD96 11.0 170 70 -30 3.15 0.6973
WVFGRD96 12.0 170 65 -35 3.16 0.6798
WVFGRD96 13.0 170 65 -35 3.17 0.6627
WVFGRD96 14.0 170 65 -35 3.18 0.6434
WVFGRD96 15.0 165 60 -40 3.21 0.6237
WVFGRD96 16.0 165 55 -45 3.23 0.6066
WVFGRD96 17.0 165 55 -45 3.24 0.5878
WVFGRD96 18.0 165 55 -45 3.24 0.5683
WVFGRD96 19.0 165 45 -50 3.26 0.5534
WVFGRD96 20.0 165 45 -50 3.27 0.5397
WVFGRD96 21.0 160 45 -60 3.28 0.5262
WVFGRD96 22.0 160 45 -60 3.29 0.5145
WVFGRD96 23.0 145 40 -80 3.31 0.5020
WVFGRD96 24.0 145 40 -85 3.32 0.4964
WVFGRD96 25.0 140 40 -90 3.33 0.4872
WVFGRD96 26.0 320 50 -90 3.34 0.4748
WVFGRD96 27.0 315 50 -95 3.34 0.4621
WVFGRD96 28.0 185 35 35 3.32 0.4481
WVFGRD96 29.0 185 35 35 3.33 0.4533
The best solution is
WVFGRD96 7.0 165 65 -40 3.14 0.7459
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=Wed Sep 2 07:57:48 CDT 2009