2009/04/06 09:47:02 42.264 13.393 10.0 3.00 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/06 09:47:02:0 42.26 13.39 10.0 3.0 Italy
Stations used:
IV.ASSB IV.CERA IV.CING IV.FAGN IV.FDMO IV.MGAB IV.MNS
IV.MTCE IV.MURB 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 = 7.67e+20 dyne-cm
Mw = 3.19
Z = 4 km
Plane Strike Dip Rake
NP1 117 78 112
NP2 235 25 30
Principal Axes:
Axis Value Plunge Azimuth
T 7.67e+20 52 53
N 0.00e+00 21 292
P -7.67e+20 29 190
Moment Tensor: (dyne-cm)
Component Value
Mxx -4.61e+20
Mxy 4.20e+19
Mxz 5.47e+20
Myy 1.67e+20
Myz 3.52e+20
Mzz 2.94e+20
--------------
----------------------
----------###############---
-------######################-
-------###########################
------##############################
##---##################### #########
########################### T ##########
####---#################### ##########
####------################################
###----------#############################
###-------------##########################
###-----------------######################
##--------------------##################
##-------------------------#############
#------------------------------#######
------------------------------------
------------- ------------------
----------- P ----------------
---------- ---------------
----------------------
--------------
Global CMT Convention Moment Tensor:
R T P
2.94e+20 5.47e+20 -3.52e+20
5.47e+20 -4.61e+20 -4.20e+19
-3.52e+20 -4.20e+19 1.67e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090406094702/index.html
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STK = 235
DIP = 25
RAKE = 30
MW = 3.19
HS = 4.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/06 09:47:02:0 42.26 13.39 10.0 3.0 Italy
Stations used:
IV.ASSB IV.CERA IV.CING IV.FAGN IV.FDMO IV.MGAB IV.MNS
IV.MTCE IV.MURB 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 = 7.67e+20 dyne-cm
Mw = 3.19
Z = 4 km
Plane Strike Dip Rake
NP1 117 78 112
NP2 235 25 30
Principal Axes:
Axis Value Plunge Azimuth
T 7.67e+20 52 53
N 0.00e+00 21 292
P -7.67e+20 29 190
Moment Tensor: (dyne-cm)
Component Value
Mxx -4.61e+20
Mxy 4.20e+19
Mxz 5.47e+20
Myy 1.67e+20
Myz 3.52e+20
Mzz 2.94e+20
--------------
----------------------
----------###############---
-------######################-
-------###########################
------##############################
##---##################### #########
########################### T ##########
####---#################### ##########
####------################################
###----------#############################
###-------------##########################
###-----------------######################
##--------------------##################
##-------------------------#############
#------------------------------#######
------------------------------------
------------- ------------------
----------- P ----------------
---------- ---------------
----------------------
--------------
Global CMT Convention Moment Tensor:
R T P
2.94e+20 5.47e+20 -3.52e+20
5.47e+20 -4.61e+20 -4.20e+19
-3.52e+20 -4.20e+19 1.67e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090406094702/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 85 75 70 3.19 0.4413
WVFGRD96 1.0 270 30 60 3.16 0.4710
WVFGRD96 2.0 95 60 75 3.20 0.4910
WVFGRD96 3.0 235 20 25 3.21 0.5111
WVFGRD96 4.0 235 25 30 3.19 0.5200
WVFGRD96 5.0 250 20 45 3.29 0.5150
WVFGRD96 6.0 220 30 15 3.28 0.4909
WVFGRD96 7.0 215 30 5 3.28 0.4623
WVFGRD96 8.0 210 40 -10 3.25 0.4366
WVFGRD96 9.0 205 35 -15 3.25 0.4095
WVFGRD96 10.0 220 40 -20 3.27 0.3859
WVFGRD96 11.0 215 40 -25 3.28 0.3608
WVFGRD96 12.0 220 45 -30 3.29 0.3387
WVFGRD96 13.0 220 45 -30 3.29 0.3174
WVFGRD96 14.0 215 45 -35 3.30 0.2972
WVFGRD96 15.0 175 35 -40 3.31 0.2708
WVFGRD96 16.0 170 35 -40 3.32 0.2548
WVFGRD96 17.0 165 35 -45 3.33 0.2413
WVFGRD96 18.0 165 35 -45 3.33 0.2286
WVFGRD96 19.0 160 35 -50 3.34 0.2164
WVFGRD96 20.0 155 35 -50 3.35 0.2062
WVFGRD96 21.0 155 35 -50 3.35 0.1962
WVFGRD96 22.0 240 30 25 3.39 0.1872
WVFGRD96 23.0 245 30 35 3.40 0.1906
WVFGRD96 24.0 245 30 35 3.41 0.1953
WVFGRD96 25.0 245 30 35 3.42 0.2007
WVFGRD96 26.0 245 30 35 3.43 0.2028
WVFGRD96 27.0 245 30 35 3.44 0.2074
WVFGRD96 28.0 245 25 35 3.45 0.2139
WVFGRD96 29.0 240 30 30 3.46 0.2184
The best solution is
WVFGRD96 4.0 235 25 30 3.19 0.5200
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=Fri May 1 20:17:17 CDT 2009