2009/04/14 17:27:30 42.527 13.295 3.6 3.50 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/14 17:27:30:0 42.53 13.30 3.6 3.5 Italy
Stations used:
IV.CERT IV.CESI IV.CING IV.FAGN IV.FDMO IV.FIAM IV.GUAR
IV.INTR IV.LPEL IV.MNS IV.MTCE IV.NRCA IV.OFFI IV.PIEI
IV.RDP IV.RMP IV.SACS IV.TOLF IV.TRTR IV.VVLD MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 5.31e+21 dyne-cm
Mw = 3.75
Z = 6 km
Plane Strike Dip Rake
NP1 137 51 -98
NP2 330 40 -80
Principal Axes:
Axis Value Plunge Azimuth
T 5.31e+21 5 233
N 0.00e+00 6 142
P -5.31e+21 82 3
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.80e+21
Mxy 2.53e+21
Mxz -1.07e+21
Myy 3.35e+21
Myz -4.33e+20
Mzz -5.15e+21
##############
-------###############
---------------#############
#------------------###########
##---------------------###########
###-----------------------##########
####------------------------##########
######-------------------------#########
######------------- ----------########
########------------ P ----------#########
#########----------- -----------########
##########-------------------------#######
###########------------------------#######
###########-----------------------######
#############---------------------######
#############--------------------#####
# ###########-----------------####
T #############--------------####
#################----------##
##########################--
######################
##############
Global CMT Convention Moment Tensor:
R T P
-5.15e+21 -1.07e+21 4.33e+20
-1.07e+21 1.80e+21 -2.53e+21
4.33e+20 -2.53e+21 3.35e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090414172730/index.html
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STK = 330
DIP = 40
RAKE = -80
MW = 3.75
HS = 6.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/14 17:27:30:0 42.53 13.30 3.6 3.5 Italy
Stations used:
IV.CERT IV.CESI IV.CING IV.FAGN IV.FDMO IV.FIAM IV.GUAR
IV.INTR IV.LPEL IV.MNS IV.MTCE IV.NRCA IV.OFFI IV.PIEI
IV.RDP IV.RMP IV.SACS IV.TOLF IV.TRTR IV.VVLD MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 5.31e+21 dyne-cm
Mw = 3.75
Z = 6 km
Plane Strike Dip Rake
NP1 137 51 -98
NP2 330 40 -80
Principal Axes:
Axis Value Plunge Azimuth
T 5.31e+21 5 233
N 0.00e+00 6 142
P -5.31e+21 82 3
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.80e+21
Mxy 2.53e+21
Mxz -1.07e+21
Myy 3.35e+21
Myz -4.33e+20
Mzz -5.15e+21
##############
-------###############
---------------#############
#------------------###########
##---------------------###########
###-----------------------##########
####------------------------##########
######-------------------------#########
######------------- ----------########
########------------ P ----------#########
#########----------- -----------########
##########-------------------------#######
###########------------------------#######
###########-----------------------######
#############---------------------######
#############--------------------#####
# ###########-----------------####
T #############--------------####
#################----------##
##########################--
######################
##############
Global CMT Convention Moment Tensor:
R T P
-5.15e+21 -1.07e+21 4.33e+20
-1.07e+21 1.80e+21 -2.53e+21
4.33e+20 -2.53e+21 3.35e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090414172730/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 0 40 -25 3.46 0.3015
WVFGRD96 1.0 0 40 -25 3.47 0.3088
WVFGRD96 2.0 0 30 -25 3.56 0.3467
WVFGRD96 3.0 -5 35 -40 3.58 0.3994
WVFGRD96 4.0 345 40 -60 3.63 0.4492
WVFGRD96 5.0 335 35 -70 3.72 0.4922
WVFGRD96 6.0 330 40 -80 3.75 0.5475
WVFGRD96 7.0 330 40 -80 3.74 0.5467
WVFGRD96 8.0 335 45 -75 3.70 0.5062
WVFGRD96 9.0 335 45 -75 3.69 0.4750
WVFGRD96 10.0 340 50 -65 3.68 0.4435
WVFGRD96 11.0 340 50 -65 3.68 0.4165
WVFGRD96 12.0 345 50 -60 3.68 0.3905
WVFGRD96 13.0 350 55 -50 3.67 0.3655
WVFGRD96 14.0 350 60 -50 3.68 0.3420
WVFGRD96 15.0 350 60 -55 3.71 0.3333
WVFGRD96 16.0 180 50 -35 3.72 0.3203
WVFGRD96 17.0 180 50 -30 3.72 0.3071
WVFGRD96 18.0 180 50 -30 3.73 0.2936
WVFGRD96 19.0 185 50 -20 3.73 0.2804
WVFGRD96 20.0 5 75 -15 3.72 0.2697
WVFGRD96 21.0 190 75 25 3.74 0.2613
WVFGRD96 22.0 190 75 20 3.74 0.2575
WVFGRD96 23.0 190 75 20 3.75 0.2542
WVFGRD96 24.0 190 75 20 3.76 0.2524
WVFGRD96 25.0 190 75 20 3.77 0.2506
WVFGRD96 26.0 190 80 20 3.78 0.2510
WVFGRD96 27.0 190 80 20 3.79 0.2512
WVFGRD96 28.0 190 80 20 3.81 0.2517
WVFGRD96 29.0 190 80 20 3.83 0.2532
The best solution is
WVFGRD96 6.0 330 40 -80 3.75 0.5475
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 20 11:54:10 CDT 2009