2009/10/20 05:07:30 42.398 13.24 9.9 3.5 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/10/20 05:07:30:0 42.40 13.24 9.9 3.5 Italy
Stations used:
IV.CAMP IV.CESI IV.CESX IV.FAGN IV.FIAM IV.GUAR IV.GUMA
IV.INTR IV.LNSS IV.LPEL IV.MIDA IV.MTCE IV.OFFI IV.POFI
IV.RDP IV.RMP IV.RNI2 IV.SACS IV.TERO IV.TOLF MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 2.66e+21 dyne-cm
Mw = 3.55
Z = 2 km
Plane Strike Dip Rake
NP1 10 70 -60
NP2 131 36 -144
Principal Axes:
Axis Value Plunge Azimuth
T 2.66e+21 19 78
N 0.00e+00 28 179
P -2.66e+21 55 318
Moment Tensor: (dyne-cm)
Component Value
Mxx -3.83e+20
Mxy 9.21e+20
Mxz -7.55e+20
Myy 1.86e+21
Myz 1.66e+21
Mzz -1.48e+21
-----------###
----------------######
-------------------#########
--------------------##########
#----------------------###########
#-----------------------############
##---------- ----------#############
###---------- P ----------##############
###---------- ----------######### ##
####-----------------------######### T ###
#####---------------------########## ###
######--------------------################
######--------------------################
######------------------################
########----------------################
########--------------################
#########------------###############
###########--------###############
############----##############
##############---######-----
##########------------
####----------
Global CMT Convention Moment Tensor:
R T P
-1.48e+21 -7.55e+20 -1.66e+21
-7.55e+20 -3.83e+20 -9.21e+20
-1.66e+21 -9.21e+20 1.86e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20091020050730/index.html
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STK = 10
DIP = 70
RAKE = -60
MW = 3.55
HS = 2.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/10/20 05:07:30:0 42.40 13.24 9.9 3.5 Italy
Stations used:
IV.CAMP IV.CESI IV.CESX IV.FAGN IV.FIAM IV.GUAR IV.GUMA
IV.INTR IV.LNSS IV.LPEL IV.MIDA IV.MTCE IV.OFFI IV.POFI
IV.RDP IV.RMP IV.RNI2 IV.SACS IV.TERO IV.TOLF MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 2.66e+21 dyne-cm
Mw = 3.55
Z = 2 km
Plane Strike Dip Rake
NP1 10 70 -60
NP2 131 36 -144
Principal Axes:
Axis Value Plunge Azimuth
T 2.66e+21 19 78
N 0.00e+00 28 179
P -2.66e+21 55 318
Moment Tensor: (dyne-cm)
Component Value
Mxx -3.83e+20
Mxy 9.21e+20
Mxz -7.55e+20
Myy 1.86e+21
Myz 1.66e+21
Mzz -1.48e+21
-----------###
----------------######
-------------------#########
--------------------##########
#----------------------###########
#-----------------------############
##---------- ----------#############
###---------- P ----------##############
###---------- ----------######### ##
####-----------------------######### T ###
#####---------------------########## ###
######--------------------################
######--------------------################
######------------------################
########----------------################
########--------------################
#########------------###############
###########--------###############
############----##############
##############---######-----
##########------------
####----------
Global CMT Convention Moment Tensor:
R T P
-1.48e+21 -7.55e+20 -1.66e+21
-7.55e+20 -3.83e+20 -9.21e+20
-1.66e+21 -9.21e+20 1.86e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20091020050730/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 1.0 10 70 -60 3.48 0.5024
WVFGRD96 2.0 10 70 -60 3.55 0.5417
WVFGRD96 3.0 10 65 -55 3.55 0.5327
WVFGRD96 4.0 15 65 -50 3.55 0.4978
WVFGRD96 5.0 10 65 -60 3.62 0.4822
WVFGRD96 6.0 20 75 -45 3.59 0.4485
WVFGRD96 7.0 25 65 -40 3.59 0.4306
WVFGRD96 8.0 215 75 30 3.58 0.4209
WVFGRD96 9.0 215 75 30 3.59 0.4096
WVFGRD96 10.0 215 75 30 3.60 0.3982
WVFGRD96 11.0 215 75 30 3.61 0.3866
WVFGRD96 12.0 215 75 30 3.62 0.3749
WVFGRD96 13.0 215 75 30 3.63 0.3620
WVFGRD96 14.0 220 70 35 3.64 0.3504
WVFGRD96 15.0 220 70 40 3.66 0.3358
WVFGRD96 16.0 220 70 40 3.67 0.3238
WVFGRD96 17.0 225 65 40 3.68 0.3138
WVFGRD96 18.0 225 65 40 3.68 0.3040
WVFGRD96 19.0 225 65 45 3.69 0.2956
WVFGRD96 20.0 225 65 45 3.70 0.2894
WVFGRD96 21.0 230 65 50 3.71 0.2835
WVFGRD96 22.0 230 65 50 3.72 0.2786
WVFGRD96 23.0 25 65 -30 3.70 0.2777
WVFGRD96 24.0 25 65 -30 3.71 0.2762
WVFGRD96 25.0 25 65 -30 3.72 0.2742
WVFGRD96 26.0 25 65 -30 3.73 0.2760
WVFGRD96 27.0 25 65 -30 3.74 0.2745
WVFGRD96 28.0 25 65 -35 3.75 0.2720
WVFGRD96 29.0 30 65 -30 3.76 0.2707
The best solution is
WVFGRD96 2.0 10 70 -60 3.55 0.5417
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 Oct 21 06:24:59 CDT 2009