2010/08/31 12:06:25 42.543 13.201 2.3 3.3 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2010/08/31 12:06:25:0 42.54 13.20 2.3 3.3 Italy
Stations used:
IV.ARVD IV.CERT IV.CESI IV.CING IV.FAGN IV.FIAM IV.FSSB
IV.GIUL IV.GUAR IV.GUMA IV.LATE IV.MGAB IV.MNS IV.MTCE
IV.OFFI IV.PIEI IV.SACS IV.TOLF MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 1.16e+21 dyne-cm
Mw = 3.31
Z = 5 km
Plane Strike Dip Rake
NP1 114 60 -93
NP2 300 30 -85
Principal Axes:
Axis Value Plunge Azimuth
T 1.16e+21 15 206
N 0.00e+00 2 116
P -1.16e+21 75 16
Moment Tensor: (dyne-cm)
Component Value
Mxx 7.95e+20
Mxy 4.09e+20
Mxz -5.45e+20
Myy 2.07e+20
Myz -2.13e+20
Mzz -1.00e+21
##############
######################
########----################
##------------------##########
#------------------------#########
-----------------------------#######
--------------------------------######
##------------------ -----------######
###----------------- P -------------####
#####---------------- --------------####
#######-------------------------------####
#########------------------------------###
###########----------------------------###
#############-------------------------##
################-----------------------#
####################-----------------#
####################################
##################################
##### ######################
#### T #####################
# ##################
##############
Global CMT Convention Moment Tensor:
R T P
-1.00e+21 -5.45e+20 2.13e+20
-5.45e+20 7.95e+20 -4.09e+20
2.13e+20 -4.09e+20 2.07e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20100831120625/index.html
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STK = 300
DIP = 30
RAKE = -85
MW = 3.31
HS = 5.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2010/08/31 12:06:25:0 42.54 13.20 2.3 3.3 Italy
Stations used:
IV.ARVD IV.CERT IV.CESI IV.CING IV.FAGN IV.FIAM IV.FSSB
IV.GIUL IV.GUAR IV.GUMA IV.LATE IV.MGAB IV.MNS IV.MTCE
IV.OFFI IV.PIEI IV.SACS IV.TOLF MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 1.16e+21 dyne-cm
Mw = 3.31
Z = 5 km
Plane Strike Dip Rake
NP1 114 60 -93
NP2 300 30 -85
Principal Axes:
Axis Value Plunge Azimuth
T 1.16e+21 15 206
N 0.00e+00 2 116
P -1.16e+21 75 16
Moment Tensor: (dyne-cm)
Component Value
Mxx 7.95e+20
Mxy 4.09e+20
Mxz -5.45e+20
Myy 2.07e+20
Myz -2.13e+20
Mzz -1.00e+21
##############
######################
########----################
##------------------##########
#------------------------#########
-----------------------------#######
--------------------------------######
##------------------ -----------######
###----------------- P -------------####
#####---------------- --------------####
#######-------------------------------####
#########------------------------------###
###########----------------------------###
#############-------------------------##
################-----------------------#
####################-----------------#
####################################
##################################
##### ######################
#### T #####################
# ##################
##############
Global CMT Convention Moment Tensor:
R T P
-1.00e+21 -5.45e+20 2.13e+20
-5.45e+20 7.95e+20 -4.09e+20
2.13e+20 -4.09e+20 2.07e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20100831120625/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 1.0 330 25 -30 3.12 0.3245
WVFGRD96 2.0 325 20 -40 3.20 0.3910
WVFGRD96 3.0 310 25 -70 3.20 0.4511
WVFGRD96 4.0 300 30 -85 3.22 0.4867
WVFGRD96 5.0 300 30 -85 3.31 0.5057
WVFGRD96 6.0 305 35 -80 3.30 0.4811
WVFGRD96 7.0 105 60 -105 3.26 0.4297
WVFGRD96 8.0 315 35 -65 3.21 0.3686
WVFGRD96 9.0 340 70 20 3.23 0.3317
WVFGRD96 10.0 340 70 20 3.24 0.3160
WVFGRD96 11.0 340 70 20 3.25 0.2996
WVFGRD96 12.0 340 70 20 3.25 0.2831
WVFGRD96 13.0 345 70 25 3.26 0.2683
WVFGRD96 14.0 345 70 25 3.26 0.2545
WVFGRD96 15.0 345 65 25 3.28 0.2405
WVFGRD96 16.0 350 60 35 3.29 0.2313
WVFGRD96 17.0 350 60 35 3.30 0.2234
WVFGRD96 18.0 340 70 15 3.30 0.2175
WVFGRD96 19.0 345 60 25 3.31 0.2129
WVFGRD96 20.0 335 65 -25 3.28 0.2095
WVFGRD96 21.0 335 65 -25 3.29 0.2075
WVFGRD96 22.0 335 70 -20 3.31 0.2067
WVFGRD96 23.0 335 70 -20 3.32 0.2078
WVFGRD96 24.0 335 65 -25 3.32 0.2093
WVFGRD96 25.0 335 60 -25 3.33 0.2125
WVFGRD96 26.0 335 60 -25 3.35 0.2154
WVFGRD96 27.0 335 60 -25 3.36 0.2175
WVFGRD96 28.0 325 65 -40 3.37 0.2196
WVFGRD96 29.0 320 65 -40 3.39 0.2233
The best solution is
WVFGRD96 5.0 300 30 -85 3.31 0.5057
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=Tue Aug 31 08:26:15 CDT 2010