2010/09/01 13:11:32 42.840 12.671 2.4 2.9 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2010/09/01 13:11:32:0 42.84 12.67 2.4 2.9 Italy
Stations used:
IV.AOI IV.ARVD IV.ASQU IV.ATPC IV.ATVO IV.CASP IV.CESI
IV.CING IV.CRE IV.CSNT IV.FAGN IV.GUMA IV.LATE IV.MAON
IV.MCIV IV.OFFI IV.PARC IV.POFI IV.SACS IV.SASS IV.SNTG
IV.TERO MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 9.44e+20 dyne-cm
Mw = 3.25
Z = 6 km
Plane Strike Dip Rake
NP1 5 80 -95
NP2 212 11 -64
Principal Axes:
Axis Value Plunge Azimuth
T 9.44e+20 35 99
N 0.00e+00 5 6
P -9.44e+20 55 269
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.65e+19
Mxy -1.08e+20
Mxz -6.28e+19
Myy 3.05e+20
Myz 8.82e+20
Mzz -3.22e+20
#####----####-
####---------#########
####-------------###########
##----------------############
###-----------------##############
##-------------------###############
##--------------------################
##---------------------#################
##---------------------#################
##----------------------##################
##--------- ----------##################
##--------- P ---------########## ######
##--------- ---------########## T ######
#---------------------########## #####
##--------------------##################
#--------------------#################
#------------------#################
#-----------------################
---------------###############
#-------------##############
----------############
------########
Global CMT Convention Moment Tensor:
R T P
-3.22e+20 -6.28e+19 -8.82e+20
-6.28e+19 1.65e+19 1.08e+20
-8.82e+20 1.08e+20 3.05e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20100901131132/index.html
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STK = 5
DIP = 80
RAKE = -95
MW = 3.25
HS = 6.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2010/09/01 13:11:32:0 42.84 12.67 2.4 2.9 Italy
Stations used:
IV.AOI IV.ARVD IV.ASQU IV.ATPC IV.ATVO IV.CASP IV.CESI
IV.CING IV.CRE IV.CSNT IV.FAGN IV.GUMA IV.LATE IV.MAON
IV.MCIV IV.OFFI IV.PARC IV.POFI IV.SACS IV.SASS IV.SNTG
IV.TERO MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 9.44e+20 dyne-cm
Mw = 3.25
Z = 6 km
Plane Strike Dip Rake
NP1 5 80 -95
NP2 212 11 -64
Principal Axes:
Axis Value Plunge Azimuth
T 9.44e+20 35 99
N 0.00e+00 5 6
P -9.44e+20 55 269
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.65e+19
Mxy -1.08e+20
Mxz -6.28e+19
Myy 3.05e+20
Myz 8.82e+20
Mzz -3.22e+20
#####----####-
####---------#########
####-------------###########
##----------------############
###-----------------##############
##-------------------###############
##--------------------################
##---------------------#################
##---------------------#################
##----------------------##################
##--------- ----------##################
##--------- P ---------########## ######
##--------- ---------########## T ######
#---------------------########## #####
##--------------------##################
#--------------------#################
#------------------#################
#-----------------################
---------------###############
#-------------##############
----------############
------########
Global CMT Convention Moment Tensor:
R T P
-3.22e+20 -6.28e+19 -8.82e+20
-6.28e+19 1.65e+19 1.08e+20
-8.82e+20 1.08e+20 3.05e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20100901131132/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 35 -85 3.08 0.3493
WVFGRD96 2.0 5 85 -80 3.24 0.4067
WVFGRD96 3.0 185 90 80 3.19 0.5102
WVFGRD96 4.0 185 90 75 3.16 0.5536
WVFGRD96 5.0 185 90 80 3.26 0.5709
WVFGRD96 6.0 5 80 -95 3.25 0.5752
WVFGRD96 7.0 210 10 -65 3.24 0.5639
WVFGRD96 8.0 185 90 75 3.19 0.5427
WVFGRD96 9.0 180 90 70 3.20 0.5232
WVFGRD96 10.0 0 90 -70 3.21 0.5010
WVFGRD96 11.0 180 90 70 3.21 0.4768
WVFGRD96 12.0 185 85 70 3.22 0.4517
WVFGRD96 13.0 185 85 70 3.22 0.4275
WVFGRD96 14.0 5 90 -70 3.23 0.4040
WVFGRD96 15.0 0 90 -70 3.27 0.3808
WVFGRD96 16.0 185 85 75 3.27 0.3557
WVFGRD96 17.0 185 80 75 3.28 0.3311
WVFGRD96 18.0 175 65 70 3.29 0.3095
WVFGRD96 19.0 175 65 70 3.30 0.2927
WVFGRD96 20.0 175 60 70 3.30 0.2763
WVFGRD96 21.0 175 60 70 3.31 0.2610
WVFGRD96 22.0 175 60 70 3.31 0.2461
WVFGRD96 23.0 170 60 60 3.32 0.2330
WVFGRD96 24.0 170 60 60 3.33 0.2237
WVFGRD96 25.0 170 60 60 3.33 0.2165
WVFGRD96 26.0 175 55 65 3.33 0.2089
WVFGRD96 27.0 40 25 -55 3.34 0.2077
WVFGRD96 28.0 45 25 -50 3.35 0.2108
WVFGRD96 29.0 45 25 -50 3.36 0.2129
The best solution is
WVFGRD96 6.0 5 80 -95 3.25 0.5752
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 1 10:46:56 CDT 2010