2008/10/01 22:47:37 42.590 13.287 15.4 3.1 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2008/10/01 22:47:37:2 42.59 13.29 15.4 3.1 Italy
Stations used:
IV.CERT IV.CESX IV.GUAR IV.MNS IV.MTCE 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 = 7.94e+20 dyne-cm
Mw = 3.20
Z = 15 km
Plane Strike Dip Rake
NP1 320 75 -90
NP2 140 15 -90
Principal Axes:
Axis Value Plunge Azimuth
T 7.94e+20 30 50
N 0.00e+00 -0 140
P -7.94e+20 60 230
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.64e+20
Mxy 1.96e+20
Mxz 4.42e+20
Myy 2.33e+20
Myz 5.27e+20
Mzz -3.97e+20
##############
######################
-###########################
------########################
#---------################ #####
#------------############## T ######
#---------------############ #######
##-----------------#####################
#--------------------###################
##----------------------##################
##-----------------------#################
###------------------------###############
###----------- -----------##############
##----------- P ------------############
###---------- -------------###########
###--------------------------#########
###--------------------------#######
####-------------------------#####
####------------------------##
#####----------------------#
######---------------#
##############
Global CMT Convention Moment Tensor:
R T P
-3.97e+20 4.42e+20 -5.27e+20
4.42e+20 1.64e+20 -1.96e+20
-5.27e+20 -1.96e+20 2.33e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20081001224737/index.html
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STK = 320
DIP = 75
RAKE = -90
MW = 3.20
HS = 15.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2008/10/01 22:47:37:2 42.59 13.29 15.4 3.1 Italy
Stations used:
IV.CERT IV.CESX IV.GUAR IV.MNS IV.MTCE 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 = 7.94e+20 dyne-cm
Mw = 3.20
Z = 15 km
Plane Strike Dip Rake
NP1 320 75 -90
NP2 140 15 -90
Principal Axes:
Axis Value Plunge Azimuth
T 7.94e+20 30 50
N 0.00e+00 -0 140
P -7.94e+20 60 230
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.64e+20
Mxy 1.96e+20
Mxz 4.42e+20
Myy 2.33e+20
Myz 5.27e+20
Mzz -3.97e+20
##############
######################
-###########################
------########################
#---------################ #####
#------------############## T ######
#---------------############ #######
##-----------------#####################
#--------------------###################
##----------------------##################
##-----------------------#################
###------------------------###############
###----------- -----------##############
##----------- P ------------############
###---------- -------------###########
###--------------------------#########
###--------------------------#######
####-------------------------#####
####------------------------##
#####----------------------#
######---------------#
##############
Global CMT Convention Moment Tensor:
R T P
-3.97e+20 4.42e+20 -5.27e+20
4.42e+20 1.64e+20 -1.96e+20
-5.27e+20 -1.96e+20 2.33e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20081001224737/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 45 -90 2.93 0.3071
WVFGRD96 2.0 335 40 -85 3.01 0.2911
WVFGRD96 3.0 320 85 -80 2.98 0.2760
WVFGRD96 4.0 320 85 -80 2.96 0.3264
WVFGRD96 5.0 320 85 -80 3.08 0.3682
WVFGRD96 6.0 325 85 -80 3.08 0.4087
WVFGRD96 7.0 325 85 -80 3.09 0.4417
WVFGRD96 8.0 320 80 -80 3.06 0.4668
WVFGRD96 9.0 325 80 -80 3.07 0.4861
WVFGRD96 10.0 325 75 -80 3.09 0.4998
WVFGRD96 11.0 320 75 -85 3.11 0.5126
WVFGRD96 12.0 120 15 -110 3.12 0.5214
WVFGRD96 13.0 325 75 -85 3.13 0.5278
WVFGRD96 14.0 130 20 -100 3.15 0.5299
WVFGRD96 15.0 320 75 -90 3.20 0.5305
WVFGRD96 16.0 320 75 -90 3.21 0.5267
WVFGRD96 17.0 320 75 -90 3.22 0.5213
WVFGRD96 18.0 170 15 -60 3.23 0.5119
WVFGRD96 19.0 170 15 -60 3.24 0.5036
WVFGRD96 20.0 190 20 -40 3.26 0.4945
WVFGRD96 21.0 190 20 -40 3.27 0.4842
WVFGRD96 22.0 185 20 -45 3.27 0.4748
WVFGRD96 23.0 175 20 -55 3.28 0.4664
WVFGRD96 24.0 330 65 -85 3.27 0.4653
WVFGRD96 25.0 330 65 -85 3.28 0.4624
WVFGRD96 26.0 330 65 -85 3.28 0.4574
WVFGRD96 27.0 140 25 -100 3.29 0.4487
WVFGRD96 28.0 155 20 -85 3.29 0.4400
WVFGRD96 29.0 160 20 -80 3.30 0.4309
The best solution is
WVFGRD96 15.0 320 75 -90 3.20 0.5305
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 Nov 6 08:21:16 CST 2009