2009/04/08 10:34:09 42.352 13.381 9.2 3.10 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/08 10:34:09:0 42.35 13.38 9.2 3.1 Italy
Stations used:
IV.ASSB IV.CERT IV.CESI IV.FDMO IV.GUAR IV.MNS IV.MTCE
IV.NRCA IV.OFFI IV.TERO
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 2.02e+21 dyne-cm
Mw = 3.47
Z = 5 km
Plane Strike Dip Rake
NP1 147 51 -98
NP2 340 40 -80
Principal Axes:
Axis Value Plunge Azimuth
T 2.02e+21 5 243
N 0.00e+00 6 152
P -2.02e+21 82 13
Moment Tensor: (dyne-cm)
Component Value
Mxx 3.74e+20
Mxy 8.02e+20
Mxz -3.70e+20
Myy 1.58e+21
Myz -2.33e+20
Mzz -1.96e+21
-#############
-----------###########
##---------------###########
##------------------##########
####--------------------##########
#####----------------------#########
######-----------------------#########
#######------------------------#########
########----------- ----------########
#########----------- P ----------#########
##########---------- -----------########
##########------------------------########
###########-----------------------########
###########----------------------#######
# ########---------------------#######
T ##########-------------------######
############-----------------#####
###############--------------#####
###############-----------####
#################-------####
####################--
##############
Global CMT Convention Moment Tensor:
R T P
-1.96e+21 -3.70e+20 2.33e+20
-3.70e+20 3.74e+20 -8.02e+20
2.33e+20 -8.02e+20 1.58e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090408103409/index.html
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STK = 340
DIP = 40
RAKE = -80
MW = 3.47
HS = 5.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/08 10:34:09:0 42.35 13.38 9.2 3.1 Italy
Stations used:
IV.ASSB IV.CERT IV.CESI IV.FDMO IV.GUAR IV.MNS IV.MTCE
IV.NRCA IV.OFFI IV.TERO
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 2.02e+21 dyne-cm
Mw = 3.47
Z = 5 km
Plane Strike Dip Rake
NP1 147 51 -98
NP2 340 40 -80
Principal Axes:
Axis Value Plunge Azimuth
T 2.02e+21 5 243
N 0.00e+00 6 152
P -2.02e+21 82 13
Moment Tensor: (dyne-cm)
Component Value
Mxx 3.74e+20
Mxy 8.02e+20
Mxz -3.70e+20
Myy 1.58e+21
Myz -2.33e+20
Mzz -1.96e+21
-#############
-----------###########
##---------------###########
##------------------##########
####--------------------##########
#####----------------------#########
######-----------------------#########
#######------------------------#########
########----------- ----------########
#########----------- P ----------#########
##########---------- -----------########
##########------------------------########
###########-----------------------########
###########----------------------#######
# ########---------------------#######
T ##########-------------------######
############-----------------#####
###############--------------#####
###############-----------####
#################-------####
####################--
##############
Global CMT Convention Moment Tensor:
R T P
-1.96e+21 -3.70e+20 2.33e+20
-3.70e+20 3.74e+20 -8.02e+20
2.33e+20 -8.02e+20 1.58e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090408103409/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 5 55 -40 3.15 0.2003
WVFGRD96 1.0 0 50 -50 3.19 0.2082
WVFGRD96 2.0 0 50 -50 3.27 0.2313
WVFGRD96 3.0 350 40 -70 3.34 0.2677
WVFGRD96 4.0 340 40 -85 3.38 0.2932
WVFGRD96 5.0 340 40 -80 3.47 0.3412
WVFGRD96 6.0 345 40 -80 3.46 0.3175
WVFGRD96 7.0 205 60 15 3.39 0.3036
WVFGRD96 8.0 195 80 5 3.41 0.3028
WVFGRD96 9.0 195 80 0 3.42 0.3010
WVFGRD96 10.0 15 80 0 3.43 0.3000
WVFGRD96 11.0 15 80 0 3.44 0.2979
WVFGRD96 12.0 15 75 -5 3.45 0.2973
WVFGRD96 13.0 15 75 -5 3.46 0.2971
WVFGRD96 14.0 15 75 -5 3.47 0.2977
WVFGRD96 15.0 15 75 -10 3.49 0.3006
WVFGRD96 16.0 130 75 35 3.49 0.3013
WVFGRD96 17.0 135 70 40 3.50 0.3055
WVFGRD96 18.0 135 70 40 3.52 0.3085
WVFGRD96 19.0 135 75 40 3.52 0.3101
WVFGRD96 20.0 135 75 40 3.54 0.3121
WVFGRD96 21.0 135 75 40 3.55 0.3130
WVFGRD96 22.0 130 75 40 3.55 0.3130
WVFGRD96 23.0 120 60 30 3.59 0.3162
WVFGRD96 24.0 120 60 30 3.60 0.3184
WVFGRD96 25.0 120 60 30 3.61 0.3180
WVFGRD96 26.0 120 60 30 3.62 0.3165
WVFGRD96 27.0 120 65 35 3.63 0.3141
WVFGRD96 28.0 200 65 15 3.63 0.3164
WVFGRD96 29.0 200 65 15 3.65 0.3223
The best solution is
WVFGRD96 5.0 340 40 -80 3.47 0.3412
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 May 1 07:57:50 CDT 2009