2009/06/08 12:49:47 42.351 13.462 7.3 3.00 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/06/08 12:49:47:0 42.35 13.46 7.3 3.0 Italy
Stations used:
IV.CAMP IV.FAGN IV.FIAM IV.TERO
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 2.21e+20 dyne-cm
Mw = 2.83
Z = 1 km
Plane Strike Dip Rake
NP1 300 50 -85
NP2 112 40 -96
Principal Axes:
Axis Value Plunge Azimuth
T 2.21e+20 5 26
N 0.00e+00 4 117
P -2.21e+20 84 245
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.76e+20
Mxy 8.66e+19
Mxz 2.70e+19
Myy 4.15e+19
Myz 2.99e+19
Mzz -2.17e+20
##############
################## T #
##################### ####
##############################
###-----------####################
--------------------################
-------------------------#############
#---------------------------############
#------------------------------#########
###------------------------------#########
###--------------- --------------#######
####-------------- P ---------------######
#####------------- ----------------#####
######-------------------------------###
########-----------------------------###
#########----------------------------#
###########-----------------------##
##############----------------####
##############################
############################
######################
##############
Global CMT Convention Moment Tensor:
R T P
-2.17e+20 2.70e+19 -2.99e+19
2.70e+19 1.76e+20 -8.66e+19
-2.99e+19 -8.66e+19 4.15e+19
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090608124947/index.html
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STK = 300
DIP = 50
RAKE = -85
MW = 2.83
HS = 1.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/06/08 12:49:47:0 42.35 13.46 7.3 3.0 Italy
Stations used:
IV.CAMP IV.FAGN IV.FIAM IV.TERO
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 2.21e+20 dyne-cm
Mw = 2.83
Z = 1 km
Plane Strike Dip Rake
NP1 300 50 -85
NP2 112 40 -96
Principal Axes:
Axis Value Plunge Azimuth
T 2.21e+20 5 26
N 0.00e+00 4 117
P -2.21e+20 84 245
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.76e+20
Mxy 8.66e+19
Mxz 2.70e+19
Myy 4.15e+19
Myz 2.99e+19
Mzz -2.17e+20
##############
################## T #
##################### ####
##############################
###-----------####################
--------------------################
-------------------------#############
#---------------------------############
#------------------------------#########
###------------------------------#########
###--------------- --------------#######
####-------------- P ---------------######
#####------------- ----------------#####
######-------------------------------###
########-----------------------------###
#########----------------------------#
###########-----------------------##
##############----------------####
##############################
############################
######################
##############
Global CMT Convention Moment Tensor:
R T P
-2.17e+20 2.70e+19 -2.99e+19
2.70e+19 1.76e+20 -8.66e+19
-2.99e+19 -8.66e+19 4.15e+19
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090608124947/index.html
|
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 0.5 305 55 -80 2.80 0.2514
WVFGRD96 1.0 300 50 -85 2.83 0.2650
WVFGRD96 2.0 300 50 -80 2.88 0.2510
WVFGRD96 3.0 320 60 -60 2.89 0.2100
WVFGRD96 4.0 320 60 -60 2.91 0.1903
WVFGRD96 5.0 150 35 -35 2.92 0.1808
WVFGRD96 6.0 320 70 -70 3.02 0.1794
WVFGRD96 7.0 320 70 -80 3.05 0.1826
WVFGRD96 8.0 150 40 -25 2.91 0.1807
WVFGRD96 9.0 150 45 -20 2.92 0.1813
WVFGRD96 10.0 115 30 -100 3.00 0.1812
WVFGRD96 11.0 135 40 -45 2.97 0.1810
WVFGRD96 12.0 135 40 -40 2.97 0.1811
WVFGRD96 13.0 135 40 -35 2.97 0.1790
WVFGRD96 14.0 140 45 -25 2.98 0.1774
WVFGRD96 15.0 135 40 -25 3.01 0.1771
WVFGRD96 16.0 135 45 -20 3.03 0.1770
WVFGRD96 17.0 135 45 -20 3.04 0.1766
WVFGRD96 18.0 135 45 -20 3.05 0.1758
WVFGRD96 19.0 130 45 -20 3.07 0.1754
WVFGRD96 20.0 130 45 -20 3.08 0.1752
WVFGRD96 21.0 130 45 -20 3.09 0.1752
WVFGRD96 22.0 130 50 -20 3.11 0.1739
WVFGRD96 23.0 130 50 -20 3.11 0.1730
WVFGRD96 24.0 130 50 -20 3.12 0.1723
WVFGRD96 25.0 130 50 -20 3.12 0.1732
WVFGRD96 26.0 130 55 -20 3.14 0.1735
WVFGRD96 27.0 125 55 -20 3.18 0.1738
WVFGRD96 28.0 125 55 -15 3.20 0.1726
WVFGRD96 29.0 125 60 -15 3.23 0.1683
The best solution is
WVFGRD96 1.0 300 50 -85 2.83 0.2650
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=Mon Jun 8 17:52:07 CDT 2009