2009/09/11 06:34:37 46.545 9.692 7.2 3.2 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/09/11 06:34:37:0 46.54 9.69 7.2 3.2 Italy
Stations used:
CH.PLONS IV.BRMO MN.TUE SI.ABSI SI.BOSI SI.KOSI SI.MOSI
SI.ROSI
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 4.57e+20 dyne-cm
Mw = 3.04
Z = 11 km
Plane Strike Dip Rake
NP1 345 55 -45
NP2 105 55 -135
Principal Axes:
Axis Value Plunge Azimuth
T 4.57e+20 0 45
N 0.00e+00 35 135
P -4.57e+20 55 315
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.53e+20
Mxy 3.05e+20
Mxz -1.50e+20
Myy 1.51e+20
Myz 1.55e+20
Mzz -3.04e+20
---###########
----------############
---------------########### T
------------------#########
---------------------#############
-----------------------#############
----------- -----------#############
------------ P ------------#############
------------ -------------############
##---------------------------#############
###---------------------------############
#####-------------------------############
#######-----------------------############
#########---------------------##########
############------------------#########-
################-------------#####----
###########################---------
##########################--------
########################------
######################------
##################----
#############-
Global CMT Convention Moment Tensor:
R T P
-3.04e+20 -1.50e+20 -1.55e+20
-1.50e+20 1.53e+20 -3.05e+20
-1.55e+20 -3.05e+20 1.51e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090911063437/index.html
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STK = 345
DIP = 55
RAKE = -45
MW = 3.04
HS = 11.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/09/11 06:34:37:0 46.54 9.69 7.2 3.2 Italy
Stations used:
CH.PLONS IV.BRMO MN.TUE SI.ABSI SI.BOSI SI.KOSI SI.MOSI
SI.ROSI
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 4.57e+20 dyne-cm
Mw = 3.04
Z = 11 km
Plane Strike Dip Rake
NP1 345 55 -45
NP2 105 55 -135
Principal Axes:
Axis Value Plunge Azimuth
T 4.57e+20 0 45
N 0.00e+00 35 135
P -4.57e+20 55 315
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.53e+20
Mxy 3.05e+20
Mxz -1.50e+20
Myy 1.51e+20
Myz 1.55e+20
Mzz -3.04e+20
---###########
----------############
---------------########### T
------------------#########
---------------------#############
-----------------------#############
----------- -----------#############
------------ P ------------#############
------------ -------------############
##---------------------------#############
###---------------------------############
#####-------------------------############
#######-----------------------############
#########---------------------##########
############------------------#########-
################-------------#####----
###########################---------
##########################--------
########################------
######################------
##################----
#############-
Global CMT Convention Moment Tensor:
R T P
-3.04e+20 -1.50e+20 -1.55e+20
-1.50e+20 1.53e+20 -3.05e+20
-1.55e+20 -3.05e+20 1.51e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090911063437/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 1.0 115 70 30 2.79 0.3500
WVFGRD96 2.0 125 75 15 2.89 0.3696
WVFGRD96 3.0 110 55 5 2.87 0.3606
WVFGRD96 4.0 0 80 -40 2.84 0.3959
WVFGRD96 5.0 -5 75 -50 2.92 0.4313
WVFGRD96 6.0 350 70 -50 2.94 0.4712
WVFGRD96 7.0 340 55 -55 3.00 0.5123
WVFGRD96 8.0 340 55 -50 2.99 0.5501
WVFGRD96 9.0 345 55 -45 3.01 0.5673
WVFGRD96 10.0 345 55 -45 3.02 0.5757
WVFGRD96 11.0 345 55 -45 3.04 0.5770
WVFGRD96 12.0 350 55 -40 3.06 0.5712
WVFGRD96 13.0 350 55 -40 3.07 0.5635
WVFGRD96 14.0 350 55 -40 3.09 0.5519
WVFGRD96 15.0 350 55 -40 3.11 0.5363
WVFGRD96 16.0 165 40 -45 3.11 0.5229
WVFGRD96 17.0 170 40 -40 3.12 0.5065
WVFGRD96 18.0 350 75 -40 3.09 0.4957
WVFGRD96 19.0 355 85 -40 3.09 0.4891
WVFGRD96 20.0 185 80 35 3.11 0.4893
WVFGRD96 21.0 185 80 35 3.12 0.4865
WVFGRD96 22.0 185 80 35 3.13 0.4825
WVFGRD96 23.0 185 80 35 3.14 0.4790
WVFGRD96 24.0 185 80 35 3.15 0.4736
WVFGRD96 25.0 175 90 40 3.15 0.4707
WVFGRD96 26.0 175 90 40 3.17 0.4666
WVFGRD96 27.0 175 90 40 3.18 0.4621
WVFGRD96 28.0 -5 90 -35 3.19 0.4589
WVFGRD96 29.0 180 85 35 3.21 0.4584
The best solution is
WVFGRD96 11.0 345 55 -45 3.04 0.5770
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=Sat Sep 12 07:32:43 CDT 2009