2009/04/20 11:43:06 42.278 13.503 9.9 3.0 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/20 11:43:06:0 42.28 13.50 9.9 3.0 Italy
Stations used:
IV.ASSB IV.CERA IV.CESX IV.FDMO IV.FIAM IV.LPEL IV.MNS
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 4.42e+20 dyne-cm
Mw = 3.03
Z = 7 km
Plane Strike Dip Rake
NP1 170 70 -35
NP2 273 57 -156
Principal Axes:
Axis Value Plunge Azimuth
T 4.42e+20 8 224
N 0.00e+00 50 324
P -4.42e+20 39 128
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.21e+20
Mxy 3.47e+20
Mxz 8.81e+19
Myy 4.16e+19
Myz -2.13e+20
Mzz -1.63e+20
---###########
------################
---------###################
----------####################
-----------#######################
------------########################
-------------#########################
-------#######----------------##########
---###########--------------------######
--#############-----------------------####
################------------------------##
################-------------------------#
################--------------------------
################------------------------
################------------- --------
################------------ P -------
###############------------ ------
## ##########-------------------
T ###########----------------
############--------------
############----------
##########----
Global CMT Convention Moment Tensor:
R T P
-1.63e+20 8.81e+19 2.13e+20
8.81e+19 1.21e+20 -3.47e+20
2.13e+20 -3.47e+20 4.16e+19
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090420114306/index.html
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STK = 170
DIP = 70
RAKE = -35
MW = 3.03
HS = 7.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/20 11:43:06:0 42.28 13.50 9.9 3.0 Italy
Stations used:
IV.ASSB IV.CERA IV.CESX IV.FDMO IV.FIAM IV.LPEL IV.MNS
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 4.42e+20 dyne-cm
Mw = 3.03
Z = 7 km
Plane Strike Dip Rake
NP1 170 70 -35
NP2 273 57 -156
Principal Axes:
Axis Value Plunge Azimuth
T 4.42e+20 8 224
N 0.00e+00 50 324
P -4.42e+20 39 128
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.21e+20
Mxy 3.47e+20
Mxz 8.81e+19
Myy 4.16e+19
Myz -2.13e+20
Mzz -1.63e+20
---###########
------################
---------###################
----------####################
-----------#######################
------------########################
-------------#########################
-------#######----------------##########
---###########--------------------######
--#############-----------------------####
################------------------------##
################-------------------------#
################--------------------------
################------------------------
################------------- --------
################------------ P -------
###############------------ ------
## ##########-------------------
T ###########----------------
############--------------
############----------
##########----
Global CMT Convention Moment Tensor:
R T P
-1.63e+20 8.81e+19 2.13e+20
8.81e+19 1.21e+20 -3.47e+20
2.13e+20 -3.47e+20 4.16e+19
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090420114306/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 0.5 180 60 35 2.76 0.5042
WVFGRD96 1.0 175 70 35 2.81 0.5041
WVFGRD96 2.0 -5 85 45 2.91 0.5282
WVFGRD96 3.0 165 75 -35 2.94 0.5671
WVFGRD96 4.0 170 75 -30 2.94 0.6031
WVFGRD96 5.0 170 75 -40 3.00 0.6154
WVFGRD96 6.0 170 75 -35 3.02 0.6275
WVFGRD96 7.0 170 70 -35 3.03 0.6304
WVFGRD96 8.0 175 75 -30 3.01 0.6205
WVFGRD96 9.0 175 75 -30 3.02 0.6116
WVFGRD96 10.0 175 75 -30 3.03 0.6039
WVFGRD96 11.0 175 75 -30 3.04 0.5948
WVFGRD96 12.0 175 75 -30 3.05 0.5851
WVFGRD96 13.0 175 75 -30 3.06 0.5732
WVFGRD96 14.0 175 75 -30 3.06 0.5603
WVFGRD96 15.0 175 65 -40 3.09 0.5524
WVFGRD96 16.0 175 65 -40 3.10 0.5405
WVFGRD96 17.0 175 60 -45 3.11 0.5281
WVFGRD96 18.0 175 60 -45 3.12 0.5175
WVFGRD96 19.0 170 50 -50 3.14 0.5115
WVFGRD96 20.0 175 55 -45 3.14 0.5032
WVFGRD96 21.0 170 50 -50 3.16 0.4938
WVFGRD96 22.0 170 50 -50 3.16 0.4840
WVFGRD96 23.0 350 75 10 3.20 0.4756
WVFGRD96 24.0 350 75 10 3.22 0.4753
WVFGRD96 25.0 335 85 0 3.28 0.4757
WVFGRD96 26.0 175 60 -40 3.17 0.4701
WVFGRD96 27.0 175 60 -40 3.18 0.4723
WVFGRD96 28.0 175 60 -40 3.19 0.4738
WVFGRD96 29.0 185 65 -35 3.19 0.4758
The best solution is
WVFGRD96 7.0 170 70 -35 3.03 0.6304
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 2 08:22:03 CDT 2009