2009/04/06 16:38:09 42.362 13.333 10.0 4.00 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/06 16:38:09:0 42.36 13.33 10.0 4.0 Italy
Stations used:
IV.ARVD IV.CAFR IV.CERT IV.CING IV.FAGN IV.FDMO IV.FIAM
IV.GUAR IV.INTR IV.MNS IV.MTCE IV.OFFI IV.RMP IV.TERO
IV.TRTR IV.VVLD
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 5.01e+22 dyne-cm
Mw = 4.40
Z = 11 km
Plane Strike Dip Rake
NP1 317 63 -121
NP2 190 40 -45
Principal Axes:
Axis Value Plunge Azimuth
T 5.01e+22 13 69
N 0.00e+00 27 333
P -5.01e+22 60 182
Moment Tensor: (dyne-cm)
Component Value
Mxx -6.74e+21
Mxy 1.54e+22
Mxz 2.57e+22
Myy 4.16e+22
Myz 1.08e+22
Mzz -3.49e+22
-------#######
--------##############
---------###################
#######-######################
#########----#####################
#########--------###################
#########-----------###############
#########--------------############# T #
########-----------------########### #
#########-------------------##############
#########--------------------#############
########----------------------############
########-----------------------###########
#######------------------------#########
########---------- -----------########
#######---------- P ------------######
#######--------- -------------####
######-------------------------###
#####------------------------#
#####-----------------------
####------------------
##------------
Global CMT Convention Moment Tensor:
R T P
-3.49e+22 2.57e+22 -1.08e+22
2.57e+22 -6.74e+21 -1.54e+22
-1.08e+22 -1.54e+22 4.16e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090406163809/index.html
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STK = 190
DIP = 40
RAKE = -45
MW = 4.40
HS = 11.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/06 16:38:09:0 42.36 13.33 10.0 4.0 Italy
Stations used:
IV.ARVD IV.CAFR IV.CERT IV.CING IV.FAGN IV.FDMO IV.FIAM
IV.GUAR IV.INTR IV.MNS IV.MTCE IV.OFFI IV.RMP IV.TERO
IV.TRTR IV.VVLD
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 5.01e+22 dyne-cm
Mw = 4.40
Z = 11 km
Plane Strike Dip Rake
NP1 317 63 -121
NP2 190 40 -45
Principal Axes:
Axis Value Plunge Azimuth
T 5.01e+22 13 69
N 0.00e+00 27 333
P -5.01e+22 60 182
Moment Tensor: (dyne-cm)
Component Value
Mxx -6.74e+21
Mxy 1.54e+22
Mxz 2.57e+22
Myy 4.16e+22
Myz 1.08e+22
Mzz -3.49e+22
-------#######
--------##############
---------###################
#######-######################
#########----#####################
#########--------###################
#########-----------###############
#########--------------############# T #
########-----------------########### #
#########-------------------##############
#########--------------------#############
########----------------------############
########-----------------------###########
#######------------------------#########
########---------- -----------########
#######---------- P ------------######
#######--------- -------------####
######-------------------------###
#####------------------------#
#####-----------------------
####------------------
##------------
Global CMT Convention Moment Tensor:
R T P
-3.49e+22 2.57e+22 -1.08e+22
2.57e+22 -6.74e+21 -1.54e+22
-1.08e+22 -1.54e+22 4.16e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090406163809/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 0.5 330 45 90 3.97 0.2855
WVFGRD96 1.0 135 45 70 3.96 0.2102
WVFGRD96 2.0 335 45 -90 4.13 0.2754
WVFGRD96 3.0 135 80 70 4.20 0.2985
WVFGRD96 4.0 135 80 70 4.22 0.3759
WVFGRD96 5.0 135 75 70 4.24 0.4208
WVFGRD96 6.0 220 30 -5 4.25 0.4499
WVFGRD96 7.0 215 35 -15 4.26 0.4728
WVFGRD96 8.0 210 30 -20 4.34 0.4849
WVFGRD96 9.0 200 35 -30 4.36 0.4979
WVFGRD96 10.0 195 35 -40 4.38 0.5044
WVFGRD96 11.0 190 40 -45 4.40 0.5073
WVFGRD96 12.0 180 45 -55 4.42 0.5068
WVFGRD96 13.0 175 45 -60 4.43 0.5019
WVFGRD96 14.0 175 45 -60 4.44 0.4925
WVFGRD96 15.0 180 50 -55 4.45 0.4808
WVFGRD96 16.0 180 50 -55 4.45 0.4677
WVFGRD96 17.0 175 50 -60 4.46 0.4540
WVFGRD96 18.0 175 50 -60 4.47 0.4432
WVFGRD96 19.0 175 50 -60 4.48 0.4324
WVFGRD96 20.0 175 55 -60 4.49 0.4217
WVFGRD96 21.0 175 55 -60 4.50 0.4148
WVFGRD96 22.0 175 55 -60 4.51 0.4057
WVFGRD96 23.0 175 55 -60 4.52 0.3946
WVFGRD96 24.0 175 55 -60 4.52 0.3816
WVFGRD96 25.0 180 55 -55 4.53 0.3685
WVFGRD96 26.0 180 55 -55 4.53 0.3550
WVFGRD96 27.0 5 50 -40 4.51 0.3476
WVFGRD96 28.0 5 45 -40 4.52 0.3411
WVFGRD96 29.0 5 45 -40 4.52 0.3346
The best solution is
WVFGRD96 11.0 190 40 -45 4.40 0.5073
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 WUS used for the waveform synthetic seismograms and for the surface wave eigenfunctions and dispersion is as follows:
MODEL.01
Model after 8 iterations
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
1.9000 3.4065 2.0089 2.2150 0.302E-02 0.679E-02 0.00 0.00 1.00 1.00
6.1000 5.5445 3.2953 2.6089 0.349E-02 0.784E-02 0.00 0.00 1.00 1.00
13.0000 6.2708 3.7396 2.7812 0.212E-02 0.476E-02 0.00 0.00 1.00 1.00
19.0000 6.4075 3.7680 2.8223 0.111E-02 0.249E-02 0.00 0.00 1.00 1.00
0.0000 7.9000 4.6200 3.2760 0.164E-10 0.370E-10 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=Thu Apr 16 08:50:02 CDT 2009