2009/04/06 21:56:53 42.396 13.323 9.7 3.80 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/06 21:56:53:0 42.40 13.32 9.7 3.8 Italy
Stations used:
IV.CAMP IV.CERT IV.CING IV.FDMO IV.INTR IV.MNS IV.MTCE
IV.OFFI IV.RMP IV.TERO
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 6.10e+21 dyne-cm
Mw = 3.79
Z = 8 km
Plane Strike Dip Rake
NP1 10 75 -25
NP2 107 66 -164
Principal Axes:
Axis Value Plunge Azimuth
T 6.10e+21 6 60
N 0.00e+00 61 161
P -6.10e+21 28 327
Moment Tensor: (dyne-cm)
Component Value
Mxx -1.79e+21
Mxy 4.79e+21
Mxz -1.80e+21
Myy 3.07e+21
Myz 1.95e+21
Mzz -1.29e+21
-----------###
---------------#######
-------------------#########
----- ------------##########
------- P ------------##########
-------- ------------########## T
------------------------########## #
-------------------------###############
#------------------------###############
####---------------------#################
######-------------------#################
########-----------------#################
############------------##################
###############--------#################
####################---################-
#####################-----------------
###################-----------------
##################----------------
###############---------------
#############---------------
#########-------------
####----------
Global CMT Convention Moment Tensor:
R T P
-1.29e+21 -1.80e+21 -1.95e+21
-1.80e+21 -1.79e+21 -4.79e+21
-1.95e+21 -4.79e+21 3.07e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090406215653/index.html
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STK = 10
DIP = 75
RAKE = -25
MW = 3.79
HS = 8.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/06 21:56:53:0 42.40 13.32 9.7 3.8 Italy
Stations used:
IV.CAMP IV.CERT IV.CING IV.FDMO IV.INTR IV.MNS IV.MTCE
IV.OFFI IV.RMP IV.TERO
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 6.10e+21 dyne-cm
Mw = 3.79
Z = 8 km
Plane Strike Dip Rake
NP1 10 75 -25
NP2 107 66 -164
Principal Axes:
Axis Value Plunge Azimuth
T 6.10e+21 6 60
N 0.00e+00 61 161
P -6.10e+21 28 327
Moment Tensor: (dyne-cm)
Component Value
Mxx -1.79e+21
Mxy 4.79e+21
Mxz -1.80e+21
Myy 3.07e+21
Myz 1.95e+21
Mzz -1.29e+21
-----------###
---------------#######
-------------------#########
----- ------------##########
------- P ------------##########
-------- ------------########## T
------------------------########## #
-------------------------###############
#------------------------###############
####---------------------#################
######-------------------#################
########-----------------#################
############------------##################
###############--------#################
####################---################-
#####################-----------------
###################-----------------
##################----------------
###############---------------
#############---------------
#########-------------
####----------
Global CMT Convention Moment Tensor:
R T P
-1.29e+21 -1.80e+21 -1.95e+21
-1.80e+21 -1.79e+21 -4.79e+21
-1.95e+21 -4.79e+21 3.07e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090406215653/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 65 40 -85 3.49 0.2926
WVFGRD96 1.0 105 70 10 3.36 0.2870
WVFGRD96 2.0 110 65 20 3.50 0.3399
WVFGRD96 3.0 55 45 80 3.71 0.4018
WVFGRD96 4.0 0 60 -45 3.68 0.4622
WVFGRD96 5.0 5 65 -35 3.70 0.4943
WVFGRD96 6.0 190 70 -25 3.72 0.5068
WVFGRD96 7.0 190 70 -20 3.74 0.5101
WVFGRD96 8.0 10 75 -25 3.79 0.5144
WVFGRD96 9.0 195 75 -10 3.80 0.5050
WVFGRD96 10.0 195 75 -10 3.81 0.4932
WVFGRD96 11.0 195 75 -10 3.83 0.4776
WVFGRD96 12.0 195 80 0 3.84 0.4616
WVFGRD96 13.0 195 80 0 3.85 0.4467
WVFGRD96 14.0 195 80 0 3.86 0.4321
WVFGRD96 15.0 195 80 0 3.86 0.4182
WVFGRD96 16.0 195 80 0 3.87 0.4065
WVFGRD96 17.0 195 80 0 3.88 0.3952
WVFGRD96 18.0 15 90 -10 3.89 0.3844
WVFGRD96 19.0 15 90 -10 3.89 0.3766
WVFGRD96 20.0 15 90 -10 3.90 0.3710
WVFGRD96 21.0 20 65 0 3.90 0.3705
WVFGRD96 22.0 20 65 0 3.91 0.3710
WVFGRD96 23.0 20 65 0 3.92 0.3735
WVFGRD96 24.0 20 65 0 3.93 0.3769
WVFGRD96 25.0 20 65 0 3.93 0.3811
WVFGRD96 26.0 20 65 0 3.94 0.3858
WVFGRD96 27.0 20 65 0 3.95 0.3905
WVFGRD96 28.0 15 60 -10 3.97 0.3957
WVFGRD96 29.0 15 70 -10 3.97 0.4008
The best solution is
WVFGRD96 8.0 10 75 -25 3.79 0.5144
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 08:36:13 CDT 2009