2009/04/09 03:14:52 42.338 13.437 18.0 4.20 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/09 03:14:52:0 42.34 13.44 18.0 4.2 Italy
Stations used:
IV.ARVD IV.ASSB IV.CAFE IV.CAFR IV.CAMP IV.CASP IV.CERA
IV.CERT IV.CESX IV.CING IV.CSNT IV.FDMO IV.FRES IV.INTR
IV.LATE IV.LNSS IV.MAON IV.MGAB IV.MIDA IV.MSAG IV.MTCE
IV.MURB IV.NRCA IV.OFFI IV.PARC IV.PESA IV.POFI IV.PTRJ
IV.RDP IV.ROM9 IV.RSM IV.SACS IV.SGRT IV.TERO IV.TOLF
IV.TRTR IV.VAGA IV.VVLD
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 3.94e+22 dyne-cm
Mw = 4.33
Z = 16 km
Plane Strike Dip Rake
NP1 330 85 -55
NP2 67 35 -171
Principal Axes:
Axis Value Plunge Azimuth
T 3.94e+22 31 32
N 0.00e+00 35 146
P -3.94e+22 40 272
Moment Tensor: (dyne-cm)
Component Value
Mxx 2.09e+22
Mxy 1.37e+22
Mxz 1.42e+22
Myy -1.53e+22
Myz 2.85e+22
Mzz -5.60e+21
##############
-#####################
-----#######################
--------############# ######
-----------############ T ########
-------------########### #########
---------------#######################
------------------#####################-
-------------------####################-
------- -----------###################--
------- P ------------#################---
------- -------------###############----
------------------------#############-----
------------------------###########-----
-------------------------#########------
-------------------------######-------
#------------------------##---------
###--------------------##---------
######----------########------
#######################-----
#####################-
##############
Global CMT Convention Moment Tensor:
R T P
-5.60e+21 1.42e+22 -2.85e+22
1.42e+22 2.09e+22 -1.37e+22
-2.85e+22 -1.37e+22 -1.53e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090409031452/index.html
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STK = 330
DIP = 85
RAKE = -55
MW = 4.33
HS = 16.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/09 03:14:52:0 42.34 13.44 18.0 4.2 Italy
Stations used:
IV.ARVD IV.ASSB IV.CAFE IV.CAFR IV.CAMP IV.CASP IV.CERA
IV.CERT IV.CESX IV.CING IV.CSNT IV.FDMO IV.FRES IV.INTR
IV.LATE IV.LNSS IV.MAON IV.MGAB IV.MIDA IV.MSAG IV.MTCE
IV.MURB IV.NRCA IV.OFFI IV.PARC IV.PESA IV.POFI IV.PTRJ
IV.RDP IV.ROM9 IV.RSM IV.SACS IV.SGRT IV.TERO IV.TOLF
IV.TRTR IV.VAGA IV.VVLD
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 3.94e+22 dyne-cm
Mw = 4.33
Z = 16 km
Plane Strike Dip Rake
NP1 330 85 -55
NP2 67 35 -171
Principal Axes:
Axis Value Plunge Azimuth
T 3.94e+22 31 32
N 0.00e+00 35 146
P -3.94e+22 40 272
Moment Tensor: (dyne-cm)
Component Value
Mxx 2.09e+22
Mxy 1.37e+22
Mxz 1.42e+22
Myy -1.53e+22
Myz 2.85e+22
Mzz -5.60e+21
##############
-#####################
-----#######################
--------############# ######
-----------############ T ########
-------------########### #########
---------------#######################
------------------#####################-
-------------------####################-
------- -----------###################--
------- P ------------#################---
------- -------------###############----
------------------------#############-----
------------------------###########-----
-------------------------#########------
-------------------------######-------
#------------------------##---------
###--------------------##---------
######----------########------
#######################-----
#####################-
##############
Global CMT Convention Moment Tensor:
R T P
-5.60e+21 1.42e+22 -2.85e+22
1.42e+22 2.09e+22 -1.37e+22
-2.85e+22 -1.37e+22 -1.53e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090409031452/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 0.5 120 45 -95 3.82 0.2438
WVFGRD96 1.0 300 45 -90 3.81 0.1903
WVFGRD96 2.0 120 45 -90 3.99 0.2675
WVFGRD96 3.0 150 80 -60 3.99 0.2421
WVFGRD96 4.0 155 85 -60 4.03 0.2923
WVFGRD96 5.0 150 85 -65 4.05 0.3315
WVFGRD96 6.0 150 90 60 4.07 0.3651
WVFGRD96 7.0 150 90 55 4.09 0.3993
WVFGRD96 8.0 150 90 60 4.18 0.4252
WVFGRD96 9.0 150 90 60 4.20 0.4558
WVFGRD96 10.0 150 90 60 4.22 0.4793
WVFGRD96 11.0 150 90 55 4.24 0.4976
WVFGRD96 12.0 330 90 -55 4.26 0.5125
WVFGRD96 13.0 150 90 55 4.28 0.5229
WVFGRD96 14.0 330 85 -55 4.30 0.5316
WVFGRD96 15.0 150 90 55 4.31 0.5333
WVFGRD96 16.0 330 85 -55 4.33 0.5379
WVFGRD96 17.0 330 85 -55 4.34 0.5368
WVFGRD96 18.0 330 85 -55 4.35 0.5334
WVFGRD96 19.0 330 80 -55 4.37 0.5284
WVFGRD96 20.0 330 80 -55 4.38 0.5225
WVFGRD96 21.0 330 80 -55 4.39 0.5139
WVFGRD96 22.0 330 80 -55 4.40 0.5041
WVFGRD96 23.0 330 80 -55 4.41 0.4931
WVFGRD96 24.0 330 80 -60 4.41 0.4808
WVFGRD96 25.0 330 85 -60 4.42 0.4683
WVFGRD96 26.0 330 85 -60 4.42 0.4554
WVFGRD96 27.0 330 85 -60 4.43 0.4417
WVFGRD96 28.0 155 90 60 4.43 0.4249
WVFGRD96 29.0 150 90 60 4.43 0.4116
The best solution is
WVFGRD96 16.0 330 85 -55 4.33 0.5379
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=Wed Apr 15 20:01:12 CDT 2009