2009/04/09 04:32:44 42.445 13.420 8.1 4.00 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/09 04:32:44:0 42.44 13.42 8.1 4.0 Italy
Stations used:
IV.ASSB IV.BSSO IV.CAFI IV.CAFR IV.CAMP IV.CASP IV.CERT
IV.CESX IV.FDMO IV.FSSB IV.GIUL IV.GUAR IV.GUMA IV.INTR
IV.LATE IV.MAON IV.MIDA IV.MODR IV.MTCE IV.MTRZ IV.MURB
IV.NRCA IV.PESA IV.POFI IV.PTRJ IV.RDP IV.RNI2 IV.SACS
IV.SGG IV.TERO IV.TOLF IV.TRTR IV.VAGA
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 2.43e+22 dyne-cm
Mw = 4.19
Z = 11 km
Plane Strike Dip Rake
NP1 15 65 -30
NP2 119 63 -152
Principal Axes:
Axis Value Plunge Azimuth
T 2.43e+22 1 67
N 0.00e+00 52 159
P -2.43e+22 38 336
Moment Tensor: (dyne-cm)
Component Value
Mxx -8.90e+21
Mxy 1.42e+22
Mxz -1.06e+22
Myy 1.82e+22
Myz 5.23e+21
Mzz -9.29e+21
-------------#
-----------------#####
---------------------#######
-------- -----------########
---------- P ------------#########
----------- ------------#########
#--------------------------######### T
###-------------------------#########
####-----------------------#############
#######---------------------##############
########--------------------##############
##########-----------------###############
#############--------------###############
##############-----------###############
##################-------###############
#####################--###############
#####################-----#########-
###################---------------
################--------------
#############---------------
#########-------------
###-----------
Global CMT Convention Moment Tensor:
R T P
-9.29e+21 -1.06e+22 -5.23e+21
-1.06e+22 -8.90e+21 -1.42e+22
-5.23e+21 -1.42e+22 1.82e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090409043244/index.html
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STK = 15
DIP = 65
RAKE = -30
MW = 4.19
HS = 11.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/09 04:32:44:0 42.44 13.42 8.1 4.0 Italy
Stations used:
IV.ASSB IV.BSSO IV.CAFI IV.CAFR IV.CAMP IV.CASP IV.CERT
IV.CESX IV.FDMO IV.FSSB IV.GIUL IV.GUAR IV.GUMA IV.INTR
IV.LATE IV.MAON IV.MIDA IV.MODR IV.MTCE IV.MTRZ IV.MURB
IV.NRCA IV.PESA IV.POFI IV.PTRJ IV.RDP IV.RNI2 IV.SACS
IV.SGG IV.TERO IV.TOLF IV.TRTR IV.VAGA
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 2.43e+22 dyne-cm
Mw = 4.19
Z = 11 km
Plane Strike Dip Rake
NP1 15 65 -30
NP2 119 63 -152
Principal Axes:
Axis Value Plunge Azimuth
T 2.43e+22 1 67
N 0.00e+00 52 159
P -2.43e+22 38 336
Moment Tensor: (dyne-cm)
Component Value
Mxx -8.90e+21
Mxy 1.42e+22
Mxz -1.06e+22
Myy 1.82e+22
Myz 5.23e+21
Mzz -9.29e+21
-------------#
-----------------#####
---------------------#######
-------- -----------########
---------- P ------------#########
----------- ------------#########
#--------------------------######### T
###-------------------------#########
####-----------------------#############
#######---------------------##############
########--------------------##############
##########-----------------###############
#############--------------###############
##############-----------###############
##################-------###############
#####################--###############
#####################-----#########-
###################---------------
################--------------
#############---------------
#########-------------
###-----------
Global CMT Convention Moment Tensor:
R T P
-9.29e+21 -1.06e+22 -5.23e+21
-1.06e+22 -8.90e+21 -1.42e+22
-5.23e+21 -1.42e+22 1.82e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090409043244/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 0.5 345 45 85 3.79 0.2120
WVFGRD96 1.0 20 70 -25 3.71 0.1941
WVFGRD96 2.0 15 60 -30 3.88 0.2398
WVFGRD96 3.0 15 70 -40 3.95 0.2697
WVFGRD96 4.0 10 65 -45 4.00 0.2990
WVFGRD96 5.0 10 65 -45 4.03 0.3275
WVFGRD96 6.0 10 65 -40 4.05 0.3476
WVFGRD96 7.0 15 65 -35 4.07 0.3599
WVFGRD96 8.0 10 60 -40 4.14 0.3751
WVFGRD96 9.0 10 60 -40 4.16 0.3832
WVFGRD96 10.0 10 60 -35 4.17 0.3869
WVFGRD96 11.0 15 65 -30 4.19 0.3879
WVFGRD96 12.0 15 65 -30 4.20 0.3865
WVFGRD96 13.0 15 65 -30 4.22 0.3825
WVFGRD96 14.0 15 65 -25 4.23 0.3774
WVFGRD96 15.0 15 65 -25 4.24 0.3705
WVFGRD96 16.0 15 65 -25 4.25 0.3625
WVFGRD96 17.0 15 65 -25 4.26 0.3543
WVFGRD96 18.0 15 65 -25 4.27 0.3447
WVFGRD96 19.0 15 60 -25 4.28 0.3354
WVFGRD96 20.0 15 60 -25 4.28 0.3262
WVFGRD96 21.0 15 60 -20 4.29 0.3183
WVFGRD96 22.0 15 60 -20 4.30 0.3104
WVFGRD96 23.0 15 60 -20 4.30 0.3025
WVFGRD96 24.0 20 60 -15 4.31 0.2959
WVFGRD96 25.0 20 60 -15 4.31 0.2894
WVFGRD96 26.0 20 60 -15 4.32 0.2841
WVFGRD96 27.0 20 60 -15 4.32 0.2791
WVFGRD96 28.0 20 60 -15 4.33 0.2748
WVFGRD96 29.0 20 60 -15 4.33 0.2704
The best solution is
WVFGRD96 11.0 15 65 -30 4.19 0.3879
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 9 08:35:41 CDT 2009