2009/04/18 09:05:56 42.441 13.361 14.6 3.80 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/18 09:05:56:0 42.44 13.36 14.6 3.8 Italy
Stations used:
IV.AOI IV.ARVD IV.ASSB IV.BSSO IV.CAFI IV.CAFR IV.CERA
IV.CERT IV.CESI IV.CESX IV.CIGN IV.CING IV.FAGN IV.FDMO
IV.FIAM IV.FRES IV.FSSB IV.GIUL IV.GUAR IV.GUMA IV.INTR
IV.LATE IV.LPEL IV.MAON IV.MGAB IV.MIDA IV.MNS IV.MODR
IV.MTCE IV.MURB IV.NRCA IV.OFFI IV.PARC IV.PIEI IV.POFI
IV.RMP IV.RNI2 IV.SACS IV.SGG IV.TERO IV.TOLF IV.TRIV
IV.VAGA IV.VVLD MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 4.62e+21 dyne-cm
Mw = 3.71
Z = 10 km
Plane Strike Dip Rake
NP1 306 69 -112
NP2 175 30 -45
Principal Axes:
Axis Value Plunge Azimuth
T 4.62e+21 21 53
N 0.00e+00 21 314
P -4.62e+21 60 184
Moment Tensor: (dyne-cm)
Component Value
Mxx 3.05e+20
Mxy 1.86e+21
Mxz 2.96e+21
Myy 2.53e+21
Myz 1.38e+21
Mzz -2.83e+21
---###########
----##################
-----#######################
----##########################
###--######################## ##
#####------################### T ###
######----------############### ####
######--------------####################
######-----------------#################
######--------------------################
######----------------------##############
######------------------------############
#######-------------------------##########
######---------------------------#######
######------------ -------------######
######----------- P --------------####
######---------- ---------------##
######----------------------------
#####-------------------------
######----------------------
######----------------
#####---------
Global CMT Convention Moment Tensor:
R T P
-2.83e+21 2.96e+21 -1.38e+21
2.96e+21 3.05e+20 -1.86e+21
-1.38e+21 -1.86e+21 2.53e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090418090556/index.html
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STK = 175
DIP = 30
RAKE = -45
MW = 3.71
HS = 10.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/18 09:05:56:0 42.44 13.36 14.6 3.8 Italy
Stations used:
IV.AOI IV.ARVD IV.ASSB IV.BSSO IV.CAFI IV.CAFR IV.CERA
IV.CERT IV.CESI IV.CESX IV.CIGN IV.CING IV.FAGN IV.FDMO
IV.FIAM IV.FRES IV.FSSB IV.GIUL IV.GUAR IV.GUMA IV.INTR
IV.LATE IV.LPEL IV.MAON IV.MGAB IV.MIDA IV.MNS IV.MODR
IV.MTCE IV.MURB IV.NRCA IV.OFFI IV.PARC IV.PIEI IV.POFI
IV.RMP IV.RNI2 IV.SACS IV.SGG IV.TERO IV.TOLF IV.TRIV
IV.VAGA IV.VVLD MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 4.62e+21 dyne-cm
Mw = 3.71
Z = 10 km
Plane Strike Dip Rake
NP1 306 69 -112
NP2 175 30 -45
Principal Axes:
Axis Value Plunge Azimuth
T 4.62e+21 21 53
N 0.00e+00 21 314
P -4.62e+21 60 184
Moment Tensor: (dyne-cm)
Component Value
Mxx 3.05e+20
Mxy 1.86e+21
Mxz 2.96e+21
Myy 2.53e+21
Myz 1.38e+21
Mzz -2.83e+21
---###########
----##################
-----#######################
----##########################
###--######################## ##
#####------################### T ###
######----------############### ####
######--------------####################
######-----------------#################
######--------------------################
######----------------------##############
######------------------------############
#######-------------------------##########
######---------------------------#######
######------------ -------------######
######----------- P --------------####
######---------- ---------------##
######----------------------------
#####-------------------------
######----------------------
######----------------
#####---------
Global CMT Convention Moment Tensor:
R T P
-2.83e+21 2.96e+21 -1.38e+21
2.96e+21 3.05e+20 -1.86e+21
-1.38e+21 -1.86e+21 2.53e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090418090556/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 0.5 145 45 -85 3.47 0.3466
WVFGRD96 1.0 320 40 -90 3.51 0.3089
WVFGRD96 2.0 185 30 -20 3.55 0.2998
WVFGRD96 3.0 190 25 -20 3.56 0.3668
WVFGRD96 4.0 185 25 -35 3.57 0.4236
WVFGRD96 5.0 175 20 -45 3.69 0.4820
WVFGRD96 6.0 170 25 -55 3.71 0.5352
WVFGRD96 7.0 170 25 -55 3.72 0.5716
WVFGRD96 8.0 175 30 -50 3.69 0.5884
WVFGRD96 9.0 175 30 -45 3.70 0.6010
WVFGRD96 10.0 175 30 -45 3.71 0.6071
WVFGRD96 11.0 175 30 -45 3.72 0.6069
WVFGRD96 12.0 175 30 -45 3.73 0.6009
WVFGRD96 13.0 180 30 -40 3.73 0.5915
WVFGRD96 14.0 180 30 -40 3.74 0.5799
WVFGRD96 15.0 180 30 -40 3.79 0.5724
WVFGRD96 16.0 180 30 -40 3.79 0.5571
WVFGRD96 17.0 185 30 -30 3.80 0.5410
WVFGRD96 18.0 185 30 -30 3.81 0.5254
WVFGRD96 19.0 185 30 -30 3.82 0.5083
WVFGRD96 20.0 185 30 -30 3.83 0.4922
WVFGRD96 21.0 180 30 -35 3.83 0.4762
WVFGRD96 22.0 180 30 -35 3.84 0.4616
WVFGRD96 23.0 180 30 -35 3.85 0.4481
WVFGRD96 24.0 180 35 -30 3.85 0.4347
WVFGRD96 25.0 180 35 -30 3.86 0.4210
WVFGRD96 26.0 180 35 -30 3.86 0.4066
WVFGRD96 27.0 180 35 -30 3.86 0.3921
WVFGRD96 28.0 180 35 -30 3.86 0.3782
WVFGRD96 29.0 180 35 -30 3.87 0.3649
The best solution is
WVFGRD96 10.0 175 30 -45 3.71 0.6071
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 Apr 29 09:13:01 CDT 2009