2009/04/06 03:56:45 42.336 13.387 10. 3.90 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/06 03:56:45:0 42.34 13.39 10.0 3.9 Italy
Stations used:
IV.AOI IV.ARCI IV.ASQU IV.BSSO IV.CAFE IV.CAFI IV.CAFR
IV.CERA IV.CERT IV.CESI IV.CING IV.FDMO IV.FSSB IV.GIUL
IV.INTR IV.LATE IV.LPEL IV.MA9 IV.MAON IV.MGAB IV.MIDA
IV.MODR IV.MRB1 IV.MTCE IV.MURB IV.NRCA IV.OFFI IV.PESA
IV.PIEI IV.RMP IV.RNI2 IV.ROM9 IV.RSM IV.SGG IV.SGRT
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 = 3.31e+22 dyne-cm
Mw = 4.28
Z = 10 km
Plane Strike Dip Rake
NP1 314 68 -118
NP2 190 35 -40
Principal Axes:
Axis Value Plunge Azimuth
T 3.31e+22 19 65
N 0.00e+00 26 326
P -3.31e+22 57 186
Moment Tensor: (dyne-cm)
Component Value
Mxx -4.37e+21
Mxy 1.03e+22
Mxz 1.92e+22
Myy 2.44e+22
Myz 1.08e+22
Mzz -2.00e+22
-------#######
-------###############
--------####################
###----#######################
########--########################
#######-------######################
########----------############### ##
########-------------############# T ###
#######----------------########### ###
########------------------################
#######---------------------##############
#######----------------------#############
#######------------------------###########
######-------------------------#########
#######----------- -----------########
######----------- P ------------######
######---------- -------------####
######-------------------------###
#####-------------------------
#####-----------------------
####------------------
##------------
Global CMT Convention Moment Tensor:
R T P
-2.00e+22 1.92e+22 -1.08e+22
1.92e+22 -4.37e+21 -1.03e+22
-1.08e+22 -1.03e+22 2.44e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090406035645/index.html
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STK = 190
DIP = 35
RAKE = -40
MW = 4.28
HS = 10.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/06 03:56:45:0 42.34 13.39 10.0 3.9 Italy
Stations used:
IV.AOI IV.ARCI IV.ASQU IV.BSSO IV.CAFE IV.CAFI IV.CAFR
IV.CERA IV.CERT IV.CESI IV.CING IV.FDMO IV.FSSB IV.GIUL
IV.INTR IV.LATE IV.LPEL IV.MA9 IV.MAON IV.MGAB IV.MIDA
IV.MODR IV.MRB1 IV.MTCE IV.MURB IV.NRCA IV.OFFI IV.PESA
IV.PIEI IV.RMP IV.RNI2 IV.ROM9 IV.RSM IV.SGG IV.SGRT
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 = 3.31e+22 dyne-cm
Mw = 4.28
Z = 10 km
Plane Strike Dip Rake
NP1 314 68 -118
NP2 190 35 -40
Principal Axes:
Axis Value Plunge Azimuth
T 3.31e+22 19 65
N 0.00e+00 26 326
P -3.31e+22 57 186
Moment Tensor: (dyne-cm)
Component Value
Mxx -4.37e+21
Mxy 1.03e+22
Mxz 1.92e+22
Myy 2.44e+22
Myz 1.08e+22
Mzz -2.00e+22
-------#######
-------###############
--------####################
###----#######################
########--########################
#######-------######################
########----------############### ##
########-------------############# T ###
#######----------------########### ###
########------------------################
#######---------------------##############
#######----------------------#############
#######------------------------###########
######-------------------------#########
#######----------- -----------########
######----------- P ------------######
######---------- -------------####
######-------------------------###
#####-------------------------
#####-----------------------
####------------------
##------------
Global CMT Convention Moment Tensor:
R T P
-2.00e+22 1.92e+22 -1.08e+22
1.92e+22 -4.37e+21 -1.03e+22
-1.08e+22 -1.03e+22 2.44e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090406035645/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 0.5 150 50 90 3.94 0.2565
WVFGRD96 1.0 290 55 30 3.88 0.2016
WVFGRD96 2.0 325 40 -95 4.09 0.2506
WVFGRD96 3.0 130 75 70 4.12 0.2577
WVFGRD96 4.0 135 75 70 4.14 0.3102
WVFGRD96 5.0 140 75 70 4.16 0.3383
WVFGRD96 6.0 200 30 -25 4.15 0.3504
WVFGRD96 7.0 200 30 -30 4.17 0.3653
WVFGRD96 8.0 190 30 -40 4.25 0.3790
WVFGRD96 9.0 190 30 -40 4.27 0.3866
WVFGRD96 10.0 190 35 -40 4.28 0.3876
WVFGRD96 11.0 185 35 -45 4.29 0.3860
WVFGRD96 12.0 180 35 -50 4.30 0.3805
WVFGRD96 13.0 185 40 -40 4.31 0.3725
WVFGRD96 14.0 180 45 -45 4.33 0.3654
WVFGRD96 15.0 180 50 -40 4.34 0.3587
WVFGRD96 16.0 185 55 -30 4.35 0.3513
WVFGRD96 17.0 180 55 -40 4.36 0.3437
WVFGRD96 18.0 175 55 -45 4.37 0.3367
WVFGRD96 19.0 175 55 -45 4.38 0.3310
WVFGRD96 20.0 175 55 -45 4.39 0.3243
WVFGRD96 21.0 175 60 -45 4.41 0.3213
WVFGRD96 22.0 175 60 -45 4.42 0.3153
WVFGRD96 23.0 175 60 -45 4.43 0.3084
WVFGRD96 24.0 180 60 -40 4.43 0.3008
WVFGRD96 25.0 180 60 -40 4.44 0.2935
WVFGRD96 26.0 180 60 -40 4.45 0.2858
WVFGRD96 27.0 180 60 -40 4.45 0.2778
WVFGRD96 28.0 0 50 -40 4.44 0.2699
WVFGRD96 29.0 0 50 -40 4.45 0.2626
The best solution is
WVFGRD96 10.0 190 35 -40 4.28 0.3876
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 07:11:43 CDT 2009