2009/04/10 03:22:22 42.470 13.417 9.4 3.70 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/10 03:22:22:0 42.47 13.42 9.4 3.7 Italy
Stations used:
IV.CAFR IV.CERA IV.CESI IV.CESX IV.CING IV.FAGN IV.FDMO
IV.FIAM IV.GUAR IV.INTR IV.LPEL IV.MGAB IV.MIDA IV.MNS
IV.MTCE IV.NRCA IV.OFFI IV.POFI IV.RNI2 IV.TERO IV.TRTR
MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 4.03e+21 dyne-cm
Mw = 3.67
Z = 4 km
Plane Strike Dip Rake
NP1 294 47 -105
NP2 135 45 -75
Principal Axes:
Axis Value Plunge Azimuth
T 4.03e+21 1 34
N 0.00e+00 11 304
P -4.03e+21 79 130
Moment Tensor: (dyne-cm)
Component Value
Mxx 2.68e+21
Mxy 1.94e+21
Mxz 5.21e+20
Myy 1.21e+21
Myz -5.21e+20
Mzz -3.89e+21
##############
#################### T
####################### ##
##############################
--####--------####################
----------------------##############
###-----------------------############
#####-------------------------##########
#####---------------------------########
######-----------------------------#######
#######-----------------------------######
########--------------- ------------####
#########-------------- P -------------###
#########------------- -------------##
###########----------------------------#
###########---------------------------
#############-----------------------
##############--------------------
################--------------
############################
######################
##############
Global CMT Convention Moment Tensor:
R T P
-3.89e+21 5.21e+20 5.21e+20
5.21e+20 2.68e+21 -1.94e+21
5.21e+20 -1.94e+21 1.21e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090410032222/index.html
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STK = 135
DIP = 45
RAKE = -75
MW = 3.67
HS = 4.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/10 03:22:22:0 42.47 13.42 9.4 3.7 Italy
Stations used:
IV.CAFR IV.CERA IV.CESI IV.CESX IV.CING IV.FAGN IV.FDMO
IV.FIAM IV.GUAR IV.INTR IV.LPEL IV.MGAB IV.MIDA IV.MNS
IV.MTCE IV.NRCA IV.OFFI IV.POFI IV.RNI2 IV.TERO IV.TRTR
MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 4.03e+21 dyne-cm
Mw = 3.67
Z = 4 km
Plane Strike Dip Rake
NP1 294 47 -105
NP2 135 45 -75
Principal Axes:
Axis Value Plunge Azimuth
T 4.03e+21 1 34
N 0.00e+00 11 304
P -4.03e+21 79 130
Moment Tensor: (dyne-cm)
Component Value
Mxx 2.68e+21
Mxy 1.94e+21
Mxz 5.21e+20
Myy 1.21e+21
Myz -5.21e+20
Mzz -3.89e+21
##############
#################### T
####################### ##
##############################
--####--------####################
----------------------##############
###-----------------------############
#####-------------------------##########
#####---------------------------########
######-----------------------------#######
#######-----------------------------######
########--------------- ------------####
#########-------------- P -------------###
#########------------- -------------##
###########----------------------------#
###########---------------------------
#############-----------------------
##############--------------------
################--------------
############################
######################
##############
Global CMT Convention Moment Tensor:
R T P
-3.89e+21 5.21e+20 5.21e+20
5.21e+20 2.68e+21 -1.94e+21
5.21e+20 -1.94e+21 1.21e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090410032222/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 0.5 130 35 -75 3.38 0.2468
WVFGRD96 1.0 160 55 -30 3.34 0.2351
WVFGRD96 2.0 145 40 -55 3.54 0.3066
WVFGRD96 3.0 305 45 -90 3.64 0.3999
WVFGRD96 4.0 135 45 -75 3.67 0.4350
WVFGRD96 5.0 155 55 -50 3.66 0.4237
WVFGRD96 6.0 160 55 -40 3.66 0.4141
WVFGRD96 7.0 165 65 -30 3.67 0.3990
WVFGRD96 8.0 160 55 -40 3.74 0.3930
WVFGRD96 9.0 165 65 -30 3.73 0.3708
WVFGRD96 10.0 170 70 -20 3.74 0.3514
WVFGRD96 11.0 170 70 -20 3.75 0.3315
WVFGRD96 12.0 170 70 -20 3.76 0.3130
WVFGRD96 13.0 170 70 -20 3.77 0.2967
WVFGRD96 14.0 180 65 35 3.77 0.2863
WVFGRD96 15.0 180 65 35 3.78 0.2773
WVFGRD96 16.0 180 65 35 3.78 0.2691
WVFGRD96 17.0 180 65 35 3.79 0.2607
WVFGRD96 18.0 155 75 60 3.78 0.2533
WVFGRD96 19.0 155 75 60 3.79 0.2490
WVFGRD96 20.0 150 75 60 3.80 0.2454
WVFGRD96 21.0 150 75 60 3.82 0.2412
WVFGRD96 22.0 150 75 60 3.83 0.2369
WVFGRD96 23.0 155 75 65 3.84 0.2329
WVFGRD96 24.0 155 75 65 3.85 0.2293
WVFGRD96 25.0 285 25 45 3.87 0.2288
WVFGRD96 26.0 285 25 45 3.87 0.2261
WVFGRD96 27.0 320 85 -60 3.87 0.2254
WVFGRD96 28.0 315 80 -65 3.89 0.2259
WVFGRD96 29.0 315 80 -65 3.90 0.2263
The best solution is
WVFGRD96 4.0 135 45 -75 3.67 0.4350
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 15:23:32 CDT 2009