2009/04/09 19:38:16 42.501 13.356 17.2 4.90 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/09 19:38:16:0 42.50 13.36 17.2 4.9 Italy
Stations used:
IV.AOI IV.ARVD IV.ASSB IV.BSSO IV.CAFI IV.CAFR IV.CERA
IV.CERT IV.CESI IV.CESX IV.CING IV.FAGN IV.FDMO IV.FSSB
IV.GIUL IV.GUAR IV.INTR IV.LATE IV.LPEL IV.MA9 IV.MGAB
IV.MNS IV.MTCE IV.MURB IV.OFFI IV.PARC IV.PIEI IV.POFI
IV.RDP IV.RNI2 IV.SGG IV.TERO IV.TRTR 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 = 3.85e+23 dyne-cm
Mw = 4.99
Z = 8 km
Plane Strike Dip Rake
NP1 160 50 -60
NP2 298 48 -121
Principal Axes:
Axis Value Plunge Azimuth
T 3.85e+23 1 229
N 0.00e+00 23 320
P -3.85e+23 67 137
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.33e+23
Mxy 2.18e+23
Mxz 9.64e+22
Myy 1.95e+23
Myz -9.66e+22
Mzz -3.28e+23
##############
---###################
-----#######################
-----#########################
----##--------####################
#######--------------###############
########-----------------#############
#########--------------------###########
#########----------------------#########
##########------------------------########
##########--------------------------######
###########--------------------------#####
###########------------- -----------####
###########------------ P -----------###
############----------- ------------##
############-------------------------#
#########------------------------
T ##########----------------------
############------------------
#############---------------
#############---------
##############
Global CMT Convention Moment Tensor:
R T P
-3.28e+23 9.64e+22 9.66e+22
9.64e+22 1.33e+23 -2.18e+23
9.66e+22 -2.18e+23 1.95e+23
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090409193816/index.html
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STK = 160
DIP = 50
RAKE = -60
MW = 4.99
HS = 8.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/09 19:38:16:0 42.50 13.36 17.2 4.9 Italy
Stations used:
IV.AOI IV.ARVD IV.ASSB IV.BSSO IV.CAFI IV.CAFR IV.CERA
IV.CERT IV.CESI IV.CESX IV.CING IV.FAGN IV.FDMO IV.FSSB
IV.GIUL IV.GUAR IV.INTR IV.LATE IV.LPEL IV.MA9 IV.MGAB
IV.MNS IV.MTCE IV.MURB IV.OFFI IV.PARC IV.PIEI IV.POFI
IV.RDP IV.RNI2 IV.SGG IV.TERO IV.TRTR 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 = 3.85e+23 dyne-cm
Mw = 4.99
Z = 8 km
Plane Strike Dip Rake
NP1 160 50 -60
NP2 298 48 -121
Principal Axes:
Axis Value Plunge Azimuth
T 3.85e+23 1 229
N 0.00e+00 23 320
P -3.85e+23 67 137
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.33e+23
Mxy 2.18e+23
Mxz 9.64e+22
Myy 1.95e+23
Myz -9.66e+22
Mzz -3.28e+23
##############
---###################
-----#######################
-----#########################
----##--------####################
#######--------------###############
########-----------------#############
#########--------------------###########
#########----------------------#########
##########------------------------########
##########--------------------------######
###########--------------------------#####
###########------------- -----------####
###########------------ P -----------###
############----------- ------------##
############-------------------------#
#########------------------------
T ##########----------------------
############------------------
#############---------------
#############---------
##############
Global CMT Convention Moment Tensor:
R T P
-3.28e+23 9.64e+22 9.66e+22
9.64e+22 1.33e+23 -2.18e+23
9.66e+22 -2.18e+23 1.95e+23
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090409193816/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 0.5 135 45 -90 4.62 0.1889
WVFGRD96 1.0 0 70 -15 4.53 0.1462
WVFGRD96 2.0 150 45 -70 4.78 0.1952
WVFGRD96 3.0 355 35 -30 4.81 0.2190
WVFGRD96 4.0 350 35 -45 4.85 0.2536
WVFGRD96 5.0 335 30 -70 4.88 0.2742
WVFGRD96 6.0 165 40 -50 4.89 0.2847
WVFGRD96 7.0 165 50 -50 4.90 0.2885
WVFGRD96 8.0 160 50 -60 4.99 0.3046
WVFGRD96 9.0 165 55 -50 4.99 0.3023
WVFGRD96 10.0 170 60 -45 5.00 0.2966
WVFGRD96 11.0 175 65 -35 5.00 0.2903
WVFGRD96 12.0 175 70 -35 5.02 0.2840
WVFGRD96 13.0 5 70 15 5.02 0.2762
WVFGRD96 14.0 5 70 10 5.03 0.2693
WVFGRD96 15.0 0 70 -15 5.04 0.2630
WVFGRD96 16.0 0 70 -10 5.05 0.2569
WVFGRD96 17.0 5 75 5 5.06 0.2500
WVFGRD96 18.0 5 75 10 5.07 0.2444
WVFGRD96 19.0 5 75 10 5.08 0.2392
WVFGRD96 20.0 5 75 10 5.09 0.2344
WVFGRD96 21.0 5 75 10 5.10 0.2289
WVFGRD96 22.0 15 65 15 5.09 0.2239
WVFGRD96 23.0 15 65 15 5.10 0.2196
WVFGRD96 24.0 15 60 10 5.10 0.2156
WVFGRD96 25.0 15 60 10 5.11 0.2116
WVFGRD96 26.0 15 60 10 5.12 0.2075
WVFGRD96 27.0 15 60 10 5.12 0.2035
WVFGRD96 28.0 15 60 10 5.13 0.1995
WVFGRD96 29.0 15 60 10 5.13 0.1957
The best solution is
WVFGRD96 8.0 160 50 -60 4.99 0.3046
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 17:42:42 CDT 2009