2009/03/17 01:12:50 41.986 14.017 6.7 3.6 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/03/17 01:12:50:5 41.99 14.02 6.7 3.6 Italy
Stations used:
IV.CAFR IV.CERT IV.FRES IV.GUAR IV.LPEL IV.MA9 IV.MNS
IV.MSAG IV.MTCE IV.OFFI IV.POFI IV.RDP IV.RMP IV.SGRT
IV.TOLF IV.VAGA MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 3.89e+21 dyne-cm
Mw = 3.66
Z = 6 km
Plane Strike Dip Rake
NP1 315 75 -75
NP2 89 21 -134
Principal Axes:
Axis Value Plunge Azimuth
T 3.89e+21 28 33
N 0.00e+00 14 131
P -3.89e+21 57 245
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.91e+21
Mxy 9.39e+20
Mxz 2.12e+21
Myy -3.31e+19
Myz 2.49e+21
Mzz -1.88e+21
##############
######################
############################
---################### #####
--------################ T #######
------------############# ########
---------------#######################
-------------------#####################
---------------------###################
------------------------##################
-------------------------#################
------------ ------------##############-
#----------- P --------------############-
#---------- ---------------##########-
##----------------------------########--
##-----------------------------#####--
##-----------------------------##---
####--------------------------#---
####----------------------###-
########------------########
######################
##############
Global CMT Convention Moment Tensor:
R T P
-1.88e+21 2.12e+21 -2.49e+21
2.12e+21 1.91e+21 -9.39e+20
-2.49e+21 -9.39e+20 -3.31e+19
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090317011250/index.html
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STK = 315
DIP = 75
RAKE = -75
MW = 3.66
HS = 6.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/03/17 01:12:50:5 41.99 14.02 6.7 3.6 Italy
Stations used:
IV.CAFR IV.CERT IV.FRES IV.GUAR IV.LPEL IV.MA9 IV.MNS
IV.MSAG IV.MTCE IV.OFFI IV.POFI IV.RDP IV.RMP IV.SGRT
IV.TOLF IV.VAGA MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 3.89e+21 dyne-cm
Mw = 3.66
Z = 6 km
Plane Strike Dip Rake
NP1 315 75 -75
NP2 89 21 -134
Principal Axes:
Axis Value Plunge Azimuth
T 3.89e+21 28 33
N 0.00e+00 14 131
P -3.89e+21 57 245
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.91e+21
Mxy 9.39e+20
Mxz 2.12e+21
Myy -3.31e+19
Myz 2.49e+21
Mzz -1.88e+21
##############
######################
############################
---################### #####
--------################ T #######
------------############# ########
---------------#######################
-------------------#####################
---------------------###################
------------------------##################
-------------------------#################
------------ ------------##############-
#----------- P --------------############-
#---------- ---------------##########-
##----------------------------########--
##-----------------------------#####--
##-----------------------------##---
####--------------------------#---
####----------------------###-
########------------########
######################
##############
Global CMT Convention Moment Tensor:
R T P
-1.88e+21 2.12e+21 -2.49e+21
2.12e+21 1.91e+21 -9.39e+20
-2.49e+21 -9.39e+20 -3.31e+19
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090317011250/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 1.0 155 50 -80 3.43 0.3082
WVFGRD96 2.0 150 90 80 3.60 0.3263
WVFGRD96 3.0 325 85 -75 3.57 0.4151
WVFGRD96 4.0 320 80 -70 3.55 0.4509
WVFGRD96 5.0 320 80 -75 3.65 0.4702
WVFGRD96 6.0 315 75 -75 3.66 0.4753
WVFGRD96 7.0 315 75 -75 3.66 0.4669
WVFGRD96 8.0 320 75 -65 3.60 0.4500
WVFGRD96 9.0 325 80 -60 3.59 0.4341
WVFGRD96 10.0 325 80 -60 3.60 0.4162
WVFGRD96 11.0 325 80 -60 3.60 0.3964
WVFGRD96 12.0 150 90 55 3.61 0.3771
WVFGRD96 13.0 150 85 55 3.61 0.3594
WVFGRD96 14.0 265 25 40 3.63 0.3480
WVFGRD96 15.0 265 25 40 3.68 0.3386
WVFGRD96 16.0 135 75 75 3.69 0.3297
WVFGRD96 17.0 135 75 75 3.70 0.3203
WVFGRD96 18.0 135 75 75 3.71 0.3100
WVFGRD96 19.0 140 70 80 3.72 0.3008
WVFGRD96 20.0 140 70 80 3.73 0.2917
WVFGRD96 21.0 140 70 80 3.73 0.2816
WVFGRD96 22.0 135 70 75 3.75 0.2724
WVFGRD96 23.0 135 70 75 3.75 0.2637
WVFGRD96 24.0 280 30 55 3.77 0.2566
WVFGRD96 25.0 280 30 55 3.78 0.2523
WVFGRD96 26.0 285 30 65 3.79 0.2489
WVFGRD96 27.0 295 35 50 3.79 0.2506
WVFGRD96 28.0 290 40 45 3.80 0.2531
WVFGRD96 29.0 290 40 45 3.82 0.2544
The best solution is
WVFGRD96 6.0 315 75 -75 3.66 0.4753
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 May 12 07:18:20 CDT 2010