2009/06/23 00:41:56 42.441 13.369 15.6 3.80 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/06/23 00:41:56:0 42.44 13.37 15.6 3.8 Italy
Stations used:
IV.AOI IV.ASSB IV.BSSO IV.CERA IV.CERT IV.CESI IV.FDMO
IV.FIAM IV.FSSB IV.GUAR IV.GUMA IV.LPEL IV.MIDA IV.MNS
IV.MTCE IV.MURB IV.NRCA IV.OFFI IV.PIEI IV.RDP IV.RMP
IV.SACS IV.SAMA IV.TERO IV.TRIV MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 5.31e+21 dyne-cm
Mw = 3.75
Z = 10 km
Plane Strike Dip Rake
NP1 309 83 -103
NP2 190 15 -30
Principal Axes:
Axis Value Plunge Azimuth
T 5.31e+21 36 51
N 0.00e+00 13 311
P -5.31e+21 51 205
Moment Tensor: (dyne-cm)
Component Value
Mxx -3.67e+20
Mxy 8.91e+20
Mxz 3.97e+21
Myy 1.69e+21
Myz 3.04e+21
Mzz -1.33e+21
---###########
---###################
----########################
---###########################
##################################
###----#################### ######
###--------################# T #######
###------------############## ########
###--------------#######################
###------------------#####################
###--------------------###################
###----------------------#################
###------------------------###############
##--------------------------############
###------------ ------------##########
###----------- P --------------#######
##----------- ----------------####
##------------------------------##
##----------------------------
##--------------------------
##--------------------
#-------------
Global CMT Convention Moment Tensor:
R T P
-1.33e+21 3.97e+21 -3.04e+21
3.97e+21 -3.67e+20 -8.91e+20
-3.04e+21 -8.91e+20 1.69e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090623004156/index.html
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STK = 190
DIP = 15
RAKE = -30
MW = 3.75
HS = 10.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/06/23 00:41:56:0 42.44 13.37 15.6 3.8 Italy
Stations used:
IV.AOI IV.ASSB IV.BSSO IV.CERA IV.CERT IV.CESI IV.FDMO
IV.FIAM IV.FSSB IV.GUAR IV.GUMA IV.LPEL IV.MIDA IV.MNS
IV.MTCE IV.MURB IV.NRCA IV.OFFI IV.PIEI IV.RDP IV.RMP
IV.SACS IV.SAMA IV.TERO IV.TRIV MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 5.31e+21 dyne-cm
Mw = 3.75
Z = 10 km
Plane Strike Dip Rake
NP1 309 83 -103
NP2 190 15 -30
Principal Axes:
Axis Value Plunge Azimuth
T 5.31e+21 36 51
N 0.00e+00 13 311
P -5.31e+21 51 205
Moment Tensor: (dyne-cm)
Component Value
Mxx -3.67e+20
Mxy 8.91e+20
Mxz 3.97e+21
Myy 1.69e+21
Myz 3.04e+21
Mzz -1.33e+21
---###########
---###################
----########################
---###########################
##################################
###----#################### ######
###--------################# T #######
###------------############## ########
###--------------#######################
###------------------#####################
###--------------------###################
###----------------------#################
###------------------------###############
##--------------------------############
###------------ ------------##########
###----------- P --------------#######
##----------- ----------------####
##------------------------------##
##----------------------------
##--------------------------
##--------------------
#-------------
Global CMT Convention Moment Tensor:
R T P
-1.33e+21 3.97e+21 -3.04e+21
3.97e+21 -3.67e+20 -8.91e+20
-3.04e+21 -8.91e+20 1.69e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090623004156/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 0.5 140 50 -90 3.53 0.4098
WVFGRD96 1.0 140 55 -90 3.57 0.3574
WVFGRD96 2.0 180 15 -35 3.66 0.3179
WVFGRD96 3.0 195 15 -25 3.65 0.4382
WVFGRD96 4.0 195 15 -25 3.63 0.5101
WVFGRD96 5.0 195 15 -25 3.75 0.5679
WVFGRD96 6.0 190 15 -30 3.75 0.6207
WVFGRD96 7.0 195 15 -25 3.76 0.6547
WVFGRD96 8.0 190 15 -35 3.73 0.6734
WVFGRD96 9.0 190 15 -30 3.74 0.6817
WVFGRD96 10.0 190 15 -30 3.75 0.6833
WVFGRD96 11.0 195 15 -25 3.76 0.6785
WVFGRD96 12.0 195 15 -25 3.76 0.6694
WVFGRD96 13.0 200 15 -20 3.77 0.6573
WVFGRD96 14.0 205 15 -15 3.78 0.6437
WVFGRD96 15.0 205 15 -15 3.83 0.6281
WVFGRD96 16.0 200 15 -20 3.84 0.6093
WVFGRD96 17.0 205 15 -10 3.84 0.5897
WVFGRD96 18.0 205 15 -10 3.85 0.5702
WVFGRD96 19.0 205 15 -10 3.86 0.5498
WVFGRD96 20.0 205 15 -10 3.87 0.5299
WVFGRD96 21.0 205 15 -10 3.88 0.5106
WVFGRD96 22.0 205 15 -10 3.89 0.4926
WVFGRD96 23.0 275 20 55 3.90 0.4757
WVFGRD96 24.0 280 20 60 3.91 0.4665
WVFGRD96 25.0 265 20 45 3.91 0.4610
WVFGRD96 26.0 275 20 55 3.92 0.4541
WVFGRD96 27.0 275 15 55 3.93 0.4474
WVFGRD96 28.0 270 15 55 3.93 0.4411
WVFGRD96 29.0 265 20 50 3.93 0.4351
The best solution is
WVFGRD96 10.0 190 15 -30 3.75 0.6833
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=Mon Jun 22 21:25:09 CDT 2009