2009/04/03 04:44:42 42.327 13.358 9.40 3.00 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/03 04:44:42:0 42.33 13.36 9.4 3.0 Italy
Stations used:
IV.FAGN IV.FIAM IV.INTR IV.LPEL IV.MTCE IV.RMP
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 6.68e+20 dyne-cm
Mw = 3.15
Z = 11 km
Plane Strike Dip Rake
NP1 303 57 -130
NP2 180 50 -45
Principal Axes:
Axis Value Plunge Azimuth
T 6.68e+20 4 60
N 0.00e+00 33 327
P -6.68e+20 57 156
Moment Tensor: (dyne-cm)
Component Value
Mxx -6.33e+13
Mxy 3.62e+20
Mxz 3.04e+20
Myy 4.65e+20
Myz -8.21e+19
Mzz -4.65e+20
-----#########
-------###############
---------###################
--------######################
---#####-########################
##########------################## T
##########-----------##############
###########--------------###############
##########------------------############
###########--------------------###########
###########----------------------#########
###########-----------------------########
###########------------------------#######
##########-------------------------#####
###########----------- -----------####
##########----------- P ------------##
##########---------- ------------#
#########-------------------------
########----------------------
#########-------------------
#######---------------
#####---------
Global CMT Convention Moment Tensor:
R T P
-4.65e+20 3.04e+20 8.21e+19
3.04e+20 -6.33e+13 -3.62e+20
8.21e+19 -3.62e+20 4.65e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090403044442/index.html
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STK = 180
DIP = 50
RAKE = -45
MW = 3.15
HS = 11.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/03 04:44:42:0 42.33 13.36 9.4 3.0 Italy
Stations used:
IV.FAGN IV.FIAM IV.INTR IV.LPEL IV.MTCE IV.RMP
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 6.68e+20 dyne-cm
Mw = 3.15
Z = 11 km
Plane Strike Dip Rake
NP1 303 57 -130
NP2 180 50 -45
Principal Axes:
Axis Value Plunge Azimuth
T 6.68e+20 4 60
N 0.00e+00 33 327
P -6.68e+20 57 156
Moment Tensor: (dyne-cm)
Component Value
Mxx -6.33e+13
Mxy 3.62e+20
Mxz 3.04e+20
Myy 4.65e+20
Myz -8.21e+19
Mzz -4.65e+20
-----#########
-------###############
---------###################
--------######################
---#####-########################
##########------################## T
##########-----------##############
###########--------------###############
##########------------------############
###########--------------------###########
###########----------------------#########
###########-----------------------########
###########------------------------#######
##########-------------------------#####
###########----------- -----------####
##########----------- P ------------##
##########---------- ------------#
#########-------------------------
########----------------------
#########-------------------
#######---------------
#####---------
Global CMT Convention Moment Tensor:
R T P
-4.65e+20 3.04e+20 8.21e+19
3.04e+20 -6.33e+13 -3.62e+20
8.21e+19 -3.62e+20 4.65e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090403044442/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 0.5 270 40 85 2.93 0.4033
WVFGRD96 1.0 325 45 85 2.88 0.3556
WVFGRD96 2.0 10 85 -25 2.92 0.3801
WVFGRD96 3.0 245 25 25 3.00 0.4655
WVFGRD96 4.0 240 30 30 3.00 0.5239
WVFGRD96 5.0 230 20 45 3.17 0.5745
WVFGRD96 6.0 225 20 40 3.17 0.6080
WVFGRD96 7.0 215 25 35 3.18 0.6255
WVFGRD96 8.0 175 50 -55 3.12 0.6692
WVFGRD96 9.0 175 50 -50 3.13 0.7001
WVFGRD96 10.0 175 50 -50 3.15 0.7161
WVFGRD96 11.0 180 50 -45 3.15 0.7214
WVFGRD96 12.0 180 50 -45 3.16 0.7181
WVFGRD96 13.0 185 50 -40 3.17 0.7091
WVFGRD96 14.0 180 45 -45 3.18 0.6933
WVFGRD96 15.0 180 45 -45 3.21 0.6801
WVFGRD96 16.0 185 45 -35 3.21 0.6639
WVFGRD96 17.0 185 45 -35 3.22 0.6449
WVFGRD96 18.0 185 45 -35 3.23 0.6226
WVFGRD96 19.0 190 45 -30 3.23 0.6007
WVFGRD96 20.0 190 45 -30 3.24 0.5787
WVFGRD96 21.0 190 45 -30 3.24 0.5572
WVFGRD96 22.0 195 45 -30 3.24 0.5422
WVFGRD96 23.0 195 45 -30 3.25 0.5287
WVFGRD96 24.0 190 45 -35 3.26 0.5176
WVFGRD96 25.0 195 50 -30 3.26 0.5082
WVFGRD96 26.0 195 50 -30 3.27 0.4995
WVFGRD96 27.0 195 50 -30 3.28 0.4886
WVFGRD96 28.0 195 50 -30 3.29 0.4770
WVFGRD96 29.0 200 50 -30 3.30 0.4672
The best solution is
WVFGRD96 11.0 180 50 -45 3.15 0.7214
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=Sun Aug 23 11:22:55 CDT 2009