2009/07/03 23:12:55 42.276 13.403 7.7 3.20 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/07/03 23:12:55:0 42.28 13.40 7.7 3.2 Italy
Stations used:
IV.ASSB IV.BSSO IV.CERT IV.FDMO IV.FIAM IV.GUAR IV.INTR
IV.LPEL IV.MNS IV.MTCE IV.NRCA IV.OFFI IV.ROM9 IV.TERO
MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 6.24e+20 dyne-cm
Mw = 3.13
Z = 2 km
Plane Strike Dip Rake
NP1 292 63 -121
NP2 165 40 -45
Principal Axes:
Axis Value Plunge Azimuth
T 6.24e+20 13 44
N 0.00e+00 27 308
P -6.24e+20 60 157
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.71e+20
Mxy 3.54e+20
Mxz 3.46e+20
Myy 2.64e+20
Myz -1.35e+19
Mzz -4.34e+20
-#############
---###################
-----####################
-----##################### T #
------###################### ###
------##############################
-######---------######################
#######---------------##################
#######-------------------##############
########----------------------############
########-------------------------#########
#########--------------------------#######
#########----------------------------#####
########------------- -------------###
#########------------ P ---------------#
#########----------- ---------------
#########---------------------------
#########-------------------------
#########---------------------
##########------------------
#########-------------
##########----
Global CMT Convention Moment Tensor:
R T P
-4.34e+20 3.46e+20 1.35e+19
3.46e+20 1.71e+20 -3.54e+20
1.35e+19 -3.54e+20 2.64e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090703231255/index.html
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STK = 165
DIP = 40
RAKE = -45
MW = 3.13
HS = 2.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/07/03 23:12:55:0 42.28 13.40 7.7 3.2 Italy
Stations used:
IV.ASSB IV.BSSO IV.CERT IV.FDMO IV.FIAM IV.GUAR IV.INTR
IV.LPEL IV.MNS IV.MTCE IV.NRCA IV.OFFI IV.ROM9 IV.TERO
MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 6.24e+20 dyne-cm
Mw = 3.13
Z = 2 km
Plane Strike Dip Rake
NP1 292 63 -121
NP2 165 40 -45
Principal Axes:
Axis Value Plunge Azimuth
T 6.24e+20 13 44
N 0.00e+00 27 308
P -6.24e+20 60 157
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.71e+20
Mxy 3.54e+20
Mxz 3.46e+20
Myy 2.64e+20
Myz -1.35e+19
Mzz -4.34e+20
-#############
---###################
-----####################
-----##################### T #
------###################### ###
------##############################
-######---------######################
#######---------------##################
#######-------------------##############
########----------------------############
########-------------------------#########
#########--------------------------#######
#########----------------------------#####
########------------- -------------###
#########------------ P ---------------#
#########----------- ---------------
#########---------------------------
#########-------------------------
#########---------------------
##########------------------
#########-------------
##########----
Global CMT Convention Moment Tensor:
R T P
-4.34e+20 3.46e+20 1.35e+19
3.46e+20 1.71e+20 -3.54e+20
1.35e+19 -3.54e+20 2.64e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090703231255/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 0.5 175 20 -25 3.16 0.2892
WVFGRD96 1.0 170 35 -35 3.07 0.3106
WVFGRD96 2.0 165 40 -45 3.13 0.3326
WVFGRD96 3.0 160 45 -55 3.15 0.3269
WVFGRD96 4.0 150 45 -70 3.17 0.2756
WVFGRD96 5.0 160 45 -55 3.19 0.2516
WVFGRD96 6.0 165 55 -35 3.16 0.2187
WVFGRD96 7.0 25 65 40 3.16 0.2040
WVFGRD96 8.0 20 70 30 3.14 0.1988
WVFGRD96 9.0 20 70 30 3.15 0.1924
WVFGRD96 10.0 175 75 -35 3.15 0.1867
WVFGRD96 11.0 175 75 -40 3.15 0.1826
WVFGRD96 12.0 170 75 -35 3.17 0.1788
WVFGRD96 13.0 170 75 -40 3.18 0.1752
WVFGRD96 14.0 165 70 -45 3.18 0.1709
WVFGRD96 15.0 165 70 -45 3.22 0.1697
WVFGRD96 16.0 165 70 -45 3.22 0.1648
WVFGRD96 17.0 165 70 -45 3.23 0.1595
WVFGRD96 18.0 170 75 -40 3.24 0.1550
WVFGRD96 19.0 170 75 -40 3.25 0.1513
WVFGRD96 20.0 170 70 -35 3.25 0.1492
WVFGRD96 21.0 170 70 -35 3.26 0.1487
WVFGRD96 22.0 170 70 -35 3.27 0.1481
WVFGRD96 23.0 170 70 -35 3.28 0.1478
WVFGRD96 24.0 170 70 -35 3.29 0.1489
WVFGRD96 25.0 165 70 -35 3.31 0.1499
WVFGRD96 26.0 165 70 -35 3.32 0.1508
WVFGRD96 27.0 350 85 25 3.35 0.1519
WVFGRD96 28.0 355 80 30 3.36 0.1537
WVFGRD96 29.0 355 75 30 3.38 0.1556
The best solution is
WVFGRD96 2.0 165 40 -45 3.13 0.3326
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=Fri Jul 3 20:48:02 CDT 2009