2009/06/23 08:35:08 42.462 13.347 10.7 3.50 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/06/23 08:35:08:0 42.46 13.35 10.7 3.5 Italy
Stations used:
IV.ASSB IV.CERT IV.CESI IV.CESX IV.FSSB IV.GIUL IV.GUAR
IV.GUMA IV.INTR IV.LNSS IV.LPEL IV.MNS IV.MTCE IV.OFFI
IV.RDP IV.SACS IV.TERO IV.VVLD MN.AQU
Filtering commands used:
hp c 0.05 n 3
lp c 0.20 n 3
Best Fitting Double Couple
Mo = 1.76e+21 dyne-cm
Mw = 3.43
Z = 9 km
Plane Strike Dip Rake
NP1 320 85 -70
NP2 63 21 -166
Principal Axes:
Axis Value Plunge Azimuth
T 1.76e+21 37 32
N 0.00e+00 20 138
P -1.76e+21 46 251
Moment Tensor: (dyne-cm)
Component Value
Mxx 7.08e+20
Mxy 2.45e+20
Mxz 1.01e+21
Myy -4.22e+20
Myz 1.28e+21
Mzz -2.87e+20
##############
######################
-###########################
----##########################
--------############## #########
-----------############ T ##########
-------------########### ###########
----------------#######################-
------------------#####################-
--------------------####################--
----------------------##################--
--------- -----------#################--
--------- P -------------##############---
-------- --------------############---
---------------------------##########---
---------------------------#######----
----------------------------####----
#---------------------------#-----
#-----------------------###---
####----------------#######-
######################
##############
Global CMT Convention Moment Tensor:
R T P
-2.87e+20 1.01e+21 -1.28e+21
1.01e+21 7.08e+20 -2.45e+20
-1.28e+21 -2.45e+20 -4.22e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090623083508/index.html
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STK = 320
DIP = 85
RAKE = -70
MW = 3.43
HS = 9.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/06/23 08:35:08:0 42.46 13.35 10.7 3.5 Italy
Stations used:
IV.ASSB IV.CERT IV.CESI IV.CESX IV.FSSB IV.GIUL IV.GUAR
IV.GUMA IV.INTR IV.LNSS IV.LPEL IV.MNS IV.MTCE IV.OFFI
IV.RDP IV.SACS IV.TERO IV.VVLD MN.AQU
Filtering commands used:
hp c 0.05 n 3
lp c 0.20 n 3
Best Fitting Double Couple
Mo = 1.76e+21 dyne-cm
Mw = 3.43
Z = 9 km
Plane Strike Dip Rake
NP1 320 85 -70
NP2 63 21 -166
Principal Axes:
Axis Value Plunge Azimuth
T 1.76e+21 37 32
N 0.00e+00 20 138
P -1.76e+21 46 251
Moment Tensor: (dyne-cm)
Component Value
Mxx 7.08e+20
Mxy 2.45e+20
Mxz 1.01e+21
Myy -4.22e+20
Myz 1.28e+21
Mzz -2.87e+20
##############
######################
-###########################
----##########################
--------############## #########
-----------############ T ##########
-------------########### ###########
----------------#######################-
------------------#####################-
--------------------####################--
----------------------##################--
--------- -----------#################--
--------- P -------------##############---
-------- --------------############---
---------------------------##########---
---------------------------#######----
----------------------------####----
#---------------------------#-----
#-----------------------###---
####----------------#######-
######################
##############
Global CMT Convention Moment Tensor:
R T P
-2.87e+20 1.01e+21 -1.28e+21
1.01e+21 7.08e+20 -2.45e+20
-1.28e+21 -2.45e+20 -4.22e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090623083508/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 0.05 n 3 lp c 0.20 n 3The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT
WVFGRD96 0.5 130 50 -90 3.06 0.2843
WVFGRD96 1.0 125 50 -95 3.05 0.1995
WVFGRD96 2.0 320 90 -75 3.10 0.2126
WVFGRD96 3.0 140 90 75 3.13 0.2904
WVFGRD96 4.0 140 90 75 3.15 0.3515
WVFGRD96 5.0 140 90 75 3.30 0.3972
WVFGRD96 6.0 145 90 70 3.35 0.4439
WVFGRD96 7.0 325 90 -70 3.40 0.4810
WVFGRD96 8.0 320 85 -70 3.40 0.5051
WVFGRD96 9.0 320 85 -70 3.43 0.5157
WVFGRD96 10.0 145 90 70 3.47 0.5112
WVFGRD96 11.0 320 85 -75 3.49 0.5008
WVFGRD96 12.0 140 90 75 3.51 0.4802
WVFGRD96 13.0 140 90 75 3.52 0.4521
WVFGRD96 14.0 320 90 -80 3.53 0.4217
WVFGRD96 15.0 300 5 70 3.58 0.3928
WVFGRD96 16.0 315 10 80 3.59 0.3586
WVFGRD96 17.0 295 10 65 3.59 0.3298
WVFGRD96 18.0 320 10 85 3.59 0.3083
WVFGRD96 19.0 140 75 85 3.58 0.2930
WVFGRD96 20.0 140 75 85 3.58 0.2752
WVFGRD96 21.0 315 10 80 3.59 0.2598
WVFGRD96 22.0 320 10 85 3.59 0.2535
WVFGRD96 23.0 310 15 75 3.59 0.2498
WVFGRD96 24.0 330 60 -70 3.57 0.2704
WVFGRD96 25.0 325 55 -70 3.58 0.2906
WVFGRD96 26.0 330 55 -70 3.58 0.3035
WVFGRD96 27.0 330 55 -65 3.57 0.3033
WVFGRD96 28.0 330 55 -65 3.57 0.2965
WVFGRD96 29.0 335 60 -60 3.58 0.2945
The best solution is
WVFGRD96 9.0 320 85 -70 3.43 0.5157
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 0.05 n 3 lp c 0.20 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=Tue Jun 23 08:55:15 CDT 2009