2009/04/30 09:13:55 42.355 13.425 9.1 3.1 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/30 09:13:55:0 42.35 13.43 9.1 3.1 Italy
Stations used:
IV.FAGN IV.FIAM IV.GUAR IV.GUMA IV.MNS IV.OFFI IV.TERO
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 3.13e+20 dyne-cm
Mw = 2.93
Z = 2 km
Plane Strike Dip Rake
NP1 306 52 -117
NP2 165 45 -60
Principal Axes:
Axis Value Plunge Azimuth
T 3.13e+20 4 54
N 0.00e+00 21 323
P -3.13e+20 69 154
Moment Tensor: (dyne-cm)
Component Value
Mxx 7.34e+19
Mxy 1.63e+20
Mxz 1.07e+20
Myy 1.97e+20
Myz -2.86e+19
Mzz -2.71e+20
-#############
---###################
-----#######################
-----#########################
######--------################## T
#######-------------#############
########----------------##############
########-------------------#############
########---------------------###########
#########-----------------------##########
#########------------------------#########
##########-------------------------#######
##########------------ -----------######
##########----------- P ------------####
##########----------- ------------####
##########--------------------------##
##########-------------------------#
##########------------------------
##########--------------------
###########-----------------
##########------------
##########----
Global CMT Convention Moment Tensor:
R T P
-2.71e+20 1.07e+20 2.86e+19
1.07e+20 7.34e+19 -1.63e+20
2.86e+19 -1.63e+20 1.97e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090430091355/index.html
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STK = 165
DIP = 45
RAKE = -60
MW = 2.93
HS = 2.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/30 09:13:55:0 42.35 13.43 9.1 3.1 Italy
Stations used:
IV.FAGN IV.FIAM IV.GUAR IV.GUMA IV.MNS IV.OFFI IV.TERO
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 3.13e+20 dyne-cm
Mw = 2.93
Z = 2 km
Plane Strike Dip Rake
NP1 306 52 -117
NP2 165 45 -60
Principal Axes:
Axis Value Plunge Azimuth
T 3.13e+20 4 54
N 0.00e+00 21 323
P -3.13e+20 69 154
Moment Tensor: (dyne-cm)
Component Value
Mxx 7.34e+19
Mxy 1.63e+20
Mxz 1.07e+20
Myy 1.97e+20
Myz -2.86e+19
Mzz -2.71e+20
-#############
---###################
-----#######################
-----#########################
######--------################## T
#######-------------#############
########----------------##############
########-------------------#############
########---------------------###########
#########-----------------------##########
#########------------------------#########
##########-------------------------#######
##########------------ -----------######
##########----------- P ------------####
##########----------- ------------####
##########--------------------------##
##########-------------------------#
##########------------------------
##########--------------------
###########-----------------
##########------------
##########----
Global CMT Convention Moment Tensor:
R T P
-2.71e+20 1.07e+20 2.86e+19
1.07e+20 7.34e+19 -1.63e+20
2.86e+19 -1.63e+20 1.97e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090430091355/index.html
|
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 1.0 350 55 -55 2.85 0.3615
WVFGRD96 2.0 165 45 -60 2.93 0.3914
WVFGRD96 3.0 175 50 -45 2.93 0.3831
WVFGRD96 4.0 185 60 -30 2.93 0.3694
WVFGRD96 5.0 180 55 -35 2.98 0.3537
WVFGRD96 6.0 185 65 -25 2.96 0.3299
WVFGRD96 7.0 15 75 25 2.97 0.3233
WVFGRD96 8.0 15 75 20 2.97 0.3187
WVFGRD96 9.0 185 65 -30 3.00 0.3114
WVFGRD96 10.0 185 65 -30 3.01 0.3083
WVFGRD96 11.0 185 65 -30 3.02 0.3056
WVFGRD96 12.0 185 65 -30 3.03 0.3026
WVFGRD96 13.0 190 65 -30 3.05 0.2991
WVFGRD96 14.0 190 65 -30 3.06 0.2962
WVFGRD96 15.0 185 60 -35 3.08 0.2915
WVFGRD96 16.0 185 60 -35 3.09 0.2874
WVFGRD96 17.0 190 65 -30 3.09 0.2828
WVFGRD96 18.0 190 60 -30 3.10 0.2796
WVFGRD96 19.0 190 60 -30 3.10 0.2779
WVFGRD96 20.0 190 60 -30 3.11 0.2769
WVFGRD96 21.0 190 55 -30 3.13 0.2758
WVFGRD96 22.0 195 60 -25 3.13 0.2760
WVFGRD96 23.0 10 65 -40 3.16 0.2728
WVFGRD96 24.0 10 70 -40 3.16 0.2738
WVFGRD96 25.0 10 70 -40 3.17 0.2731
WVFGRD96 26.0 10 70 -35 3.18 0.2703
WVFGRD96 27.0 15 75 -35 3.19 0.2676
WVFGRD96 28.0 15 75 -30 3.19 0.2647
WVFGRD96 29.0 205 55 10 3.20 0.2635
The best solution is
WVFGRD96 2.0 165 45 -60 2.93 0.3914
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 May 17 12:10:27 CDT 2010