2009/04/24 14:24:07 42.386 13.394 8.3 3.00 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/24 14:24:07:0 42.39 13.39 8.3 3.0 Italy
Stations used:
IV.ARVD IV.ASSB IV.CERT IV.CESX IV.FIAM IV.GUMA IV.MNS
IV.MTCE IV.OFFI IV.TERO
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 4.57e+20 dyne-cm
Mw = 3.04
Z = 1 km
Plane Strike Dip Rake
NP1 306 52 -102
NP2 145 40 -75
Principal Axes:
Axis Value Plunge Azimuth
T 4.57e+20 6 44
N 0.00e+00 10 313
P -4.57e+20 79 166
Moment Tensor: (dyne-cm)
Component Value
Mxx 2.15e+20
Mxy 2.30e+20
Mxz 1.18e+20
Myy 2.20e+20
Myz 1.08e+19
Mzz -4.35e+20
##############
######################
-#########################
--######################### T
###------------############## ##
####----------------################
####--------------------##############
#####----------------------#############
#####------------------------###########
#######-------------------------##########
#######---------------------------########
########------------ ------------#######
########------------ P -------------######
########----------- --------------####
#########---------------------------####
##########--------------------------##
##########-------------------------#
###########-----------------------
############------------------
##############--------------
######################
##############
Global CMT Convention Moment Tensor:
R T P
-4.35e+20 1.18e+20 -1.08e+19
1.18e+20 2.15e+20 -2.30e+20
-1.08e+19 -2.30e+20 2.20e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090424142407/index.html
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STK = 145
DIP = 40
RAKE = -75
MW = 3.04
HS = 1.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/24 14:24:07:0 42.39 13.39 8.3 3.0 Italy
Stations used:
IV.ARVD IV.ASSB IV.CERT IV.CESX IV.FIAM IV.GUMA IV.MNS
IV.MTCE IV.OFFI IV.TERO
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 4.57e+20 dyne-cm
Mw = 3.04
Z = 1 km
Plane Strike Dip Rake
NP1 306 52 -102
NP2 145 40 -75
Principal Axes:
Axis Value Plunge Azimuth
T 4.57e+20 6 44
N 0.00e+00 10 313
P -4.57e+20 79 166
Moment Tensor: (dyne-cm)
Component Value
Mxx 2.15e+20
Mxy 2.30e+20
Mxz 1.18e+20
Myy 2.20e+20
Myz 1.08e+19
Mzz -4.35e+20
##############
######################
-#########################
--######################### T
###------------############## ##
####----------------################
####--------------------##############
#####----------------------#############
#####------------------------###########
#######-------------------------##########
#######---------------------------########
########------------ ------------#######
########------------ P -------------######
########----------- --------------####
#########---------------------------####
##########--------------------------##
##########-------------------------#
###########-----------------------
############------------------
##############--------------
######################
##############
Global CMT Convention Moment Tensor:
R T P
-4.35e+20 1.18e+20 -1.08e+19
1.18e+20 2.15e+20 -2.30e+20
-1.08e+19 -2.30e+20 2.20e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090424142407/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 0.5 335 65 -70 3.01 0.3863
WVFGRD96 1.0 145 40 -75 3.04 0.4203
WVFGRD96 2.0 150 40 -70 3.10 0.4046
WVFGRD96 3.0 170 50 -35 3.06 0.3006
WVFGRD96 4.0 15 45 15 3.06 0.2784
WVFGRD96 5.0 15 35 5 3.13 0.2806
WVFGRD96 6.0 20 35 10 3.13 0.2847
WVFGRD96 7.0 25 40 10 3.14 0.2879
WVFGRD96 8.0 30 45 15 3.12 0.2904
WVFGRD96 9.0 30 45 15 3.13 0.2879
WVFGRD96 10.0 30 45 15 3.14 0.2832
WVFGRD96 11.0 30 45 10 3.15 0.2770
WVFGRD96 12.0 30 45 10 3.15 0.2701
WVFGRD96 13.0 35 40 15 3.15 0.2637
WVFGRD96 14.0 35 40 15 3.16 0.2574
WVFGRD96 15.0 40 35 20 3.19 0.2497
WVFGRD96 16.0 300 60 60 3.20 0.2509
WVFGRD96 17.0 305 60 60 3.22 0.2537
WVFGRD96 18.0 305 60 60 3.23 0.2549
WVFGRD96 19.0 305 60 60 3.24 0.2557
WVFGRD96 20.0 305 60 60 3.25 0.2580
WVFGRD96 21.0 305 60 60 3.27 0.2601
WVFGRD96 22.0 310 55 70 3.28 0.2627
WVFGRD96 23.0 310 55 70 3.29 0.2631
WVFGRD96 24.0 310 55 70 3.29 0.2594
WVFGRD96 25.0 315 55 75 3.30 0.2526
WVFGRD96 26.0 135 55 65 3.32 0.2494
WVFGRD96 27.0 130 55 65 3.33 0.2482
WVFGRD96 28.0 120 65 60 3.33 0.2465
WVFGRD96 29.0 125 60 60 3.35 0.2440
The best solution is
WVFGRD96 1.0 145 40 -75 3.04 0.4203
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 Apr 27 13:47:42 CDT 2009