2009/04/06 22:47:13 42.349 13.293 11.6 3.60 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/06 22:47:13:0 42.35 13.29 11.6 3.6 Italy
Stations used:
IV.AOI IV.ARVD IV.ASSB IV.BSSO IV.CAFR IV.CERA IV.CERT
IV.CESI IV.CING IV.FAGN IV.FDMO IV.FIAM IV.GUAR IV.INTR
IV.LATE IV.MGAB IV.MIDA IV.MNS IV.MTCE IV.OFFI IV.PIEI
IV.PTRJ IV.RDP IV.RMP IV.SGG IV.TERO IV.TOLF IV.TRIV
IV.TRTR IV.VAGA
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 3.16e+21 dyne-cm
Mw = 3.60
Z = 10 km
Plane Strike Dip Rake
NP1 113 58 -116
NP2 335 40 -55
Principal Axes:
Axis Value Plunge Azimuth
T 3.16e+21 10 221
N 0.00e+00 22 127
P -3.16e+21 66 333
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.35e+21
Mxy 1.73e+21
Mxz -1.45e+21
Myy 1.20e+21
Myz 1.80e+20
Mzz -2.55e+21
##############
----------############
----------------############
--------------------##########
------------------------##########
--------------------------##########
-----------------------------#########
#--------------- ------------#########
##-------------- P -------------########
####------------- -------------#########
######----------------------------########
########--------------------------########
##########-------------------------#######
###########-----------------------######
###############-------------------######
##################--------------#####-
###############################-----
### ########################----
# T #######################---
######################---
#####################-
##############
Global CMT Convention Moment Tensor:
R T P
-2.55e+21 -1.45e+21 -1.80e+20
-1.45e+21 1.35e+21 -1.73e+21
-1.80e+20 -1.73e+21 1.20e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090406224713/index.html
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STK = 335
DIP = 40
RAKE = -55
MW = 3.60
HS = 10.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/06 22:47:13:0 42.35 13.29 11.6 3.6 Italy
Stations used:
IV.AOI IV.ARVD IV.ASSB IV.BSSO IV.CAFR IV.CERA IV.CERT
IV.CESI IV.CING IV.FAGN IV.FDMO IV.FIAM IV.GUAR IV.INTR
IV.LATE IV.MGAB IV.MIDA IV.MNS IV.MTCE IV.OFFI IV.PIEI
IV.PTRJ IV.RDP IV.RMP IV.SGG IV.TERO IV.TOLF IV.TRIV
IV.TRTR IV.VAGA
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 3.16e+21 dyne-cm
Mw = 3.60
Z = 10 km
Plane Strike Dip Rake
NP1 113 58 -116
NP2 335 40 -55
Principal Axes:
Axis Value Plunge Azimuth
T 3.16e+21 10 221
N 0.00e+00 22 127
P -3.16e+21 66 333
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.35e+21
Mxy 1.73e+21
Mxz -1.45e+21
Myy 1.20e+21
Myz 1.80e+20
Mzz -2.55e+21
##############
----------############
----------------############
--------------------##########
------------------------##########
--------------------------##########
-----------------------------#########
#--------------- ------------#########
##-------------- P -------------########
####------------- -------------#########
######----------------------------########
########--------------------------########
##########-------------------------#######
###########-----------------------######
###############-------------------######
##################--------------#####-
###############################-----
### ########################----
# T #######################---
######################---
#####################-
##############
Global CMT Convention Moment Tensor:
R T P
-2.55e+21 -1.45e+21 -1.80e+20
-1.45e+21 1.35e+21 -1.73e+21
-1.80e+20 -1.73e+21 1.20e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090406224713/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 0.5 115 50 90 3.33 0.3101
WVFGRD96 1.0 120 45 -85 3.36 0.2715
WVFGRD96 2.0 140 40 -65 3.43 0.2591
WVFGRD96 3.0 15 20 5 3.44 0.2941
WVFGRD96 4.0 5 25 -10 3.43 0.3407
WVFGRD96 5.0 355 20 -25 3.55 0.3818
WVFGRD96 6.0 340 25 -45 3.57 0.4307
WVFGRD96 7.0 335 30 -50 3.59 0.4738
WVFGRD96 8.0 330 35 -60 3.58 0.5000
WVFGRD96 9.0 325 35 -65 3.59 0.5117
WVFGRD96 10.0 335 40 -55 3.60 0.5149
WVFGRD96 11.0 330 40 -55 3.60 0.5122
WVFGRD96 12.0 335 40 -50 3.61 0.5043
WVFGRD96 13.0 335 40 -50 3.62 0.4923
WVFGRD96 14.0 340 40 -45 3.62 0.4771
WVFGRD96 15.0 340 35 -45 3.66 0.4687
WVFGRD96 16.0 345 35 -35 3.66 0.4542
WVFGRD96 17.0 350 35 -30 3.67 0.4392
WVFGRD96 18.0 350 35 -30 3.68 0.4234
WVFGRD96 19.0 350 35 -30 3.69 0.4065
WVFGRD96 20.0 350 35 -30 3.69 0.3893
WVFGRD96 21.0 345 40 -35 3.70 0.3731
WVFGRD96 22.0 345 45 -35 3.71 0.3612
WVFGRD96 23.0 340 45 -40 3.72 0.3530
WVFGRD96 24.0 340 45 -45 3.72 0.3453
WVFGRD96 25.0 335 45 -50 3.73 0.3364
WVFGRD96 26.0 340 45 -45 3.74 0.3276
WVFGRD96 27.0 340 45 -45 3.74 0.3180
WVFGRD96 28.0 340 45 -45 3.75 0.3073
WVFGRD96 29.0 340 45 -45 3.76 0.2951
The best solution is
WVFGRD96 10.0 335 40 -55 3.60 0.5149
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 20 08:49:06 CDT 2009