2009/04/30 13:01:01 42.361 13.364 10.90 3.50 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/30 13:01:01:0 42.36 13.36 10.9 3.5 Italy
Stations used:
IV.ASSB IV.CERT IV.CESI IV.CESX IV.FAGN IV.FDMO IV.FIAM
IV.GUAR IV.GUMA IV.INTR IV.LNSS IV.LPEL IV.MIDA IV.MNS
IV.MTCE IV.NRCA IV.OFFI IV.RMP IV.TERO IV.VVLD
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 2.40e+21 dyne-cm
Mw = 3.52
Z = 7 km
Plane Strike Dip Rake
NP1 128 66 -123
NP2 5 40 -40
Principal Axes:
Axis Value Plunge Azimuth
T 2.40e+21 14 241
N 0.00e+00 29 143
P -2.40e+21 56 354
Moment Tensor: (dyne-cm)
Component Value
Mxx -1.94e+20
Mxy 1.03e+21
Mxz -1.38e+21
Myy 1.71e+21
Myz -3.89e+20
Mzz -1.52e+21
-----------###
-----------------#####
----------------------######
------------------------######
#--------------------------#######
##-------------- ----------#######
####------------- P ----------########
######------------ -----------########
#######-------------------------########
#########------------------------#########
###########----------------------#########
#############--------------------#########
###############------------------#########
################----------------########
### ############-------------#########
## T ###############----------########
# ###################-----########
##########################-#######
#######################-------
####################--------
###############-------
########------
Global CMT Convention Moment Tensor:
R T P
-1.52e+21 -1.38e+21 3.89e+20
-1.38e+21 -1.94e+20 -1.03e+21
3.89e+20 -1.03e+21 1.71e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090430130101/index.html
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STK = 5
DIP = 40
RAKE = -40
MW = 3.52
HS = 7.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/30 13:01:01:0 42.36 13.36 10.9 3.5 Italy
Stations used:
IV.ASSB IV.CERT IV.CESI IV.CESX IV.FAGN IV.FDMO IV.FIAM
IV.GUAR IV.GUMA IV.INTR IV.LNSS IV.LPEL IV.MIDA IV.MNS
IV.MTCE IV.NRCA IV.OFFI IV.RMP IV.TERO IV.VVLD
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 2.40e+21 dyne-cm
Mw = 3.52
Z = 7 km
Plane Strike Dip Rake
NP1 128 66 -123
NP2 5 40 -40
Principal Axes:
Axis Value Plunge Azimuth
T 2.40e+21 14 241
N 0.00e+00 29 143
P -2.40e+21 56 354
Moment Tensor: (dyne-cm)
Component Value
Mxx -1.94e+20
Mxy 1.03e+21
Mxz -1.38e+21
Myy 1.71e+21
Myz -3.89e+20
Mzz -1.52e+21
-----------###
-----------------#####
----------------------######
------------------------######
#--------------------------#######
##-------------- ----------#######
####------------- P ----------########
######------------ -----------########
#######-------------------------########
#########------------------------#########
###########----------------------#########
#############--------------------#########
###############------------------#########
################----------------########
### ############-------------#########
## T ###############----------########
# ###################-----########
##########################-#######
#######################-------
####################--------
###############-------
########------
Global CMT Convention Moment Tensor:
R T P
-1.52e+21 -1.38e+21 3.89e+20
-1.38e+21 -1.94e+20 -1.03e+21
3.89e+20 -1.03e+21 1.71e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090430130101/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 0.5 255 30 75 3.26 0.3408
WVFGRD96 1.0 240 35 55 3.28 0.3303
WVFGRD96 2.0 230 30 40 3.37 0.3618
WVFGRD96 3.0 15 35 -15 3.38 0.4283
WVFGRD96 4.0 15 40 -25 3.39 0.4875
WVFGRD96 5.0 10 35 -30 3.49 0.5378
WVFGRD96 6.0 0 35 -50 3.53 0.5880
WVFGRD96 7.0 5 40 -40 3.52 0.6103
WVFGRD96 8.0 5 45 -40 3.50 0.6097
WVFGRD96 9.0 5 45 -40 3.51 0.6042
WVFGRD96 10.0 5 45 -40 3.52 0.5918
WVFGRD96 11.0 10 50 -35 3.52 0.5759
WVFGRD96 12.0 10 50 -35 3.53 0.5560
WVFGRD96 13.0 10 50 -30 3.54 0.5334
WVFGRD96 14.0 15 55 -25 3.54 0.5111
WVFGRD96 15.0 10 50 -30 3.57 0.4928
WVFGRD96 16.0 20 40 -15 3.57 0.4766
WVFGRD96 17.0 20 40 -15 3.58 0.4602
WVFGRD96 18.0 20 45 -10 3.58 0.4450
WVFGRD96 19.0 20 45 -10 3.59 0.4310
WVFGRD96 20.0 20 45 -10 3.59 0.4174
WVFGRD96 21.0 25 45 -5 3.60 0.4038
WVFGRD96 22.0 30 45 10 3.60 0.3919
WVFGRD96 23.0 10 55 -30 3.62 0.3869
WVFGRD96 24.0 10 55 -30 3.63 0.3851
WVFGRD96 25.0 10 55 -30 3.64 0.3825
WVFGRD96 26.0 10 55 -30 3.64 0.3801
WVFGRD96 27.0 10 55 -30 3.65 0.3765
WVFGRD96 28.0 10 60 -30 3.66 0.3714
WVFGRD96 29.0 10 55 -30 3.67 0.3667
The best solution is
WVFGRD96 7.0 5 40 -40 3.52 0.6103
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=Sat Aug 22 20:59:37 CDT 2009