2009/04/08 23:18:06 42.391 13.325 10.8 3.30 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/08 23:18:06:0 42.39 13.32 10.8 3.3 Italy
Stations used:
IV.ASSB IV.BSSO IV.CAFR IV.CERT IV.CESX IV.CING IV.FDMO
IV.FIAM IV.INTR IV.LATE IV.MGAB IV.MIDA IV.MNS IV.MTCE
IV.NRCA IV.OFFI IV.SACS IV.TERO
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 2.24e+21 dyne-cm
Mw = 3.50
Z = 6 km
Plane Strike Dip Rake
NP1 133 56 -113
NP2 350 40 -60
Principal Axes:
Axis Value Plunge Azimuth
T 2.24e+21 9 239
N 0.00e+00 19 146
P -2.24e+21 69 352
Moment Tensor: (dyne-cm)
Component Value
Mxx 3.04e+20
Mxy 1.00e+21
Mxz -9.03e+20
Myy 1.61e+21
Myz -1.83e+20
Mzz -1.91e+21
-------#######
--------------########
-------------------#########
----------------------########
##-----------------------#########
###------------------------#########
####-------------------------#########
######------------ ----------#########
######------------ P -----------########
########----------- -----------#########
#########------------------------#########
###########-----------------------########
############----------------------########
#############--------------------#######
##############------------------########
# ############---------------#######
T ##############------------#######
##################--------######
#######################--#####
#######################-----
##################----
############--
Global CMT Convention Moment Tensor:
R T P
-1.91e+21 -9.03e+20 1.83e+20
-9.03e+20 3.04e+20 -1.00e+21
1.83e+20 -1.00e+21 1.61e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090408231806/index.html
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STK = 350
DIP = 40
RAKE = -60
MW = 3.50
HS = 6.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/08 23:18:06:0 42.39 13.32 10.8 3.3 Italy
Stations used:
IV.ASSB IV.BSSO IV.CAFR IV.CERT IV.CESX IV.CING IV.FDMO
IV.FIAM IV.INTR IV.LATE IV.MGAB IV.MIDA IV.MNS IV.MTCE
IV.NRCA IV.OFFI IV.SACS IV.TERO
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 2.24e+21 dyne-cm
Mw = 3.50
Z = 6 km
Plane Strike Dip Rake
NP1 133 56 -113
NP2 350 40 -60
Principal Axes:
Axis Value Plunge Azimuth
T 2.24e+21 9 239
N 0.00e+00 19 146
P -2.24e+21 69 352
Moment Tensor: (dyne-cm)
Component Value
Mxx 3.04e+20
Mxy 1.00e+21
Mxz -9.03e+20
Myy 1.61e+21
Myz -1.83e+20
Mzz -1.91e+21
-------#######
--------------########
-------------------#########
----------------------########
##-----------------------#########
###------------------------#########
####-------------------------#########
######------------ ----------#########
######------------ P -----------########
########----------- -----------#########
#########------------------------#########
###########-----------------------########
############----------------------########
#############--------------------#######
##############------------------########
# ############---------------#######
T ##############------------#######
##################--------######
#######################--#####
#######################-----
##################----
############--
Global CMT Convention Moment Tensor:
R T P
-1.91e+21 -9.03e+20 1.83e+20
-9.03e+20 3.04e+20 -1.00e+21
1.83e+20 -1.00e+21 1.61e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090408231806/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 0.5 190 60 -30 3.17 0.3319
WVFGRD96 1.0 190 60 -25 3.18 0.3322
WVFGRD96 2.0 15 35 -15 3.32 0.3753
WVFGRD96 3.0 10 40 -25 3.34 0.4442
WVFGRD96 4.0 -5 40 -55 3.40 0.5045
WVFGRD96 5.0 350 35 -60 3.49 0.5698
WVFGRD96 6.0 350 40 -60 3.50 0.6084
WVFGRD96 7.0 350 40 -60 3.50 0.6064
WVFGRD96 8.0 5 50 -35 3.46 0.5769
WVFGRD96 9.0 5 55 -30 3.46 0.5632
WVFGRD96 10.0 10 60 -25 3.47 0.5463
WVFGRD96 11.0 10 60 -25 3.48 0.5288
WVFGRD96 12.0 10 65 -25 3.49 0.5100
WVFGRD96 13.0 10 65 -25 3.50 0.4897
WVFGRD96 14.0 10 65 -20 3.51 0.4674
WVFGRD96 15.0 10 65 -25 3.52 0.4539
WVFGRD96 16.0 10 65 -25 3.53 0.4357
WVFGRD96 17.0 10 70 -20 3.53 0.4200
WVFGRD96 18.0 10 70 -20 3.54 0.4062
WVFGRD96 19.0 10 70 -20 3.55 0.3942
WVFGRD96 20.0 10 70 -20 3.55 0.3848
WVFGRD96 21.0 10 70 -20 3.56 0.3770
WVFGRD96 22.0 10 75 -20 3.57 0.3719
WVFGRD96 23.0 10 75 -15 3.57 0.3678
WVFGRD96 24.0 10 70 -20 3.59 0.3646
WVFGRD96 25.0 10 70 -20 3.60 0.3633
WVFGRD96 26.0 15 65 -15 3.60 0.3619
WVFGRD96 27.0 15 65 -15 3.62 0.3607
WVFGRD96 28.0 15 65 -15 3.63 0.3590
WVFGRD96 29.0 15 65 -15 3.65 0.3582
The best solution is
WVFGRD96 6.0 350 40 -60 3.50 0.6084
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 11:55:39 CDT 2009