2009/05/01 05:12:51 42.280 13.470 9.0 3.80 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/05/01 05:12:51:0 42.28 13.47 9.0 3.8 Italy
Stations used:
IV.AOI IV.ARVD IV.BSSO IV.CERA IV.CERT IV.CESX IV.CING
IV.FDMO IV.FIAM IV.GIUL IV.INTR IV.LPEL IV.MIDA IV.MNS
IV.MODR IV.MURB IV.NRCA IV.OFFI IV.PIEI IV.POFI IV.PTRJ
IV.RDP IV.RMP IV.SACS IV.TERO IV.TRIV IV.VAGA
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 4.32e+21 dyne-cm
Mw = 3.69
Z = 7 km
Plane Strike Dip Rake
NP1 139 79 -101
NP2 5 15 -45
Principal Axes:
Axis Value Plunge Azimuth
T 4.32e+21 34 238
N 0.00e+00 11 141
P -4.32e+21 54 36
Moment Tensor: (dyne-cm)
Component Value
Mxx -1.26e+20
Mxy 6.45e+20
Mxz -2.71e+21
Myy 1.65e+21
Myz -2.89e+21
Mzz -1.53e+21
-------------#
--------------------##
-------------------------###
##--------------------------##
#####--------------------------###
#######--------------------------###
#########------------- ----------###
############----------- P -----------###
#############---------- -----------###
###############------------------------###
#################----------------------###
##################---------------------###
####################-------------------###
###### ############----------------###
###### T #############---------------###
##### ###############------------###
########################---------###
#########################------###
##########################-###
#########################---
###################---
###########---
Global CMT Convention Moment Tensor:
R T P
-1.53e+21 -2.71e+21 2.89e+21
-2.71e+21 -1.26e+20 -6.45e+20
2.89e+21 -6.45e+20 1.65e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090501051251/index.html
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STK = 5
DIP = 15
RAKE = -45
MW = 3.69
HS = 7.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/05/01 05:12:51:0 42.28 13.47 9.0 3.8 Italy
Stations used:
IV.AOI IV.ARVD IV.BSSO IV.CERA IV.CERT IV.CESX IV.CING
IV.FDMO IV.FIAM IV.GIUL IV.INTR IV.LPEL IV.MIDA IV.MNS
IV.MODR IV.MURB IV.NRCA IV.OFFI IV.PIEI IV.POFI IV.PTRJ
IV.RDP IV.RMP IV.SACS IV.TERO IV.TRIV IV.VAGA
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 4.32e+21 dyne-cm
Mw = 3.69
Z = 7 km
Plane Strike Dip Rake
NP1 139 79 -101
NP2 5 15 -45
Principal Axes:
Axis Value Plunge Azimuth
T 4.32e+21 34 238
N 0.00e+00 11 141
P -4.32e+21 54 36
Moment Tensor: (dyne-cm)
Component Value
Mxx -1.26e+20
Mxy 6.45e+20
Mxz -2.71e+21
Myy 1.65e+21
Myz -2.89e+21
Mzz -1.53e+21
-------------#
--------------------##
-------------------------###
##--------------------------##
#####--------------------------###
#######--------------------------###
#########------------- ----------###
############----------- P -----------###
#############---------- -----------###
###############------------------------###
#################----------------------###
##################---------------------###
####################-------------------###
###### ############----------------###
###### T #############---------------###
##### ###############------------###
########################---------###
#########################------###
##########################-###
#########################---
###################---
###########---
Global CMT Convention Moment Tensor:
R T P
-1.53e+21 -2.71e+21 2.89e+21
-2.71e+21 -1.26e+20 -6.45e+20
2.89e+21 -6.45e+20 1.65e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090501051251/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 0.5 305 25 90 3.49 0.3555
WVFGRD96 1.0 125 60 95 3.47 0.3001
WVFGRD96 2.0 85 5 45 3.60 0.3237
WVFGRD96 3.0 55 10 10 3.57 0.4154
WVFGRD96 4.0 35 10 -10 3.55 0.4584
WVFGRD96 5.0 30 10 -15 3.67 0.4938
WVFGRD96 6.0 15 15 -35 3.68 0.5221
WVFGRD96 7.0 5 15 -45 3.69 0.5349
WVFGRD96 8.0 5 20 -50 3.65 0.5328
WVFGRD96 9.0 5 20 -50 3.66 0.5231
WVFGRD96 10.0 5 20 -50 3.66 0.5084
WVFGRD96 11.0 5 20 -50 3.67 0.4907
WVFGRD96 12.0 0 20 -55 3.68 0.4706
WVFGRD96 13.0 5 20 -50 3.68 0.4494
WVFGRD96 14.0 15 20 -40 3.68 0.4291
WVFGRD96 15.0 15 15 -40 3.73 0.4104
WVFGRD96 16.0 25 15 -25 3.73 0.3905
WVFGRD96 17.0 25 15 -25 3.74 0.3718
WVFGRD96 18.0 25 15 -25 3.75 0.3544
WVFGRD96 19.0 30 15 -20 3.75 0.3375
WVFGRD96 20.0 25 15 -25 3.76 0.3209
WVFGRD96 21.0 25 15 -25 3.76 0.3042
WVFGRD96 22.0 25 15 -25 3.77 0.2885
WVFGRD96 23.0 20 15 -30 3.77 0.2736
WVFGRD96 24.0 325 70 80 3.76 0.2637
WVFGRD96 25.0 325 70 80 3.77 0.2582
WVFGRD96 26.0 105 30 55 3.78 0.2540
WVFGRD96 27.0 115 40 70 3.79 0.2607
WVFGRD96 28.0 115 40 70 3.81 0.2630
WVFGRD96 29.0 115 40 70 3.82 0.2609
The best solution is
WVFGRD96 7.0 5 15 -45 3.69 0.5349
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=Fri May 1 07:22:35 CDT 2009