Location
2010/08/31 03:00:11 42.543 13.196 3.0 3.4 Italy
Arrival Times (from USGS)
Arrival time list
Felt Map
USGS Felt map for this earthquake
USGS Felt reports page for
Focal Mechanism
USGS/SLU Moment Tensor Solution
ENS 2010/08/31 03:00:11:0 42.54 13.20 3.0 3.4 Italy
Stations used:
IV.ARVD IV.CESI IV.CESX IV.CING IV.GUMA IV.MGAB IV.MNS
IV.OFFI IV.POFI IV.TERO MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 1.20e+21 dyne-cm
Mw = 3.32
Z = 4 km
Plane Strike Dip Rake
NP1 320 50 -60
NP2 98 48 -121
Principal Axes:
Axis Value Plunge Azimuth
T 1.20e+21 1 29
N 0.00e+00 23 120
P -1.20e+21 67 297
Moment Tensor: (dyne-cm)
Component Value
Mxx 8.77e+20
Mxy 5.85e+20
Mxz -1.80e+20
Myy 1.48e+20
Myz 3.87e+20
Mzz -1.03e+21
##############
#################### T
-------################ ##
-------------#################
-------------------###############
----------------------##############
-------------------------#############
----------------------------############
------------- -------------###########
-------------- P --------------###########
#------------- ---------------##########
###------------------------------#########
####------------------------------########
#####-----------------------------#####-
########--------------------------###---
##########----------------------------
################----------######----
###############################---
#############################-
###########################-
######################
##############
Global CMT Convention Moment Tensor:
R T P
-1.03e+21 -1.80e+20 -3.87e+20
-1.80e+20 8.77e+20 -5.85e+20
-3.87e+20 -5.85e+20 1.48e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20100831030011/index.html
|
Preferred Solution
The preferred solution from an analysis of the surface-wave spectral amplitude radiation pattern, waveform inversion and first motion observations is
STK = 320
DIP = 50
RAKE = -60
MW = 3.32
HS = 4.0
The waveform inversion is preferred.
Moment Tensor Comparison
The following compares this source inversion to others
| SLU |
INGVTDMT |
USGS/SLU Moment Tensor Solution
ENS 2010/08/31 03:00:11:0 42.54 13.20 3.0 3.4 Italy
Stations used:
IV.ARVD IV.CESI IV.CESX IV.CING IV.GUMA IV.MGAB IV.MNS
IV.OFFI IV.POFI IV.TERO MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 1.20e+21 dyne-cm
Mw = 3.32
Z = 4 km
Plane Strike Dip Rake
NP1 320 50 -60
NP2 98 48 -121
Principal Axes:
Axis Value Plunge Azimuth
T 1.20e+21 1 29
N 0.00e+00 23 120
P -1.20e+21 67 297
Moment Tensor: (dyne-cm)
Component Value
Mxx 8.77e+20
Mxy 5.85e+20
Mxz -1.80e+20
Myy 1.48e+20
Myz 3.87e+20
Mzz -1.03e+21
##############
#################### T
-------################ ##
-------------#################
-------------------###############
----------------------##############
-------------------------#############
----------------------------############
------------- -------------###########
-------------- P --------------###########
#------------- ---------------##########
###------------------------------#########
####------------------------------########
#####-----------------------------#####-
########--------------------------###---
##########----------------------------
################----------######----
###############################---
#############################-
###########################-
######################
##############
Global CMT Convention Moment Tensor:
R T P
-1.03e+21 -1.80e+20 -3.87e+20
-1.80e+20 8.77e+20 -5.85e+20
-3.87e+20 -5.85e+20 1.48e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20100831030011/index.html
|
INGV Time Domain Moment Tensor
http://earthquake.rm.ingv.it/tdmt.php
|
Waveform Inversion
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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Location of broadband stations used for waveform inversion
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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 3
The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT
WVFGRD96 1.0 335 35 -30 3.18 0.3934
WVFGRD96 2.0 330 70 -65 3.27 0.4425
WVFGRD96 3.0 320 50 -60 3.29 0.5057
WVFGRD96 4.0 320 50 -60 3.32 0.5241
WVFGRD96 5.0 315 55 -65 3.38 0.5162
WVFGRD96 6.0 315 55 -60 3.38 0.4804
WVFGRD96 7.0 330 60 -45 3.34 0.4432
WVFGRD96 8.0 350 65 30 3.31 0.4252
WVFGRD96 9.0 350 65 30 3.32 0.4160
WVFGRD96 10.0 345 70 25 3.32 0.4059
WVFGRD96 11.0 345 75 30 3.34 0.3961
WVFGRD96 12.0 345 75 25 3.34 0.3872
WVFGRD96 13.0 345 70 30 3.36 0.3776
WVFGRD96 14.0 165 80 25 3.36 0.3685
WVFGRD96 15.0 165 80 30 3.38 0.3627
WVFGRD96 16.0 165 75 35 3.40 0.3567
WVFGRD96 17.0 165 80 35 3.40 0.3524
WVFGRD96 18.0 340 90 -35 3.41 0.3479
WVFGRD96 19.0 340 90 -35 3.41 0.3469
WVFGRD96 20.0 340 90 -35 3.42 0.3458
WVFGRD96 21.0 340 90 -35 3.43 0.3457
WVFGRD96 22.0 160 90 35 3.44 0.3447
WVFGRD96 23.0 340 90 -35 3.45 0.3447
WVFGRD96 24.0 160 90 35 3.46 0.3442
WVFGRD96 25.0 160 90 35 3.47 0.3429
WVFGRD96 26.0 160 90 35 3.48 0.3420
WVFGRD96 27.0 160 90 35 3.49 0.3407
WVFGRD96 28.0 165 85 35 3.50 0.3402
WVFGRD96 29.0 340 90 -30 3.51 0.3410
The best solution is
WVFGRD96 4.0 320 50 -60 3.32 0.5241
The mechanism correspond to the best fit is
|
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Figure 1. Waveform inversion focal mechanism
|
The best fit as a function of depth is given in the following figure:
|
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Figure 2. Depth sensitivity for waveform mechanism
|
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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Figure 3. Waveform comparison for selected depth
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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.
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Discussion
Velocity Model
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
Quality Control
Here we tabulate the reasons for not using certain digital data sets
The following stations did not have a valid response files:
DATE=Tue Aug 31 07:58:37 CDT 2010
Last Changed 2010/08/31