Location
2008/12/23 15:24:21 44.544 10.345 22.9 5.20 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 2008/12/23 15:24:21:7 44.54 10.35 22.9 5.2 Italy
Stations used:
IV.CERT IV.MABI IV.ROVR IV.SGG MN.TRI MN.TUE NI.CGRP
NI.PALA
Filtering commands used:
hp c 0.02 n 3
lp c 0.05 n 3
Best Fitting Double Couple
Mo = 8.22e+23 dyne-cm
Mw = 5.21
Z = 22 km
Plane Strike Dip Rake
NP1 95 55 80
NP2 292 36 104
Principal Axes:
Axis Value Plunge Azimuth
T 8.22e+23 77 331
N 0.00e+00 8 101
P -8.22e+23 9 192
Moment Tensor: (dyne-cm)
Component Value
Mxx -7.35e+23
Mxy -1.81e+23
Mxz 2.83e+23
Myy -2.61e+22
Myz -5.74e+22
Mzz 7.61e+23
--------------
----------------------
----------------------------
-------#######----------------
---####################-----------
-##########################---------
###############################-------
##################################------
################# ###############-----
################## T ################-----
-################# #################----
--#####################################---
----####################################-#
------################################-#
----------########################-----#
---------------#############----------
------------------------------------
----------------------------------
------------------------------
----------------------------
------ -------------
-- P ---------
Global CMT Convention Moment Tensor:
R T P
7.61e+23 2.83e+23 5.74e+22
2.83e+23 -7.35e+23 1.81e+23
5.74e+22 1.81e+23 -2.61e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20081223152421/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 = 95
DIP = 55
RAKE = 80
MW = 5.21
HS = 22.0
The waveform inversion is preferred. I hasd to use 0.02 - 0.05 instead of the 0.02 - 0.10 frequency band
Moment Tensor Comparison
The following compares this source inversion to others
| SLU |
TDMT |
USGS/SLU Moment Tensor Solution
ENS 2008/12/23 15:24:21:7 44.54 10.35 22.9 5.2 Italy
Stations used:
IV.CERT IV.MABI IV.ROVR IV.SGG MN.TRI MN.TUE NI.CGRP
NI.PALA
Filtering commands used:
hp c 0.02 n 3
lp c 0.05 n 3
Best Fitting Double Couple
Mo = 8.22e+23 dyne-cm
Mw = 5.21
Z = 22 km
Plane Strike Dip Rake
NP1 95 55 80
NP2 292 36 104
Principal Axes:
Axis Value Plunge Azimuth
T 8.22e+23 77 331
N 0.00e+00 8 101
P -8.22e+23 9 192
Moment Tensor: (dyne-cm)
Component Value
Mxx -7.35e+23
Mxy -1.81e+23
Mxz 2.83e+23
Myy -2.61e+22
Myz -5.74e+22
Mzz 7.61e+23
--------------
----------------------
----------------------------
-------#######----------------
---####################-----------
-##########################---------
###############################-------
##################################------
################# ###############-----
################## T ################-----
-################# #################----
--#####################################---
----####################################-#
------################################-#
----------########################-----#
---------------#############----------
------------------------------------
----------------------------------
------------------------------
----------------------------
------ -------------
-- P ---------
Global CMT Convention Moment Tensor:
R T P
7.61e+23 2.83e+23 5.74e+22
2.83e+23 -7.35e+23 1.81e+23
5.74e+22 1.81e+23 -2.61e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20081223152421/index.html
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|
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 0.05 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 0.5 105 35 -90 4.91 0.3805
WVFGRD96 1.0 285 50 -90 4.94 0.3826
WVFGRD96 2.0 105 35 90 5.00 0.3710
WVFGRD96 3.0 105 40 90 5.04 0.3321
WVFGRD96 4.0 295 90 80 5.06 0.2865
WVFGRD96 5.0 290 90 85 5.16 0.3241
WVFGRD96 6.0 40 -10 20 5.13 0.3718
WVFGRD96 7.0 40 -10 20 5.13 0.4139
WVFGRD96 8.0 20 10 5 5.08 0.4519
WVFGRD96 9.0 25 10 10 5.08 0.4817
WVFGRD96 10.0 25 10 10 5.08 0.5082
WVFGRD96 11.0 25 10 10 5.08 0.5305
WVFGRD96 12.0 105 30 90 5.14 0.5589
WVFGRD96 13.0 105 50 90 5.16 0.5995
WVFGRD96 14.0 105 50 90 5.17 0.6387
WVFGRD96 15.0 105 50 90 5.19 0.6627
WVFGRD96 16.0 100 50 85 5.19 0.6888
WVFGRD96 17.0 100 50 85 5.20 0.7085
WVFGRD96 18.0 100 50 85 5.20 0.7226
WVFGRD96 19.0 100 50 85 5.20 0.7323
WVFGRD96 20.0 100 55 85 5.20 0.7386
WVFGRD96 21.0 100 55 85 5.20 0.7421
WVFGRD96 22.0 95 55 80 5.21 0.7429
WVFGRD96 23.0 95 55 80 5.21 0.7414
WVFGRD96 24.0 95 55 80 5.22 0.7377
WVFGRD96 25.0 95 55 80 5.23 0.7319
WVFGRD96 26.0 95 55 75 5.24 0.7247
WVFGRD96 27.0 95 60 75 5.24 0.7173
WVFGRD96 28.0 95 60 75 5.25 0.7082
WVFGRD96 29.0 95 60 75 5.26 0.6982
The best solution is
WVFGRD96 22.0 95 55 80 5.21 0.7429
The mechanism correspond to the best fit is
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Figure 1. Waveform inversion focal mechanism
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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
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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 0.05 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=Wed May 13 10:22:59 CDT 2009
Last Changed 2008/12/23