2008/12/25 03:08:29 44.556 10.309 21.9 3.90 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2008/12/25 03:08:29:8 44.56 10.31 21.9 3.9 Italy
Stations used:
IG.MAIM IG.PCP IG.RORO IG.SC2M IV.BDI IV.BOB IV.GROG
IV.MTRZ IV.PARC
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 8.32e+21 dyne-cm
Mw = 3.88
Z = 19 km
Plane Strike Dip Rake
NP1 115 60 80
NP2 314 31 107
Principal Axes:
Axis Value Plunge Azimuth
T 8.32e+21 73 0
N 0.00e+00 9 120
P -8.32e+21 14 212
Moment Tensor: (dyne-cm)
Component Value
Mxx -4.87e+21
Mxy -3.52e+21
Mxz 4.02e+21
Myy -2.23e+21
Myz 1.08e+21
Mzz 7.09e+21
--------------
----------------------
--#############-------------
####################----------
#########################---------
############################--------
###############################-------
--################# ###########-------
---################ T ############------
-----############### #############------
-------##############################-----
---------############################-----
-----------###########################----
-------------########################---
----------------#####################---
-------------------#################--
---------------------------####---##
---------------------------------#
---- -----------------------
--- P ----------------------
-------------------
--------------
Global CMT Convention Moment Tensor:
R T P
7.09e+21 4.02e+21 -1.08e+21
4.02e+21 -4.87e+21 3.52e+21
-1.08e+21 3.52e+21 -2.23e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20081225030829/index.html
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STK = 115
DIP = 60
RAKE = 80
MW = 3.88
HS = 19.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2008/12/25 03:08:29:8 44.56 10.31 21.9 3.9 Italy
Stations used:
IG.MAIM IG.PCP IG.RORO IG.SC2M IV.BDI IV.BOB IV.GROG
IV.MTRZ IV.PARC
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 8.32e+21 dyne-cm
Mw = 3.88
Z = 19 km
Plane Strike Dip Rake
NP1 115 60 80
NP2 314 31 107
Principal Axes:
Axis Value Plunge Azimuth
T 8.32e+21 73 0
N 0.00e+00 9 120
P -8.32e+21 14 212
Moment Tensor: (dyne-cm)
Component Value
Mxx -4.87e+21
Mxy -3.52e+21
Mxz 4.02e+21
Myy -2.23e+21
Myz 1.08e+21
Mzz 7.09e+21
--------------
----------------------
--#############-------------
####################----------
#########################---------
############################--------
###############################-------
--################# ###########-------
---################ T ############------
-----############### #############------
-------##############################-----
---------############################-----
-----------###########################----
-------------########################---
----------------#####################---
-------------------#################--
---------------------------####---##
---------------------------------#
---- -----------------------
--- P ----------------------
-------------------
--------------
Global CMT Convention Moment Tensor:
R T P
7.09e+21 4.02e+21 -1.08e+21
4.02e+21 -4.87e+21 3.52e+21
-1.08e+21 3.52e+21 -2.23e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20081225030829/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 0.5 130 50 90 3.45 0.1737
WVFGRD96 1.0 45 45 90 3.45 0.1793
WVFGRD96 2.0 95 45 95 3.60 0.1913
WVFGRD96 3.0 230 65 15 3.54 0.1718
WVFGRD96 4.0 230 90 30 3.55 0.1755
WVFGRD96 5.0 45 85 -40 3.63 0.1957
WVFGRD96 6.0 50 90 -40 3.64 0.2134
WVFGRD96 7.0 235 75 45 3.67 0.2372
WVFGRD96 8.0 235 75 40 3.66 0.2577
WVFGRD96 9.0 235 70 35 3.69 0.2749
WVFGRD96 10.0 235 70 35 3.71 0.2901
WVFGRD96 11.0 235 70 35 3.72 0.3019
WVFGRD96 12.0 235 70 35 3.74 0.3117
WVFGRD96 13.0 235 70 35 3.76 0.3198
WVFGRD96 14.0 235 70 35 3.77 0.3264
WVFGRD96 15.0 115 60 75 3.82 0.3359
WVFGRD96 16.0 115 60 75 3.84 0.3463
WVFGRD96 17.0 115 60 75 3.85 0.3544
WVFGRD96 18.0 115 60 75 3.87 0.3598
WVFGRD96 19.0 115 60 80 3.88 0.3617
WVFGRD96 20.0 120 55 80 3.88 0.3614
WVFGRD96 21.0 115 55 80 3.90 0.3596
WVFGRD96 22.0 120 50 85 3.90 0.3563
WVFGRD96 23.0 115 50 80 3.91 0.3507
WVFGRD96 24.0 85 50 75 3.92 0.3410
WVFGRD96 25.0 245 60 -60 3.88 0.3326
WVFGRD96 26.0 245 60 -60 3.89 0.3245
WVFGRD96 27.0 245 60 -60 3.90 0.3164
WVFGRD96 28.0 250 65 -55 3.91 0.3110
WVFGRD96 29.0 250 65 -55 3.93 0.3080
The best solution is
WVFGRD96 19.0 115 60 80 3.88 0.3617
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=Wed May 13 09:48:40 CDT 2009