2009/03/29 08:43:07 41.985 14.002 8.1 3.8 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/03/29 08:43:07:9 41.99 14.00 8.1 3.8 Italy
Stations used:
IV.ARVD IV.CERA IV.CERT IV.FAGN IV.FDMO IV.FIAM IV.LPEL
IV.MTCE IV.PTRJ IV.RNI2 IV.TERO MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 7.24e+21 dyne-cm
Mw = 3.84
Z = 6 km
Plane Strike Dip Rake
NP1 320 90 -90
NP2 95 0 -135
Principal Axes:
Axis Value Plunge Azimuth
T 7.24e+21 45 50
N 0.00e+00 0 140
P -7.24e+21 45 230
Moment Tensor: (dyne-cm)
Component Value
Mxx -5.74e+14
Mxy -3.67e+14
Mxz 4.66e+21
Myy -5.98e+13
Myz 5.55e+21
Mzz 6.33e+14
##############
######################
-###########################
---###########################
-------###########################
---------###########################
------------############## #########
---------------############ T ##########
----------------########### ##########
-------------------#######################
--------------------######################
----------------------####################
-----------------------###################
---------- -----------################
---------- P ------------###############
--------- --------------############
---------------------------#########
---------------------------#######
---------------------------###
---------------------------#
----------------------
--------------
Global CMT Convention Moment Tensor:
R T P
6.33e+14 4.66e+21 -5.55e+21
4.66e+21 -5.74e+14 3.67e+14
-5.55e+21 3.67e+14 -5.98e+13
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090329084307/index.html
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STK = 320
DIP = 90
RAKE = -90
MW = 3.84
HS = 6.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/03/29 08:43:07:9 41.99 14.00 8.1 3.8 Italy
Stations used:
IV.ARVD IV.CERA IV.CERT IV.FAGN IV.FDMO IV.FIAM IV.LPEL
IV.MTCE IV.PTRJ IV.RNI2 IV.TERO MN.AQU
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 7.24e+21 dyne-cm
Mw = 3.84
Z = 6 km
Plane Strike Dip Rake
NP1 320 90 -90
NP2 95 0 -135
Principal Axes:
Axis Value Plunge Azimuth
T 7.24e+21 45 50
N 0.00e+00 0 140
P -7.24e+21 45 230
Moment Tensor: (dyne-cm)
Component Value
Mxx -5.74e+14
Mxy -3.67e+14
Mxz 4.66e+21
Myy -5.98e+13
Myz 5.55e+21
Mzz 6.33e+14
##############
######################
-###########################
---###########################
-------###########################
---------###########################
------------############## #########
---------------############ T ##########
----------------########### ##########
-------------------#######################
--------------------######################
----------------------####################
-----------------------###################
---------- -----------################
---------- P ------------###############
--------- --------------############
---------------------------#########
---------------------------#######
---------------------------###
---------------------------#
----------------------
--------------
Global CMT Convention Moment Tensor:
R T P
6.33e+14 4.66e+21 -5.55e+21
4.66e+21 -5.74e+14 3.67e+14
-5.55e+21 3.67e+14 -5.98e+13
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090329084307/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 1.0 165 50 -80 3.59 0.3203
WVFGRD96 2.0 290 10 30 3.74 0.3774
WVFGRD96 3.0 295 10 45 3.72 0.4817
WVFGRD96 4.0 200 -5 -30 3.72 0.5333
WVFGRD96 5.0 170 0 -60 3.84 0.5656
WVFGRD96 6.0 320 90 -90 3.84 0.5796
WVFGRD96 7.0 295 10 65 3.83 0.5767
WVFGRD96 8.0 295 10 65 3.78 0.5647
WVFGRD96 9.0 295 10 65 3.79 0.5480
WVFGRD96 10.0 295 10 65 3.79 0.5303
WVFGRD96 11.0 295 10 65 3.80 0.5088
WVFGRD96 12.0 295 10 65 3.80 0.4886
WVFGRD96 13.0 330 15 100 3.81 0.4681
WVFGRD96 14.0 140 75 85 3.82 0.4535
WVFGRD96 15.0 140 75 85 3.87 0.4391
WVFGRD96 16.0 330 15 100 3.88 0.4231
WVFGRD96 17.0 330 15 100 3.89 0.4055
WVFGRD96 18.0 310 15 80 3.90 0.3868
WVFGRD96 19.0 140 75 90 3.91 0.3665
WVFGRD96 20.0 140 75 90 3.92 0.3456
WVFGRD96 21.0 315 15 85 3.93 0.3271
WVFGRD96 22.0 320 20 90 3.93 0.3101
WVFGRD96 23.0 320 20 90 3.94 0.3001
WVFGRD96 24.0 140 70 90 3.94 0.2952
WVFGRD96 25.0 140 65 90 3.94 0.2955
WVFGRD96 26.0 320 50 -90 3.91 0.2897
WVFGRD96 27.0 315 45 -95 3.93 0.2938
WVFGRD96 28.0 145 45 -85 3.94 0.2968
WVFGRD96 29.0 145 45 -85 3.96 0.2952
The best solution is
WVFGRD96 6.0 320 90 -90 3.84 0.5796
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 12 07:13:05 CDT 2010