2009/04/19 12:39:50 44.727 7.845 40.2 3.90 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/19 12:39:50:0 44.73 7.84 40.2 3.9 Italy
Stations used:
IG.FINB IG.LSD IG.PCP IG.PZZ IG.RORO IV.DOI IV.MONC IV.QLNO
IV.RSP IV.STV
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 = 33 km
Plane Strike Dip Rake
NP1 165 80 -30
NP2 261 61 -168
Principal Axes:
Axis Value Plunge Azimuth
T 4.32e+21 13 216
N 0.00e+00 59 328
P -4.32e+21 28 119
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.89e+21
Mxy 3.37e+21
Mxz 1.02e+20
Myy -1.15e+21
Myz -2.13e+21
Mzz -7.38e+20
--############
------################
---------###################
----------####################
------------######################
-------------#######################
---------------#######################
---------------#-------------------#####
---------#######-----------------------#
-------###########------------------------
----##############------------------------
--#################-----------------------
-##################-----------------------
###################------------- -----
###################------------- P -----
###################------------ ----
###################-----------------
#### ###########----------------
## T ############-------------
# #############-----------
###############-------
############--
Global CMT Convention Moment Tensor:
R T P
-7.38e+20 1.02e+20 2.13e+21
1.02e+20 1.89e+21 -3.37e+21
2.13e+21 -3.37e+21 -1.15e+21
Details of the solution is found at
http://www.eas.slu.edu/Earthquake_Center/MECH.NA/20090419123950/index.html
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STK = 165
DIP = 80
RAKE = -30
MW = 3.69
HS = 33.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/19 12:39:50:0 44.73 7.84 40.2 3.9 Italy
Stations used:
IG.FINB IG.LSD IG.PCP IG.PZZ IG.RORO IV.DOI IV.MONC IV.QLNO
IV.RSP IV.STV
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 = 33 km
Plane Strike Dip Rake
NP1 165 80 -30
NP2 261 61 -168
Principal Axes:
Axis Value Plunge Azimuth
T 4.32e+21 13 216
N 0.00e+00 59 328
P -4.32e+21 28 119
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.89e+21
Mxy 3.37e+21
Mxz 1.02e+20
Myy -1.15e+21
Myz -2.13e+21
Mzz -7.38e+20
--############
------################
---------###################
----------####################
------------######################
-------------#######################
---------------#######################
---------------#-------------------#####
---------#######-----------------------#
-------###########------------------------
----##############------------------------
--#################-----------------------
-##################-----------------------
###################------------- -----
###################------------- P -----
###################------------ ----
###################-----------------
#### ###########----------------
## T ############-------------
# #############-----------
###############-------
############--
Global CMT Convention Moment Tensor:
R T P
-7.38e+20 1.02e+20 2.13e+21
1.02e+20 1.89e+21 -3.37e+21
2.13e+21 -3.37e+21 -1.15e+21
Details of the solution is found at
http://www.eas.slu.edu/Earthquake_Center/MECH.NA/20090419123950/index.html
|
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 90 75 10 2.95 0.1830
WVFGRD96 1.0 270 75 0 2.99 0.2018
WVFGRD96 2.0 90 80 10 3.15 0.2814
WVFGRD96 3.0 90 80 10 3.23 0.3160
WVFGRD96 4.0 90 80 5 3.27 0.3314
WVFGRD96 5.0 85 75 -15 3.30 0.3354
WVFGRD96 6.0 0 85 5 3.35 0.3406
WVFGRD96 7.0 -5 90 0 3.37 0.3638
WVFGRD96 8.0 175 90 -5 3.42 0.3910
WVFGRD96 9.0 175 80 0 3.45 0.3983
WVFGRD96 10.0 175 80 -5 3.47 0.4049
WVFGRD96 11.0 175 80 -5 3.49 0.4093
WVFGRD96 12.0 175 80 -5 3.51 0.4117
WVFGRD96 13.0 175 80 -10 3.53 0.4126
WVFGRD96 14.0 170 75 -20 3.54 0.4173
WVFGRD96 15.0 170 75 -20 3.55 0.4236
WVFGRD96 16.0 170 75 -20 3.57 0.4295
WVFGRD96 17.0 165 75 -25 3.57 0.4361
WVFGRD96 18.0 165 75 -25 3.58 0.4423
WVFGRD96 19.0 165 75 -25 3.59 0.4496
WVFGRD96 20.0 165 75 -25 3.60 0.4562
WVFGRD96 21.0 165 75 -25 3.61 0.4612
WVFGRD96 22.0 165 75 -30 3.63 0.4676
WVFGRD96 23.0 165 75 -30 3.64 0.4741
WVFGRD96 24.0 165 75 -30 3.64 0.4784
WVFGRD96 25.0 165 75 -30 3.65 0.4857
WVFGRD96 26.0 165 75 -30 3.66 0.4913
WVFGRD96 27.0 165 80 -30 3.66 0.4982
WVFGRD96 28.0 165 80 -30 3.67 0.5042
WVFGRD96 29.0 165 80 -30 3.67 0.5110
WVFGRD96 30.0 165 80 -30 3.68 0.5148
WVFGRD96 31.0 165 80 -30 3.68 0.5195
WVFGRD96 32.0 165 80 -30 3.68 0.5193
WVFGRD96 33.0 165 80 -30 3.69 0.5201
WVFGRD96 34.0 165 80 -30 3.69 0.5181
WVFGRD96 35.0 165 80 -30 3.70 0.5152
WVFGRD96 36.0 165 80 -30 3.70 0.5122
WVFGRD96 37.0 165 80 -30 3.71 0.5071
WVFGRD96 38.0 165 80 -30 3.71 0.5055
WVFGRD96 39.0 165 80 -25 3.72 0.5050
WVFGRD96 40.0 165 80 -35 3.78 0.5046
The best solution is
WVFGRD96 33.0 165 80 -30 3.69 0.5201
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 componnet 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=Tue Apr 21 19:28:57 CDT 2009