2012/06/27 01:14:20 37.001 15.034 3.0 3.7 Italy
SLU Moment Tensor Solution
ENS 2012/06/27 01:14:20:0 37.00 15.03 3.0 3.7 Italy
Stations used:
IV.ECNV IV.GALF IV.HAGA IV.HCRL IV.HLNI IV.HMDC IV.RESU
IV.SSY
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 4.47e+21 dyne-cm
Mw = 3.70
Z = 5 km
Plane Strike Dip Rake
NP1 5 90 5
NP2 275 85 180
Principal Axes:
Axis Value Plunge Azimuth
T 4.47e+21 4 230
N 0.00e+00 85 5
P -4.47e+21 4 140
Moment Tensor: (dyne-cm)
Component Value
Mxx -7.73e+20
Mxy 4.38e+21
Mxz 3.39e+19
Myy 7.73e+20
Myz -3.88e+20
Mzz -3.40e+13
---------#####
-------------#########
---------------#############
----------------##############
------------------################
-------------------#################
--------------------##################
---------------------###################
--------------------####################
---------------------#####################
#####################----#################
#####################-----------------####
#####################---------------------
####################--------------------
###################---------------------
##################--------------------
#################-------------------
# ############------------------
T ############------------ -
############------------ P
#########-------------
#####---------
Global CMT Convention Moment Tensor:
R T P
-3.40e+13 3.39e+19 3.88e+20
3.39e+19 -7.73e+20 -4.38e+21
3.88e+20 -4.38e+21 7.73e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20120627011420/index.html
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STK = 5
DIP = 90
RAKE = 5
MW = 3.70
HS = 5.0
The waveform inversion is preferred.
The following compares this source inversion to others
SLU Moment Tensor Solution
ENS 2012/06/27 01:14:20:0 37.00 15.03 3.0 3.7 Italy
Stations used:
IV.ECNV IV.GALF IV.HAGA IV.HCRL IV.HLNI IV.HMDC IV.RESU
IV.SSY
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 4.47e+21 dyne-cm
Mw = 3.70
Z = 5 km
Plane Strike Dip Rake
NP1 5 90 5
NP2 275 85 180
Principal Axes:
Axis Value Plunge Azimuth
T 4.47e+21 4 230
N 0.00e+00 85 5
P -4.47e+21 4 140
Moment Tensor: (dyne-cm)
Component Value
Mxx -7.73e+20
Mxy 4.38e+21
Mxz 3.39e+19
Myy 7.73e+20
Myz -3.88e+20
Mzz -3.40e+13
---------#####
-------------#########
---------------#############
----------------##############
------------------################
-------------------#################
--------------------##################
---------------------###################
--------------------####################
---------------------#####################
#####################----#################
#####################-----------------####
#####################---------------------
####################--------------------
###################---------------------
##################--------------------
#################-------------------
# ############------------------
T ############------------ -
############------------ P
#########-------------
#####---------
Global CMT Convention Moment Tensor:
R T P
-3.40e+13 3.39e+19 3.88e+20
3.39e+19 -7.73e+20 -4.38e+21
3.88e+20 -4.38e+21 7.73e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20120627011420/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 5 90 5 3.48 0.3964
WVFGRD96 2.0 5 90 5 3.56 0.4533
WVFGRD96 3.0 5 90 10 3.61 0.4859
WVFGRD96 4.0 185 90 -5 3.66 0.5080
WVFGRD96 5.0 5 90 5 3.70 0.5193
WVFGRD96 6.0 185 90 -5 3.73 0.5185
WVFGRD96 7.0 185 90 -10 3.75 0.5137
WVFGRD96 8.0 5 90 5 3.76 0.5079
WVFGRD96 9.0 5 90 5 3.78 0.5035
WVFGRD96 10.0 5 90 5 3.79 0.4992
WVFGRD96 11.0 5 90 5 3.80 0.4961
WVFGRD96 12.0 185 85 -10 3.81 0.4945
WVFGRD96 13.0 185 85 -10 3.83 0.4922
WVFGRD96 14.0 185 90 -5 3.84 0.4889
WVFGRD96 15.0 185 85 -10 3.85 0.4868
WVFGRD96 16.0 185 85 -10 3.86 0.4865
WVFGRD96 17.0 185 85 -10 3.87 0.4845
WVFGRD96 18.0 185 85 -10 3.88 0.4828
WVFGRD96 19.0 5 90 10 3.89 0.4850
WVFGRD96 20.0 5 90 10 3.90 0.4857
WVFGRD96 21.0 5 90 10 3.91 0.4921
WVFGRD96 22.0 185 90 -15 3.91 0.4928
WVFGRD96 23.0 185 90 -15 3.92 0.4993
WVFGRD96 24.0 185 90 -15 3.93 0.4997
WVFGRD96 25.0 5 90 20 3.93 0.5032
WVFGRD96 26.0 185 90 -20 3.94 0.5017
WVFGRD96 27.0 5 90 20 3.96 0.5001
WVFGRD96 28.0 5 90 20 3.97 0.4966
WVFGRD96 29.0 185 90 -20 3.98 0.4919
The best solution is
WVFGRD96 5.0 5 90 5 3.70 0.5193
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. A pair of numbers is given in black at the right of each predicted traces. The upper number 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 lower number gives the percentage of variance reduction to characterize the individual goodness of fit (100% indicates a perfect fit).
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. |
A check on the assumed source location is possible by looking at the time shifts between the observed and predicted traces. The time shifts for waveform matching arise for several reasons:
Time_shift = A + B cos Azimuth + C Sin Azimuth
The time shifts for this inversion lead to the next figure:
The derived shift in origin time and epicentral coordinates are given at the bottom of 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 Jun 27 00:33:04 CDT 2012