2009/04/07 21:34:29 42.380 13.376 10.0 4.20 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/07 21:34:29:0 42.38 13.38 10.0 4.2 Italy
Stations used:
IV.ASSB IV.CAMP IV.CESI IV.CING IV.FDMO IV.FIAM IV.INTR
IV.LNSS IV.MNS IV.OFFI IV.TERO
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 2.04e+22 dyne-cm
Mw = 4.14
Z = 5 km
Plane Strike Dip Rake
NP1 165 60 -40
NP2 278 56 -143
Principal Axes:
Axis Value Plunge Azimuth
T 2.04e+22 2 222
N 0.00e+00 42 314
P -2.04e+22 48 130
Moment Tensor: (dyne-cm)
Component Value
Mxx 7.53e+21
Mxy 1.46e+22
Mxz 5.86e+21
Myy 3.83e+21
Myz -8.36e+21
Mzz -1.14e+22
-#############
----##################
-------#####################
-------#######################
---------#########################
---------###########################
---------------------#################
-----######------------------###########
--#########----------------------#######
#############------------------------#####
#############--------------------------###
#############---------------------------##
##############----------------------------
#############-------------- ----------
##############------------- P ----------
##############------------ ---------
##############----------------------
##############--------------------
##########-----------------
T ############--------------
#############---------
###########---
Global CMT Convention Moment Tensor:
R T P
-1.14e+22 5.86e+21 8.36e+21
5.86e+21 7.53e+21 -1.46e+22
8.36e+21 -1.46e+22 3.83e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090407213429/index.html
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STK = 165
DIP = 60
RAKE = -40
MW = 4.14
HS = 5.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/07 21:34:29:0 42.38 13.38 10.0 4.2 Italy
Stations used:
IV.ASSB IV.CAMP IV.CESI IV.CING IV.FDMO IV.FIAM IV.INTR
IV.LNSS IV.MNS IV.OFFI IV.TERO
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 2.04e+22 dyne-cm
Mw = 4.14
Z = 5 km
Plane Strike Dip Rake
NP1 165 60 -40
NP2 278 56 -143
Principal Axes:
Axis Value Plunge Azimuth
T 2.04e+22 2 222
N 0.00e+00 42 314
P -2.04e+22 48 130
Moment Tensor: (dyne-cm)
Component Value
Mxx 7.53e+21
Mxy 1.46e+22
Mxz 5.86e+21
Myy 3.83e+21
Myz -8.36e+21
Mzz -1.14e+22
-#############
----##################
-------#####################
-------#######################
---------#########################
---------###########################
---------------------#################
-----######------------------###########
--#########----------------------#######
#############------------------------#####
#############--------------------------###
#############---------------------------##
##############----------------------------
#############-------------- ----------
##############------------- P ----------
##############------------ ---------
##############----------------------
##############--------------------
##########-----------------
T ############--------------
#############---------
###########---
Global CMT Convention Moment Tensor:
R T P
-1.14e+22 5.86e+21 8.36e+21
5.86e+21 7.53e+21 -1.46e+22
8.36e+21 -1.46e+22 3.83e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090407213429/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 0.5 125 45 85 3.86 0.2716
WVFGRD96 1.0 90 80 5 3.79 0.2551
WVFGRD96 2.0 330 55 -60 4.02 0.3232
WVFGRD96 3.0 325 50 -70 4.12 0.4252
WVFGRD96 4.0 330 50 -60 4.14 0.4609
WVFGRD96 5.0 165 60 -40 4.14 0.4730
WVFGRD96 6.0 165 60 -35 4.16 0.4710
WVFGRD96 7.0 170 70 -25 4.17 0.4643
WVFGRD96 8.0 165 60 -35 4.23 0.4672
WVFGRD96 9.0 170 70 -25 4.24 0.4521
WVFGRD96 10.0 180 70 15 4.25 0.4445
WVFGRD96 11.0 180 70 20 4.27 0.4437
WVFGRD96 12.0 180 70 20 4.28 0.4410
WVFGRD96 13.0 350 75 -30 4.30 0.4428
WVFGRD96 14.0 350 75 -30 4.32 0.4412
WVFGRD96 15.0 350 75 -30 4.33 0.4373
WVFGRD96 16.0 355 80 -25 4.34 0.4338
WVFGRD96 17.0 355 80 -25 4.36 0.4307
WVFGRD96 18.0 355 80 -25 4.37 0.4266
WVFGRD96 19.0 180 80 20 4.37 0.4187
WVFGRD96 20.0 185 60 35 4.37 0.4168
WVFGRD96 21.0 185 60 30 4.39 0.4175
WVFGRD96 22.0 185 60 30 4.40 0.4193
WVFGRD96 23.0 185 60 30 4.41 0.4198
WVFGRD96 24.0 185 60 30 4.41 0.4197
WVFGRD96 25.0 185 60 30 4.42 0.4182
WVFGRD96 26.0 185 60 30 4.43 0.4152
WVFGRD96 27.0 185 60 30 4.44 0.4128
WVFGRD96 28.0 185 60 30 4.44 0.4081
WVFGRD96 29.0 185 60 30 4.45 0.4037
The best solution is
WVFGRD96 5.0 165 60 -40 4.14 0.4730
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 WUS used for the waveform synthetic seismograms and for the surface wave eigenfunctions and dispersion is as follows:
MODEL.01
Model after 8 iterations
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
1.9000 3.4065 2.0089 2.2150 0.302E-02 0.679E-02 0.00 0.00 1.00 1.00
6.1000 5.5445 3.2953 2.6089 0.349E-02 0.784E-02 0.00 0.00 1.00 1.00
13.0000 6.2708 3.7396 2.7812 0.212E-02 0.476E-02 0.00 0.00 1.00 1.00
19.0000 6.4075 3.7680 2.8223 0.111E-02 0.249E-02 0.00 0.00 1.00 1.00
0.0000 7.9000 4.6200 3.2760 0.164E-10 0.370E-10 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=Thu Apr 16 09:40:07 CDT 2009