2009/04/06 23:49:34 42.349 13.378 8.3 3.00 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/06 23:49:34:0 42.35 13.38 8.3 3.0 Italy
Stations used:
IV.ASSB IV.CAFR IV.FAGN IV.FDMO IV.FIAM IV.INTR IV.MIDA
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 = 7.94e+20 dyne-cm
Mw = 3.20
Z = 5 km
Plane Strike Dip Rake
NP1 155 50 -60
NP2 293 48 -121
Principal Axes:
Axis Value Plunge Azimuth
T 7.94e+20 1 224
N 0.00e+00 23 315
P -7.94e+20 67 132
Moment Tensor: (dyne-cm)
Component Value
Mxx 3.54e+20
Mxy 4.55e+20
Mxz 1.81e+20
Myy 3.23e+20
Myz -2.16e+20
Mzz -6.77e+20
##############
-#####################
----########################
----##########################
-----#############################
--####---------------###############
#######-------------------############
########----------------------##########
########------------------------########
##########-------------------------#######
##########--------------------------######
###########---------------------------####
###########------------- ------------###
###########------------ P ------------##
############----------- -------------#
############--------------------------
#############-----------------------
#############---------------------
##########-----------------
T ############--------------
###############-------
##############
Global CMT Convention Moment Tensor:
R T P
-6.77e+20 1.81e+20 2.16e+20
1.81e+20 3.54e+20 -4.55e+20
2.16e+20 -4.55e+20 3.23e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090406234934/index.html
|
STK = 155
DIP = 50
RAKE = -60
MW = 3.20
HS = 5.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/06 23:49:34:0 42.35 13.38 8.3 3.0 Italy
Stations used:
IV.ASSB IV.CAFR IV.FAGN IV.FDMO IV.FIAM IV.INTR IV.MIDA
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 = 7.94e+20 dyne-cm
Mw = 3.20
Z = 5 km
Plane Strike Dip Rake
NP1 155 50 -60
NP2 293 48 -121
Principal Axes:
Axis Value Plunge Azimuth
T 7.94e+20 1 224
N 0.00e+00 23 315
P -7.94e+20 67 132
Moment Tensor: (dyne-cm)
Component Value
Mxx 3.54e+20
Mxy 4.55e+20
Mxz 1.81e+20
Myy 3.23e+20
Myz -2.16e+20
Mzz -6.77e+20
##############
-#####################
----########################
----##########################
-----#############################
--####---------------###############
#######-------------------############
########----------------------##########
########------------------------########
##########-------------------------#######
##########--------------------------######
###########---------------------------####
###########------------- ------------###
###########------------ P ------------##
############----------- -------------#
############--------------------------
#############-----------------------
#############---------------------
##########-----------------
T ############--------------
###############-------
##############
Global CMT Convention Moment Tensor:
R T P
-6.77e+20 1.81e+20 2.16e+20
1.81e+20 3.54e+20 -4.55e+20
2.16e+20 -4.55e+20 3.23e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090406234934/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.
|
|
|
|
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 0.5 150 55 -70 2.96 0.3219
WVFGRD96 1.0 165 60 -55 2.99 0.3441
WVFGRD96 2.0 165 60 -55 3.07 0.4081
WVFGRD96 3.0 165 55 -50 3.09 0.4471
WVFGRD96 4.0 165 55 -50 3.11 0.4516
WVFGRD96 5.0 155 50 -60 3.20 0.4707
WVFGRD96 6.0 165 55 -50 3.17 0.4351
WVFGRD96 7.0 175 65 -35 3.15 0.4062
WVFGRD96 8.0 180 75 -25 3.14 0.3873
WVFGRD96 9.0 180 75 -25 3.15 0.3826
WVFGRD96 10.0 180 75 -25 3.16 0.3753
WVFGRD96 11.0 180 75 -25 3.17 0.3676
WVFGRD96 12.0 180 70 -25 3.18 0.3601
WVFGRD96 13.0 135 80 35 3.25 0.3648
WVFGRD96 14.0 135 80 40 3.25 0.3696
WVFGRD96 15.0 135 80 40 3.29 0.3731
WVFGRD96 16.0 135 80 40 3.30 0.3770
WVFGRD96 17.0 310 90 -40 3.32 0.3721
WVFGRD96 18.0 135 80 40 3.32 0.3779
WVFGRD96 19.0 310 90 -40 3.34 0.3746
WVFGRD96 20.0 130 90 40 3.35 0.3736
WVFGRD96 21.0 130 90 40 3.36 0.3699
WVFGRD96 22.0 310 90 -40 3.37 0.3668
WVFGRD96 23.0 130 85 40 3.37 0.3663
WVFGRD96 24.0 310 90 -35 3.39 0.3662
WVFGRD96 25.0 310 90 -35 3.40 0.3683
WVFGRD96 26.0 310 90 -35 3.41 0.3699
WVFGRD96 27.0 310 90 -35 3.42 0.3688
WVFGRD96 28.0 135 80 35 3.41 0.3710
WVFGRD96 29.0 135 85 30 3.44 0.3692
The best solution is
WVFGRD96 5.0 155 50 -60 3.20 0.4707
The mechanism correspond to the best fit is
|
|
|
The best fit as a function of depth is given in the following figure:
|
|
|
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
|
|
|
|
| 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=Fri May 1 15:00:49 CDT 2009