Location
2013/03/18 02:40:50 43.142 11.434 9.6 3.6 Italy
Arrival Times (from USGS)
Arrival time list
Felt Map
USGS Felt map for this earthquake
USGS Felt reports page for
Focal Mechanism
SLU Moment Tensor Solution
ENS 2013/03/18 02:40:50:0 43.14 11.43 9.6 3.6 Italy
Stations used:
GU.MAIM GU.POPM IV.AOI IV.ARVD IV.ASQU IV.ASSB IV.BDI
IV.CAFI IV.CAMP IV.CASP IV.CESI IV.CESX IV.CING IV.CRMI
IV.CSNT IV.FDMO IV.FNVD IV.FSSB IV.GUMA IV.LNSS IV.MAON
IV.MGAB IV.MTCE IV.MTRZ IV.MURB IV.NRCA IV.OFFI IV.PARC
IV.PESA IV.PIEI IV.SACS IV.SNTG IV.SSFR IV.TERO IV.ZCCA
MN.AQU MN.VLC
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 3.76e+21 dyne-cm
Mw = 3.65
Z = 7 km
Plane Strike Dip Rake
NP1 340 80 -40
NP2 78 51 -167
Principal Axes:
Axis Value Plunge Azimuth
T 3.76e+21 19 35
N 0.00e+00 49 148
P -3.76e+21 35 291
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.92e+21
Mxy 2.44e+21
Mxz 3.07e+20
Myy -1.09e+21
Myz 2.30e+21
Mzz -8.26e+20
##############
-----#################
----------############ ###
------------########### T ####
---------------########## ######
-----------------###################
------------------####################
------ -----------####################
------ P ------------###################
------- -------------##################-
-----------------------#################--
------------------------##############----
-------------------------############-----
------------------------#########-------
##-----------------------######---------
#####-------------------##------------
###########------#######------------
#######################-----------
######################--------
#####################-------
##################----
##############
Global CMT Convention Moment Tensor:
R T P
-8.26e+20 3.07e+20 -2.30e+21
3.07e+20 1.92e+21 -2.44e+21
-2.30e+21 -2.44e+21 -1.09e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20130318024050/index.html
|
Preferred Solution
The preferred solution from an analysis of the surface-wave spectral amplitude radiation pattern, waveform inversion and first motion observations is
STK = 340
DIP = 80
RAKE = -40
MW = 3.65
HS = 7.0
The waveform inversion is preferred.
Moment Tensor Comparison
The following compares this source inversion to others
| SLU |
INGVTDMT |
SLU Moment Tensor Solution
ENS 2013/03/18 02:40:50:0 43.14 11.43 9.6 3.6 Italy
Stations used:
GU.MAIM GU.POPM IV.AOI IV.ARVD IV.ASQU IV.ASSB IV.BDI
IV.CAFI IV.CAMP IV.CASP IV.CESI IV.CESX IV.CING IV.CRMI
IV.CSNT IV.FDMO IV.FNVD IV.FSSB IV.GUMA IV.LNSS IV.MAON
IV.MGAB IV.MTCE IV.MTRZ IV.MURB IV.NRCA IV.OFFI IV.PARC
IV.PESA IV.PIEI IV.SACS IV.SNTG IV.SSFR IV.TERO IV.ZCCA
MN.AQU MN.VLC
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 3.76e+21 dyne-cm
Mw = 3.65
Z = 7 km
Plane Strike Dip Rake
NP1 340 80 -40
NP2 78 51 -167
Principal Axes:
Axis Value Plunge Azimuth
T 3.76e+21 19 35
N 0.00e+00 49 148
P -3.76e+21 35 291
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.92e+21
Mxy 2.44e+21
Mxz 3.07e+20
Myy -1.09e+21
Myz 2.30e+21
Mzz -8.26e+20
##############
-----#################
----------############ ###
------------########### T ####
---------------########## ######
-----------------###################
------------------####################
------ -----------####################
------ P ------------###################
------- -------------##################-
-----------------------#################--
------------------------##############----
-------------------------############-----
------------------------#########-------
##-----------------------######---------
#####-------------------##------------
###########------#######------------
#######################-----------
######################--------
#####################-------
##################----
##############
Global CMT Convention Moment Tensor:
R T P
-8.26e+20 3.07e+20 -2.30e+21
3.07e+20 1.92e+21 -2.44e+21
-2.30e+21 -2.44e+21 -1.09e+21
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20130318024050/index.html
|
|
Waveform Inversion
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.
|
|
Location of broadband stations used for waveform inversion
|
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 3
The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT
WVFGRD96 1.0 160 60 -45 3.45 0.3775
WVFGRD96 2.0 170 90 55 3.54 0.4125
WVFGRD96 3.0 340 80 -50 3.54 0.4770
WVFGRD96 4.0 345 85 -40 3.55 0.5205
WVFGRD96 5.0 335 75 -50 3.63 0.5568
WVFGRD96 6.0 340 80 -45 3.64 0.5731
WVFGRD96 7.0 340 80 -40 3.65 0.5791
WVFGRD96 8.0 345 85 -30 3.64 0.5739
WVFGRD96 9.0 345 85 -30 3.65 0.5654
WVFGRD96 10.0 345 85 -30 3.66 0.5514
WVFGRD96 11.0 345 85 -30 3.67 0.5332
WVFGRD96 12.0 345 85 -25 3.69 0.5130
WVFGRD96 13.0 345 85 -25 3.70 0.4901
WVFGRD96 14.0 345 85 -25 3.71 0.4648
WVFGRD96 15.0 345 85 -30 3.72 0.4391
WVFGRD96 16.0 340 85 -30 3.72 0.4140
WVFGRD96 17.0 340 85 -35 3.72 0.3892
WVFGRD96 18.0 165 85 35 3.73 0.3659
WVFGRD96 19.0 340 85 -35 3.73 0.3442
WVFGRD96 20.0 165 85 35 3.74 0.3258
WVFGRD96 21.0 160 90 35 3.74 0.3106
WVFGRD96 22.0 160 90 35 3.75 0.2989
WVFGRD96 23.0 160 90 35 3.76 0.2899
WVFGRD96 24.0 340 85 -35 3.77 0.2848
WVFGRD96 25.0 340 85 -30 3.78 0.2799
WVFGRD96 26.0 340 85 -30 3.79 0.2764
WVFGRD96 27.0 345 85 -30 3.81 0.2738
WVFGRD96 28.0 345 85 -25 3.82 0.2724
WVFGRD96 29.0 170 85 20 3.85 0.2714
The best solution is
WVFGRD96 7.0 340 80 -40 3.65 0.5791
The mechanism correspond to the best fit is
|
|
Figure 1. Waveform inversion focal mechanism
|
The best fit as a function of depth is given in the following figure:
|
|
Figure 2. Depth sensitivity for waveform mechanism
|
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
|
|
Figure 3. Waveform comparison for selected depth
|
|
|
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:
- The origin time and epicentral distance are incorrect
- The velocity model used for the inversion is incorrect
- The velocity model used to define the P-arrival time is not the
same as the velocity model used for the waveform inversion
(assuming that the initial trace alignment is based on the
P arrival time)
Assuming only a mislocation, the time shifts are fit to a functional form:
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.
Discussion
Velocity Model
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
Quality Control
Here we tabulate the reasons for not using certain digital data sets
The following stations did not have a valid response files:
DATE=Mon Mar 18 21:59:54 CDT 2013
Last Changed 2013/03/18
