Location
2013/08/22 06:44:50 43.583 13.804 7.9 4.4 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 2013/08/22 06:44:50:0 43.58 13.80 7.9 4.4 Italy
Stations used:
IV.ARVD IV.ASQU IV.CAFI IV.CERT IV.CESI IV.CESX IV.CING
IV.FDMO IV.FIAM IV.FSSB IV.GUMA IV.LNSS IV.MGAB IV.MTCE
IV.NRCA IV.PARC IV.PESA IV.PTQR IV.SACS IV.SNTG IV.SSFR
IV.T0104 IV.TERO IV.VVLD
Filtering commands used:
cut a -10 a 80
rtr
taper w 0.1
hp c 0.02 n 3
lp c 0.05 n 3
Best Fitting Double Couple
Mo = 2.51e+22 dyne-cm
Mw = 4.20
Z = 5 km
Plane Strike Dip Rake
NP1 310 50 80
NP2 145 41 102
Principal Axes:
Axis Value Plunge Azimuth
T 2.51e+22 81 167
N 0.00e+00 8 316
P -2.51e+22 5 47
Moment Tensor: (dyne-cm)
Component Value
Mxx -1.10e+22
Mxy -1.26e+22
Mxz -5.09e+21
Myy -1.34e+22
Myz -6.13e+20
Mzz 2.44e+22
--------------
----------------------
#--------------------------
#-#######------------------- P
---##############------------- -
----#################---------------
----#####################-------------
-----#######################------------
------########################----------
-------#########################----------
-------##########################---------
--------############ ############-------
---------########### T ############-------
---------########## #############-----
----------##########################----
----------#########################---
-----------#######################--
------------#####################-
------------##################
---------------#############
----------------------
--------------
Global CMT Convention Moment Tensor:
R T P
2.44e+22 -5.09e+21 6.13e+20
-5.09e+21 -1.10e+22 1.26e+22
6.13e+20 1.26e+22 -1.34e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20130822064450/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 = 310
DIP = 50
RAKE = 80
MW = 4.20
HS = 5.0
The NDK file is 20130822064450.ndk
The waveform inversion is preferred.
Moment Tensor Comparison
The following compares this source inversion to others
| SLU |
INGVTDMT |
SLU Moment Tensor Solution
ENS 2013/08/22 06:44:50:0 43.58 13.80 7.9 4.4 Italy
Stations used:
IV.ARVD IV.ASQU IV.CAFI IV.CERT IV.CESI IV.CESX IV.CING
IV.FDMO IV.FIAM IV.FSSB IV.GUMA IV.LNSS IV.MGAB IV.MTCE
IV.NRCA IV.PARC IV.PESA IV.PTQR IV.SACS IV.SNTG IV.SSFR
IV.T0104 IV.TERO IV.VVLD
Filtering commands used:
cut a -10 a 80
rtr
taper w 0.1
hp c 0.02 n 3
lp c 0.05 n 3
Best Fitting Double Couple
Mo = 2.51e+22 dyne-cm
Mw = 4.20
Z = 5 km
Plane Strike Dip Rake
NP1 310 50 80
NP2 145 41 102
Principal Axes:
Axis Value Plunge Azimuth
T 2.51e+22 81 167
N 0.00e+00 8 316
P -2.51e+22 5 47
Moment Tensor: (dyne-cm)
Component Value
Mxx -1.10e+22
Mxy -1.26e+22
Mxz -5.09e+21
Myy -1.34e+22
Myz -6.13e+20
Mzz 2.44e+22
--------------
----------------------
#--------------------------
#-#######------------------- P
---##############------------- -
----#################---------------
----#####################-------------
-----#######################------------
------########################----------
-------#########################----------
-------##########################---------
--------############ ############-------
---------########### T ############-------
---------########## #############-----
----------##########################----
----------#########################---
-----------#######################--
------------#####################-
------------##################
---------------#############
----------------------
--------------
Global CMT Convention Moment Tensor:
R T P
2.44e+22 -5.09e+21 6.13e+20
-5.09e+21 -1.10e+22 1.26e+22
6.13e+20 1.26e+22 -1.34e+22
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20130822064450/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.
|
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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:
cut a -10 a 80
rtr
taper w 0.1
hp c 0.02 n 3
lp c 0.05 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 1.0 295 55 55 3.97 0.4449
WVFGRD96 2.0 300 55 65 4.04 0.5102
WVFGRD96 3.0 310 50 80 4.11 0.5683
WVFGRD96 4.0 315 45 85 4.16 0.5942
WVFGRD96 5.0 310 50 80 4.20 0.6223
WVFGRD96 6.0 305 50 75 4.20 0.5534
WVFGRD96 7.0 290 60 50 4.15 0.4629
WVFGRD96 8.0 85 60 -5 4.08 0.4286
WVFGRD96 9.0 85 60 -10 4.09 0.4287
WVFGRD96 10.0 270 70 -35 4.12 0.4367
WVFGRD96 11.0 270 70 -35 4.13 0.4454
WVFGRD96 12.0 270 70 -35 4.13 0.4525
WVFGRD96 13.0 270 70 -30 4.14 0.4589
WVFGRD96 14.0 270 70 -30 4.15 0.4646
WVFGRD96 15.0 270 75 -40 4.18 0.4650
WVFGRD96 16.0 270 75 -40 4.19 0.4694
WVFGRD96 17.0 270 75 -40 4.20 0.4726
WVFGRD96 18.0 270 75 -35 4.21 0.4750
WVFGRD96 19.0 270 75 -35 4.22 0.4768
WVFGRD96 20.0 270 75 -35 4.23 0.4779
WVFGRD96 21.0 270 75 -35 4.23 0.4784
WVFGRD96 22.0 270 75 -35 4.24 0.4782
WVFGRD96 23.0 270 75 -35 4.25 0.4776
WVFGRD96 24.0 270 75 -35 4.26 0.4764
WVFGRD96 25.0 275 80 -35 4.27 0.4752
WVFGRD96 26.0 270 75 -35 4.28 0.4760
WVFGRD96 27.0 270 75 -35 4.29 0.4780
WVFGRD96 28.0 270 75 -35 4.30 0.4795
WVFGRD96 29.0 270 75 -30 4.31 0.4821
The best solution is
WVFGRD96 5.0 310 50 80 4.20 0.6223
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:
|
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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
cut a -10 a 80
rtr
taper w 0.1
hp c 0.02 n 3
lp c 0.05 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=Thu Aug 22 06:10:29 CDT 2013
Last Changed 2013/08/22
