Location
2013/06/21 12:19:58 44.168 10.120 4.4 3.8 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 2013/06/21 12:19:58:0 44.17 10.12 4.4 3.8 Italy
Stations used:
GU.BHB GU.ENR GU.FINB GU.GORR GU.MAIM GU.PCP IV.ARVD
IV.ASQU IV.BDI IV.BOB IV.CAFI IV.CASP IV.CRMI IV.CSNT
IV.DOI IV.FNVD IV.FSSB IV.IMI IV.MGAB IV.MSSA IV.MURB
IV.PARC IV.PIEI IV.QLNO IV.SACS IV.SSFR MN.VLC
Filtering commands used:
cut a -30 a 90
rtr
taper w 0.1
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 4.17e+21 dyne-cm
Mw = 3.68
Z = 7 km
Plane Strike Dip Rake
NP1 295 50 -75
NP2 92 42 -107
Principal Axes:
Axis Value Plunge Azimuth
T 4.17e+21 4 14
N 0.00e+00 11 105
P -4.17e+21 78 266
Moment Tensor: (dyne-cm)
Component Value
Mxx 3.89e+21
Mxy 9.88e+20
Mxz 3.41e+20
Myy 7.51e+19
Myz 9.24e+20
Mzz -3.97e+21
########## T #
############## #####
############################
##############################
##################################
##------------------################
-------------------------#############
-----------------------------###########
-------------------------------#########
----------------------------------########
---------------- -----------------######
#--------------- P ------------------#####
##-------------- -------------------###-
###-------------------------------------
#####-------------------------------##--
######---------------------------#####
#########-------------------########
##################################
##############################
############################
######################
##############
Global CMT Convention Moment Tensor:
R T P
-3.97e+21 3.41e+20 -9.24e+20
3.41e+20 3.89e+21 -9.88e+20
-9.24e+20 -9.88e+20 7.51e+19
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20130621121958/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 = 295
DIP = 50
RAKE = -75
MW = 3.68
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 2013/06/21 12:19:58:0 44.17 10.12 4.4 3.8 Italy
Stations used:
GU.BHB GU.ENR GU.FINB GU.GORR GU.MAIM GU.PCP IV.ARVD
IV.ASQU IV.BDI IV.BOB IV.CAFI IV.CASP IV.CRMI IV.CSNT
IV.DOI IV.FNVD IV.FSSB IV.IMI IV.MGAB IV.MSSA IV.MURB
IV.PARC IV.PIEI IV.QLNO IV.SACS IV.SSFR MN.VLC
Filtering commands used:
cut a -30 a 90
rtr
taper w 0.1
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 4.17e+21 dyne-cm
Mw = 3.68
Z = 7 km
Plane Strike Dip Rake
NP1 295 50 -75
NP2 92 42 -107
Principal Axes:
Axis Value Plunge Azimuth
T 4.17e+21 4 14
N 0.00e+00 11 105
P -4.17e+21 78 266
Moment Tensor: (dyne-cm)
Component Value
Mxx 3.89e+21
Mxy 9.88e+20
Mxz 3.41e+20
Myy 7.51e+19
Myz 9.24e+20
Mzz -3.97e+21
########## T #
############## #####
############################
##############################
##################################
##------------------################
-------------------------#############
-----------------------------###########
-------------------------------#########
----------------------------------########
---------------- -----------------######
#--------------- P ------------------#####
##-------------- -------------------###-
###-------------------------------------
#####-------------------------------##--
######---------------------------#####
#########-------------------########
##################################
##############################
############################
######################
##############
Global CMT Convention Moment Tensor:
R T P
-3.97e+21 3.41e+20 -9.24e+20
3.41e+20 3.89e+21 -9.88e+20
-9.24e+20 -9.88e+20 7.51e+19
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20130621121958/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
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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:
cut a -30 a 90
rtr
taper w 0.1
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 70 35 3.30 0.3426
WVFGRD96 2.0 335 85 -65 3.51 0.3960
WVFGRD96 3.0 325 70 -55 3.51 0.4799
WVFGRD96 4.0 315 60 -60 3.54 0.5356
WVFGRD96 5.0 310 45 -45 3.60 0.5497
WVFGRD96 6.0 300 45 -65 3.66 0.5829
WVFGRD96 7.0 295 50 -75 3.68 0.5882
WVFGRD96 8.0 295 50 -70 3.62 0.5696
WVFGRD96 9.0 295 50 -70 3.62 0.5439
WVFGRD96 10.0 295 55 -70 3.62 0.5167
WVFGRD96 11.0 295 60 -65 3.61 0.4925
WVFGRD96 12.0 295 65 -65 3.62 0.4702
WVFGRD96 13.0 320 55 -10 3.54 0.4469
WVFGRD96 14.0 325 55 10 3.55 0.4356
WVFGRD96 15.0 325 55 10 3.58 0.4241
WVFGRD96 16.0 325 55 10 3.59 0.4121
WVFGRD96 17.0 325 55 10 3.60 0.3993
WVFGRD96 18.0 320 55 5 3.60 0.3865
WVFGRD96 19.0 320 55 5 3.61 0.3739
WVFGRD96 20.0 320 55 5 3.61 0.3611
WVFGRD96 21.0 320 55 5 3.62 0.3481
WVFGRD96 22.0 320 55 5 3.63 0.3360
WVFGRD96 23.0 320 55 5 3.64 0.3252
WVFGRD96 24.0 320 55 10 3.64 0.3159
WVFGRD96 25.0 320 60 5 3.66 0.3076
WVFGRD96 26.0 320 60 5 3.67 0.3012
WVFGRD96 27.0 320 60 10 3.68 0.2965
WVFGRD96 28.0 320 60 10 3.69 0.2918
WVFGRD96 29.0 165 75 25 3.76 0.2933
The best solution is
WVFGRD96 7.0 295 50 -75 3.68 0.5882
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 -30 a 90
rtr
taper w 0.1
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=Fri Jun 21 14:23:02 CDT 2013
Last Changed 2013/06/21
