aftershock sequences in the little carpatian region following two earthquakes in 2006
DESCRIPTION
AIM Third A nnual M eeting October, 10 .- 12 ., 201 2 Smolenice. Aftershock sequences in the Little Carpatian region following two earthquakes in 2006. Ji ří Málek and Lucia Fojtíková Institute of Rock Structure and Mechanics, v.v.i. Juraj Seker eš - PowerPoint PPT PresentationTRANSCRIPT
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Aftershock sequences
in the Little Carpatian region
following two earthquakes in 2006
AIM Third Annual Meeting
October, 10.-12., 2012 Smolenice
Jiří Málek and Lucia Fojtíková
Institute of Rock Structure and Mechanics, v.v.i.
Juraj Sekereš
Progseis, Ltd., Trnava, Slovakia
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Motivation
Seismic activity 1987-2010
source.: Progseis, Ltd, GPI SAS, EQUIS, Ltd.
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Tectonic situation
2006, Ml=2.2
2006, Ml=3.4
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Focal mechanism
ID
Date
Time
Mw
Latitude
Longitude
Depth
Focal mechanism
V03
13.3.2006 08:28:38.39
3.4
48.550
17.694
10.2
V14
5.8.2006 09:00:08.63
2.2
48,516
17,468
5.2
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Aftershocks
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New Stations
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Method
Master-event relative location
• The shape of an aftershock cluster is determined.
• Time differences between aftershock and the main shock (master event) are used.
• The seismograms are compared only at the same station (not between stations).
• Similarity of the seismograms enables to read time differences more accurately.
• Relative locations are less sensitive to the velocity model.
• Linear inverse problem, which can be easily solved.
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Method
earthquakejstationiP
jiS
konstv
vk
s
p 1jiu
jx
jir
Mi
ji
ji rrr
ji
Mi
jip
ji xuDDkvr
)(
jmi
Mm
jm
Mi
jip
jm
ji xuuPPPPvrr
)(
Index M means master-event (normaly the main shock) Index m means master-station (normaly the nearest station)
unit vector of the ray leaving j-th event to i-th station
space vector from master-event to j-th event - unknown
travel distance of j-th event and i-th station
ji
ji
ji PSD
iMi
ji uuu
Linear inverse problem
Velocity model
Data
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Application at WEBNET
46000 47000 48000 49000
7000
8000
9000
10000
dR
Master event
15000 20000 25000 30000 35000 40000 45000Y (m )
40000
45000
50000
55000
60000
65000
70000
X (
m)
NKC
KOC
KRC
SKC
STC
VAC
LBC
SNE
KVE
Z(m)
X(m)
Málek and Horálek, 2008
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Master-event
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Master-event
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Master-event
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Master-event
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Master-event
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Master-event
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Master-event
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Data
SMOL
SMOL
KATA
KATA
P
S
Z Z
N E
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Result and Model sensitivity
-2 -1 0 1 2
X (km) East
-2
-1
0
1
2
Y (
km)
Nor
th
Grad. model vp=5.5 km/s Hom. model vp=6.0 km/s
Grad. model vp=6.0 km/s
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Result and Model sensitivity
-2 -1 0 1 2
X (km) East
-2
-1
0
1
2
Z (
km)
Up
Grad. model vp=5.5 km/s Hom. model vp=6.0 km/s Grad. model vp=6.0 km/s
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Results
Dep
th
Y
X
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Conclusions
J. Hók, modified after Fusán et. al 1987
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Conclusions
J. Hók, modified after Fusán et. al 1987
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Conclusions
• Master-event method is a useful tool for determination of aftershock cluster shape
• It can be applied even to small magnitudes (ML=2.2)
• One of the nodal plane was selected as fault plane, with azimuth of about 300°
• This fault was identified on tectonic map
• Faults of NW-SE azimuths are active in the Little Carpathian region
and they are important for seismic hazard assesment