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MICRO-SEISMICITY AND FOCAL MECHANISMS
IN THE MALÉ KARPATY MTS.,
SLOVAKIA
Lucia Fojtíková, Václav Vavryčuk, Andrej Cipciar, Ján Madarás
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Seismic Activity in the Malé Karpaty Mts.
• January 9th 1906 – the strongest earthquakes in the region in 20th century• Ms = 5.7; h=15 km, epicentral intensity Io = 8° MSK-64
Period: 1034 - 2006
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Seismic Stations
Seismic stations in SlovakiaNational seismic networkLocal seismic network LSSVSLocal seismic network EBOLocal seismic network EMO
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Geological Map
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Tectonic Sketch
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P-wave Velocity Model
JABO
BUKO KATA
LANC
PLAV
MODS
SPAC
SMOL
KATA
HOST
DVODLAKS
[km/s]
N
[km]
JABO
BUKO KATA
LANC
PLAV
MODS
SPAC
SMOL
KATA
HOST
DVODLAKS
[km/s]
NN
[km]
4.0 5.0 6.0 7.0P-w ave ve locity [km /s]
30
20
10
0
De
pth
[km
]
3D 1D
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Data
• 44 micro-earthquakes
• Period 2001 - 2009
• Area: 30km x 60km
• Magnitudes of events analyzed: 1.1 – 3.2
• Hypocenter depths: 1km – 15km
• Seismometers - short-period: SM-3, Le3D, CMG-40T
- broad-band: STS-2
• Sampling frequency - 100 Hz, 20 Hz
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An example of simple waveforms - velocity
Data
V14
12 14 16 18 20 22tim e [s]
N
E
Z
P
S
JABO
12 14 16 18 20 22tim e [s]
N
E
Z
P
S
SPAC
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Data
An example of simple waveforms – displacement
V14
12 14 16 18 20 22tim e [s]
N
E
Z
P
S
JABO
12 14 16 18 20 22tim e [s]
N
E
Z
P
S
SPAC
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Data
S03
An example of complicate waveforms – velocity
20 22 24 26 28tim e [s]
N
E
Z
P
S
DVO D
20 22 24 26 28tim e [s]
N
E
Z
P
H RAD
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Data
An example of complicate waveforms – displacement
S03
20 22 24 26 28tim e [s]
N
E
Z
P
S
D VO D
20 22 24 26 28tim e [s]
N
E
Z
P
H R AD
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Data
48 .5 48 .6 48 .7 48 .8 48 .9 49tim e [s]
N
E
Z
P+
H O ST
velocity displacement
48 .5 48 .6 48 .7 48 .8 48 .9 49tim e [s]
N
E
Z
P +
HO ST
40 .9 41 41 .1 41 .2 41.3 41 .4tim e [s]
N
E
Z
P+
PVES
velocity displacement
40 .9 41 41 .1 41 .2 41 .3 41 .4tim e [s]
N
E
ZP+
PVES
Clear polarity identification
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Datavelocity displacement
42 .3 42 .4 42 .5 42.6 42.7 42 .8tim e [s]
N
E
Z
P - ?
SM O L
42 .3 42 .4 42 .5 42 .6 42.7 42 .8tim e [s]
N
E
Z
P - ?
SM O L
velocity displacement
48 48 .1 48 .2 48 .3 48 .4 48 .5tim e [s]
N
E
ZP + ?
K O LL
48 48 .1 48 .2 48 .3 48 .4 48 .5tim e [s]
N
E
ZP + ?
KO LL
Problematic polarity identification
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Direct versus head waves
Data
54.4 54.8 55.2 55.6 56tim e [s]
N
E
Z
Ph+
BO RY
P-
57.2 57.6 58 58 .4 58.8tim e [s]
N
E
Z
P h-
M IC H
P +
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Locations: Epicentres
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Locations: Hypocentres
V03
Latitude [°]Longitude [°]
Depth of hypocentre [km
]
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• FOCMEC (Snoke, 2003): inversion from P-wave polarities
• AMT (Vavryčuk, 2008): inversion from P-wave amplitudes
• ISOLA (Sokos & Zahradník, 2009): inversion from seismograms
Method FOCMEC AMT ISOLAevents 16 36 43
Focal Mechanisms and Moment Tensors
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ISOLA - AMT – FOCMEC – All Events
N = 35 N = 16N = 41
AMT ISOLA FOCMEC
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-100 -80 -60 -40 -20 0 20 40 60 80 100
CLVD [% ]
0
4
8
12
Num
ber o
f eve
nts
-100 -80 -60 -40 -20 0 20 40 60 80 100
ISO [% ]
0
4
8
12
Num
ber o
f eve
nts
-100 -80 -60 -40 -20 0 20 40 60 80 100
CLVD [% ]
0
2
4
6
8
Num
ber o
f eve
nts
-100 -80 -60 -40 -20 0 20 40 60 80 100
ISO [% ]
0
4
8
12
16
Num
ber o
f eve
nts
Non-DC Components
AMT ISOLA
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Non-DC Components
-80 -60 -40 -20 0 20 40 60 80
CLVD [% ]
-60
-40
-20
0
20
40
60
ISO
[%]
-80 -60 -40 -20 0 20 40 60 80
CLVD [% ]
-60
-40
-20
0
20
40
60
ISO
[%]
a) b)AMT ISOLA
Correlation k=0.7vp/vs= 1.46
Correlation k=0.3 vp/vs= 1.57
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Conclusions
• Focal mechanism determined using three different methods are statistically similar
• The majority of mechanisms have the P axes clustered in the NE direction
• The positive correlation between ISO and CLVD can be an indicator of tensile faulting
• The positive values of ISO and CLVD can be an indicator of opening of faults
• The ISO/CLVD ratio yields the vp/vs ratio in the range of 1.46 -1.57
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November 25, 2009, Praha
Thank you for your attention