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MICRO-SEISMICITY AND FOCAL MECHANISMS
IN THE MALÉ KARPATY MTS.,
SLOVAKIA
Lucia Fojtíková, Václav Vavryčuk, Andrej Cipciar, Ján Madarás
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
Seismic Stations
Seismic stations in Slovakia
National seismic networkLocal seismic network LSSVSLocal seismic network EBOLocal seismic network EMO
Geological Map
Tectonic Sketch
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 velocity [km /s]
30
20
10
0
Dep
th [k
m]
3D 1D
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
An example of simple waveforms - velocity
Data
V14
12 14 16 18 20 22
tim e [s]
N
E
Z
P
S
JABO
12 14 16 18 20 22
tim e [s]
N
E
Z
P
S
SPAC
Data
An example of simple waveforms – displacement
V14
12 14 16 18 20 22
tim e [s]
N
E
Z
P
S
JABO
12 14 16 18 20 22
tim e [s]
N
E
Z
P
S
SPAC
Data
S03
An example of complicate waveforms – velocity
20 22 24 26 28
tim e [s]
N
E
Z
P
S
DVO D
20 22 24 26 28
tim e [s]
N
E
Z
P
HRAD
Data
An example of complicate waveforms – displacement
S03
20 22 24 26 28
tim e [s]
N
E
Z
P
S
D VO D
20 22 24 26 28
tim e [s]
N
E
Z
P
H RAD
Data
48.5 48.6 48.7 48.8 48.9 49
tim e [s]
N
E
Z
P+
H O ST
velocity displacement
48.5 48.6 48.7 48.8 48.9 49
tim e [s]
N
E
Z
P+
H O ST
40.9 41 41.1 41.2 41.3 41.4
tim e [s]
N
E
Z
P+
PVES
velocity displacement
40.9 41 41.1 41.2 41.3 41.4
tim e [s]
N
E
Z
P+
PVES
Clear polarity identification
Datavelocity displacement
42.3 42.4 42.5 42.6 42.7 42.8
tim e [s]
N
E
Z
P- ?
SM O L
42.3 42.4 42.5 42.6 42.7 42.8
tim e [s]
N
E
Z
P - ?
SM O L
velocity displacement
48 48.1 48.2 48.3 48.4 48.5
tim e [s]
N
E
ZP+ ?
KO LL
48 48.1 48.2 48.3 48.4 48.5
tim e [s]
N
E
Z
P + ?
KO LL
Problematic polarity identification
Direct versus head waves
Data
54.4 54.8 55.2 55.6 56
tim e [s]
N
E
Z
Ph+
BO R Y
P-
57 .2 57.6 58 58.4 58.8
tim e [s]
N
E
Z
Ph-
M IC H
P+
Locations: Epicentres
Locations: Hypocentres
V03
Latitude [°
]Longitude [°]
De
pth
of h
yp
oc
en
tre [k
m]
• 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 ISOLA
events 16 36 43
Focal Mechanisms and Moment Tensors
ISOLA - AMT – FOCMEC – All Events
N = 35 N = 16N = 41
AMT ISOLA FOCMEC
-100 -80 -60 -40 -20 0 20 40 60 80 100
CLVD [% ]
0
4
8
12
Num
ber
of e
vent
s
-100 -80 -60 -40 -20 0 20 40 60 80 100
ISO [% ]
0
4
8
12
Num
ber
of e
vent
s
-100 -80 -60 -40 -20 0 20 40 60 80 100
CLVD [% ]
0
2
4
6
8
Num
ber
of e
vent
s
-100 -80 -60 -40 -20 0 20 40 60 80 100
ISO [% ]
0
4
8
12
16
Nu
mb
er
of
eve
nts
Non-DC Components
AMT ISOLA
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
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
November 25, 2009, Praha
Thank you for your attention
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