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 9 th 1906 – the strongest earthquakes in the region in 20 th century Ms = 5.7; h=15 km, epicentral intensity Io = 8° MSK-64 Period:
Seismic Stations Seismic stations in Slovakia National seismic network Local seismic network LSSVS Local seismic network EBO Local seismic network EMO
Geological Map
Tectonic Sketch
P-wave Velocity Model 3D 1D
Data 44 micro-earthquakes Period 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 Hz, 20 Hz
An example of simple waveforms - velocity Data V14
Data An example of simple waveforms – displacement V14
Data S03 An example of complicate waveforms – velocity
Data An example of complicate waveforms – displacement S03
Data Clear polarity identification
Data Problematic polarity identification
Direct versus head waves Data
Locations: Epicentres
Locations: Hypocentres V03 Latitude [°] Longitude [°] Depth of hypocentre [km]
FOCMEC (Snoke, 2003): inversion from P-wave polarities AMT (Vavryčuk, 2008): inversion from P-wave amplitudes ISOLA (Sokos & Zahradník, 2009): inversion from seismograms MethodFOCMECAMTISOLA events Focal Mechanisms and Moment Tensors
ISOLA - AMT – FOCMEC – All Events N = 35N = 16N = 41 AMT ISOLA FOCMEC
Non-DC Components AMT ISOLA
Non-DC Components AMT ISOLA Correlation k=0.7 v p /v s = 1.46 Correlation k=0.3 v p /v s = 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 v p /v s ratio in the range of
November 25, 2009, Praha Thank you for your attention