Meeting of Young Scientist BALATONFŐ LINE IN ULTRAHIGH-RESOLUTION: A NEOTECTONIC FAULT ZONE UNDER LAKE BALATON Ferenc Visnovitz Doctoral School of Environmental Sciences Eotvos Lorand University Budapest, Hungary Meeting of Young Scientist Békéscsaba 5th April , 2013

THE STUDY AREA: LAKE BALATON 2 Székely, B. & Molnár, G. 2008

Principle of single channel water seismic imaging WATER SEISMIC INVESTIGATIONS IN THE AREA LAKE BALATON Tóth et al. 2010 Single channel surveys: Instrument: SEISTEC™ Source: boomer Resolution: 0.1 m Penetration: 5-40 m Positioning: DGPS Multichannel surveys: Instrument: Streamer Source: Air-gun Resolution: 1-10 m Penetration: 100-500 m Positioning: DGPS Principle of single channel water seismic imaging Reflections of acoustic waves are dermined by acoustic impedance contrasts 3

MAIN STRATIGRAPHIC UNITS IN SINGLE CHANNEL SEISMIC SECTIONS (vertical exaggeration: x50) The typically observed stratigrapic units under Lake Balaton: horizontally stratified mud (mostly Holocene ~ 0 to15 kyr) cross-bedded Pleistocene fluvial sediments Pannonian deposits: faulted and folded (!) 4

about 1300 km single channel about 500 km multichannel profiles AVAILABLE WATER SESIMIC PROFILES about 1300 km single channel & about 500 km multichannel profiles 5

MAXIMUM HORIZONTAL STRESS ORIENTATIONS IN THE TRANSDANUBIA Northern part (TDR): East-West oriented maximal horizontal stress Southern part (Somogy ): North-South oriented maximal horizontal stress Balaton: transition zone? 6 Bada et al 2010

(BIDDLE & CHRISTIE-BLICK 1985) GENERAL MODEL OF A LEFT LATERAL SHEAR ZONE EXPECTED IN THE AREA (BIDDLE & CHRISTIE-BLICK 1985) Modified after Biddle & Christie- Blick 1985 7

EXAMPLE TO ILLUSTRATE NATURE OF FAULT UNDER LAKE BALATON 1 EXAMPLE TO ILLUSTRATE NATURE OF FAULT UNDER LAKE BALATON 1. (SIÓFOK BASIN) 8

EXAMPLE TO ILLUSTRATE NATURE OF FAULT UNDER LAKE BALATON 2 EXAMPLE TO ILLUSTRATE NATURE OF FAULT UNDER LAKE BALATON 2. (SIÓFOK BASIN) 9

EXAMPLE TO ILLUSTRATE NATURE OF FAULT UNDER LAKE BALATON 3 EXAMPLE TO ILLUSTRATE NATURE OF FAULT UNDER LAKE BALATON 3. (SZEMES BASIN) 10

Fault indication map for the Eastern half of Lake Balaton (2013) THE MAP VIEW OF FAULTS IDENTIFIED ON SEISMIC PROFILES Fault indication map for the Eastern half of Lake Balaton (2013) 11

NEW RESULTS: INTERPRETED FAULTS IN THE AREA OF THE SIÓFOK AND SZEMES BASIN 12

OVERVIEW OF THE MAIN DISPLACEMENT ZONES BASED ON INTERPRETED FAULTS AND THEIR ORIENTAION IN THE RECENT STRESS FIELD 13

SUGGESTED LEFT LATERAL ZONES WITH DISPLACEMENT DUPLEXES 14

SUMMARY AND CONCLUSIONS As consenquence of the recent stress field (with NE-SW oriented maximal princilpal stress) a left lateral strike slip zone formed in the area of Lake Balaton that manifested in faults almost parallel to the lake’s longitudinal axis. Left lateral displacement zones are joining in the deeper part of the Balatonian basins where we observed strongly deformed structural blocks (tectonic displacement duplexes). Orientation of en-echelon folds also confirm strike-slip nature of the fault systems (not presented here). Our conclusion is that formation of the lake is not a result of a trench collapse mechaisms. „Prebalatonian” basins have developed in a zone weakened by strike slip tectonics where deflation and fluvial erosion could create deeper depressions. 15

Thank you for your kind attention! Acknowledgement New seismic surveys (2011-2012) were supported by NK83400 OTKA fund. Seismic sections have been recorded in cooperation with Geomega. Measurements were helped by students of Eotvos University. Special thanks to Attila Balázs for his help in seismic processing. Thanks for Association of Hungarian Geophysicists for financing conference fees. And finally… Thank you for your kind attention! References: BADA G., SZAFIÁN P., VINCZE O., TÓTH T., FODOR L., SPIESS, V. & HORVÁTH F. 2010 Neotektonikai viszonyok a Balaton keleti medencéjében és tágabb környezetében nagyfelbontású szeizmikus mérések alapján In: Földtani Közlöny, 140/4, 367-390. BIDDLE, K.T., CHRISTIE-BLICK, N. 1985. Glossary (strike-slip deformation, basin formation and sedimentation). In: Biddle, K.T., Christie-Blick, N. (eds.): Strike-Slip Deformation, Basin Formation and Deformation. - Society of Economic Paleontologists and Mineralogists, Special Publication 37, 375-385, Tulsa, Oklahoma. SACCHI, M. 2001. Late Miocene evolution of the Western Pannonian basin, Hungary. In: Doktori (PhD) értekezés, ELTE TTK Geofizikai Tanszék, Budapest. SZÉKELY, B. & MOLNÁR, G. 2008. Do the post-Miocene volcanic features really mark a single paleoaltitude in the Transdanubian Range (Pannonian basin)? In: Geophysical Research Abstracts, 10: 11566. ISSN 1029-7006 TÓTH ZS., TÓTH T., SZAFIÁN P., HORVÁTH A., HÁMORI Z., DOMBRÁDI E., FEKETE N., SPIESS V. & HORVÁTH F. 2010. Szeizmikus kutatások a Balatonon In: Földtani Közlöny 140/4, 355-365. VISNOVTZ F ÉS A BALATONI SZEIZMIKUS KUTATÓCSOPORT 2012. Késő-miocén üledékrétegek szeizmikus kutatása a Balaton középső medencéjében In: Környezettudományi Doktori Iskolák konferenciája kiadvány, ISBN 978-963-284-242-4, p. 12-19. 16