Download Document

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
Székely, B. & Molnár, G. 2008
2
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
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): EastWest oriented maximal
horizontal stress
Southern part (Somogy ):
North-South oriented
maximal horizontal stress
Balaton: transition zone?
Bada et al 2010
6
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. (SIÓFOK BASIN)
8
EXAMPLE TO ILLUSTRATE NATURE OF FAULT
UNDER LAKE BALATON 2. (SIÓFOK BASIN)
9
EXAMPLE TO ILLUSTRATE NATURE OF FAULT
UNDER LAKE BALATON 3. (SZEMES BASIN)
10
0
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, 375385, 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