Sublacustrine landslides and associated hazards along the Western Slope of Lake Ohrid (Macedonia/Albania).

Grün, Matthias (2011) Sublacustrine landslides and associated hazards along the Western Slope of Lake Ohrid (Macedonia/Albania). (Master thesis), Christian-Albrechts-Universität zu Kiel, Kiel, 111 pp.

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Abstract

Submarine mass failures are very complex features and studying their processes is of great importance as they imply mayor geohazards. Their effects range from erosion of submarine slope areas over destruction of offshore infrastructure to the generation of tremendous tsunamis. In general submarine mass failures occur along continental margins or ocean island flanks but are also observed in fjords or lakes. Lake Ohrid (Macedonia/Albania) is situated in a tectonic active region surrounded by high and steep mountain chains. Numerous mass wasting deposits have been detected inside the lake through different geophysical surveys including side‐scan and seismic and sediment echo sounder measurements. The BLOSSOM campaign of September/October 2009 additionally provided high resolution bathymetry of Lake Ohrid. Relatively young sub aquatic landslides were found at the steep western slope at the lake at the transition to the plain Central Basin in nearly 250 m depth. The largest mass movement that occurred in the lake is the so called Udenisht Slide at the south western margin of the lake. High resolution bathymetric data allows close analysis of slide specific features. Indicated by sidewalls of 20 m in height, more than 100∙10 6 m3 of material was removed during this event together with numerous large blocks that have been activated and were transported. Seismic and sediment echo sounder data reveals that this event must have happened not more than 800 years ago and that it had large impact on the whole south western margin as well as the southern part of the Central Basin. Significant erosion took place during the mass movement indicating a high energetic landslide. Analysis of the available data let assume that the large mass movement deposition body probably is the result of two successive slides while the second event was overriding the first deposition and destroying the interface by erosion. Buried mass wasting deposits have been discovered below the Udenisht unit pointing out the unstable condition of the south western part of Lake Ohrid. They also show that mass failure events occur rather irregular. Since earthquakes are the most probable trigger mechanisms for landslides in this seismic active region additional pre‐conditioning factors have been found like the occurrence of gas seepages at the base of the slope, fault zones and undercutting by retrogressive failure slides. While sub aquatic landslides not only affect the lake floor topography but are also able to generate tsunami waves, special interest was given to the question if Udenisht Slide might have released a tsunami. Therefore key parameters of the landslide have been analyzed that influence tsunamigenic potential of sub aquatic landslides. Volume‐to‐wave‐height relations and comparisons with other case studies have been evaluated showing that Udenisht Slide indeed must be considered as a potential tsunami source. This is not only important for the hazard estimation of this particular slide but also shows that for future mass movements in this tectonic active region tsunamis must be taken into account as an additional threat.

Document Type: Thesis (Master thesis)
Thesis Advisor: Krastel-Gudegast, Sebastian
Additional Information: Studiengang Geowissenschaften
Keywords: Meereswissenschaften; Geodynamics; Sublacustrine landslides; hazards; Western slope of Lake Ohrid, Macedonia/Albania
Subjects: Course of study: MSc Geoscience
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-JRG-B4 Submarine Hazards
Projects: Lake Ohrid (1352-KR 222/7-2)
Date Deposited: 03 Feb 2012 10:52
Last Modified: 06 Aug 2024 13:19
URI: https://oceanrep.geomar.de/id/eprint/13639

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