Morphodynamics and Slope Stability of the Andaman Sea Shelf Break (Thailand)
Zusammenfassung der Projektergebnisse
In the framework of the German-Thai cooperation on tsunami research TRIAS (Tracing Tsunami Impacts On- and Offshore in the Andaman Sea Region), the MASS project (Morphodynamics and Slope Stability of the Andaman Sea Shelf Break) aimed in assessing the potential risk for tsunamis generated by submarine mass-wasting along the Andaman Sea shelf break off the west coast of Thailand. Sediment echo sounder, bathymetric and highresolution multichannel seismic data were collected during three research cruises on the Thai Research Vessel Chakratong Tongyai. Whereas the top of the Mergui Ridge is characterized by a gentle and smooth morphology, the western rim and the slope displays a rugged and quite instable terrain. The newly collected data allowed the identification of 17 mass transport deposits. Minimum volumes of individual MTDs range between 0.3 km3 and 14 km3. Landslide deposits have been identified in three different settings: (i) stacked MTDs within disturbed and faulted basin sediments at the transition of the East Andaman Basin to the Mergui Ridge; (ii) MTDs within a pile of drift sediments at the basin-ridge transition; and (iii) MTDs near the edge of/on top of Mergui Ridge in relatively shallow water depths (< 1000 m). Our data indicate that the Mergui Ridge slope area seems to have been generally unstable with repeated occurrence of slide events. The most likely pre-conditioning factors for slope instabilities include the presence of unstable drift sediments, excess pore pressure, and active tectonics. We modelled two categories of submarine landslide scenarios in order to assess the tsunamigenic potential of landslides in the Andaman Sea. Geometric parameters of the first category are taken from identified mass transport deposits (MTDs); the second category considers a potentially unstable block identified in seismic data. Our simple modeling approach shows that run-up values may reach significant tsunami heights for some scenario, but we would like to point out that our results have to be regarded as worst case scenarios due to several limitations of our modeling approach. Recurrence rates of landslide are estimated to be in the range of 10 - 100 kyrs, which is very long compared to major tsunamigenic earthquakes occurring in the Sumatra–Andaman area (every 400 – 600 years). Hence, landslide tsunamis do not represent a major additional risk for the Thai coast, but should not be neglected because landslide-triggered tsunamis would hit the coast only 30 minutes after the failure with almost no warning time.
Projektbezogene Publikationen (Auswahl)
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(2011) RV Chakratong Tongyai Fahrtbericht / Cruise Report: MASS-III Morphodynamics and Slope Stability of the Andaman Sea Shelf Break (Thailand), Phuket - Phuket (Thailand), 11.01. - 24.01.2011 IFM-GEOMAR Report 43, 32 pp.
Krastel, S. et al.
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(2012) Morphology of the Andaman outer shelf and upper slope of the Thai exclusive economic zone. Journal of Asian Earth Sciences 46, 78-85
Jintasaeranee, P., Weinrebe, W., Klaucke, I., Snidvongs, A., Flueh, E.
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(2012) Submarine mass wasting and associated tsunami risk offshore western Thailand, Andaman Sea, Indian Ocean. Natural Hazards and Earth System Sciences 12 (8), 2609-2630
Schwab, J., Krastel, S., Grün, M., Gross, F., Pananont, P., Jintasaeranee, P., Bunsomboonsakul, S., Weinrebe, W., Winkelmann, D.
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(2014) Modeling potential tsunami hazards associated with submarine landslides in the East Andaman Basin offshore western Thailand In: Submarine mass movements and their consequences (eds: Krastel et al), Advances in Natural and Technological Hazards Research, 37, 517-528
Schwab, J. Krastel, S., Heidarzadeh, M.
