Tsunami backwash deposits on the Algarve continental shelf

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Tsunami research has become prominent within geosciences, especially following the recent tsunami events in the Indian Ocean (2004 Sumatra) and in Japan (2011 Tohoku-Oki). Events like these are unpredictable, catastrophic and responsible for severe damages to infrastructures and loss of lives. Consequently, the sedimentological analysis of (palaeo)tsunami deposits has become a key factor for the evaluation of tsunami risk to coastal communities and can eventually help to mitigate impacts. Even though the field of tsunami science and sedimentology showed substantial progress during the last decades, many tsunami characteristics and related processes, especially regarding the hydrodynamics of tsunami backwash flows, are still poorly understood. In this project, we like to investigate offshore c. 80 m of cores taken in two transects perpendicular to the Algarve coast off Portugal during cruise M152 (RV METEOR) by vibracoring by a multiproxy approach including sedimentology, geochemistry, dating and palaeontology. Work packages include the a) identification of suitable proxies for the characterisation of tsunami deposits in the offshore deposits of the Algarve shelf until ca. 100 m water depth; b) the determination of potential sediment sources (e.g., beach, dune, nearshore) for the offshore tsunami deposits, c) the reconstruction of the transport paths to achieve a comparison of the characteristics of onshore and offshore tsunami deposits; and lastly, d) the mapping of the spatial distribution of tsunami backwash deposits along the Algarve shelf including hydroacoustic data obtained during the cruise. These data are needed for a later modelling of hydrodynamic processes of tsunami backwash from the coast towards the offshore. As the Algarve was intensely affected by the AD1755 Lisbon tsunami, and, probably an earlier event ca. 3.7 kyr ago, and we already identified the events in sediment cores, we aim to synthesize the data of the shelf. Our scientific hypotheses include the development of tools for historical and prehistoric tsunamis that helps to detect and evaluate these events off-shore world-wide and to set up general models for distribution modes of back wash sediments.