Tsunami history and turbidite paleoseismology of the Mentawai Patch, west Sumatra

如果苏门答腊岛近海明打威群岛的地震间隙完全破裂，将导致8.7-9.0级地震，极有可能引发破坏性极大的海啸，威胁到沿海社区，包括拥有100万居民的巴东市。然而，在沉积物丰富的苏门答腊西海岸和帕丁岛的北部和南部，并没有已知的海啸沉积物，当地对以前海啸淹没的了解也很少。这个拟议的研究项目包括两个主要工作包。首先，我们将利用现有的海上地球物理数据和沉积物岩心来测试浊积岩古地震学是否可以成功地应用于西苏门答腊近海明打威海相前弧盆地。这一部分依赖于先前获得的地球物理数据和现有的沉积物岩心。明打威盆地的沉积环境在浊积岩古地震学研究中从未被测试过。这些结果很有可能揭示千年尺度的地震记录。其次，将近海浊积岩古地震学研究与陆上海啸沉积分析相结合。这项研究将依赖于在广泛的野外工作中从沿海沉积物中获得的一组约10米长的锤式岩心。这些岩心将用于揭示巽他弧俯冲带的地震活动（来自历史记录、已建立的珊瑚档案和我们新的浊积岩古地震记录）与苏门答腊中部西海岸海啸危险之间的关系。揭示巴东周边地区的海啸历史对这个沿海社区至关重要，因为这个社区几代人都没有遭受过大海啸的袭击，与2004年印度洋大海啸之前亚齐地区的沿海社区非常相似。该项目的创新之处包括：(1)为浊积岩古地震学的成功应用而测试前弧盆地环境；(2)调查明打威海岸沉积古海啸记录；(3)整合陆上和海上记录；(4)将所有这些记录与其他古地震记录综合起来，例如明打威群岛珊瑚的同震变形记录。这种创新的方法将对沿俯冲带的地震活动、海洋环境中的重力流、同震海岸变形和海啸地质灾害潜力之间的关系产生重要的见解。

A full-release rupture of the seismic gap on the Mentawai Patch offshore Sumatra would result in an M 8.7–9.0 earthquake, which would most likely induce a highly destructive tsunami threatening coastal communities, including the city of Padang with >1 million inhabitants. However, there are no known tsunami deposits along the sediment-rich Sumatran west coast north and south of Padng, and local knowledge about previous tsunami inundations is sparse.This proposed research project consists of two main work packages. First, we will use existing offshore geophysical data and sediment cores to test whether turbidite-based paleoseismology can be successfully applied in the marine forearc Mentawai Basin offshore west Sumatra. This part relies on previously obtained geophysical data and existing sediment cores. The sedimentary environment of the Mentawai Basin has never been tested before for turbidite-based paleoseismology. The results hold a strong potential to reveal a millennial-scale record of earthquake shaking. Second, the offshore turbidite paleoseismology study will be coupled with the analysis of onshore tsunami deposits. This research will rely on a set of ~10m long hammer cores from coastal sediments acquired during an extensive fieldwork campaign. These cores will be used to reveal the relationship between seismic activity of the Sunda Arc subduction zone (from historical records, established coral archives and our novel turbidite paleoseismological record) and tsunami hazard along the central Sumatran west coast. Revealing the tsunami history of the region around Padang is of utmost importance to this coastal community that has not been hit by a large tsunami in generations – quite similar to the coastal communities of the Aceh region before the giant Indian Ocean tsunami of 2004.The innovation of this project entails i) the test of a forearc-basin setting for the successful application of turbidite paleoseismology, ii) the investigation of sedimentary paleotsunami records along the coast of the Mentawai Patch, iii) the integration of onshore and offshore records, and iv) the synthesis of all the former with other paleoseismological records, e.g. co-seismic deformation records of corals along the Mentawai Islands. This innovative approach will yield important insights into the relationships between seismic activity along a subduction zone, gravity flows in the marine environment, co-seismic coastal deformation and tsunami geohazard potential.