The east coast of Japan is prone to tsunamigenic megathrust earthquakes, as tragically demonstrated in 2011 by the Tōhoku earthquake (Mw 9.0) and tsunami. The Nankai Trough subduction zone, to the southwest of the area affected by the Tōhoku disaster and facing the densely populated and heavily industrialized southern coastline of central and west Japan, is also expected to generate another great megathrust earthquake and tsunami in the near future. Historical records suggest the subduction zone segmented and characterized by a variable rupture mode, involving single- as well as multi-segment ruptures, with immediate implications for the tsunamigenic potential. This renders the collection of sufficiently long records of past earthquakes and tsunami in this region fundamental for adequate hazard and risk assessment. In response to the 2011 Tōhoku earthquake, the Cabinet Office of the Japanese government proposed new guidelines for assessing the risk of similar earthquakes affecting the Nankai subduction zone (Central Disaster Management Council, 2011). These guidelines advocate renewed investigation of earthquake and tsunami occurrence over historical and longer timescales, with a particular focus on defining the largest possible magnitudes. The QuakeRecNankai project contributes to this goal by generating a long and coherent time series of megathrust earthquake and tsunami recurrences along the Nankai Trough subduction zone by integrating all existing evidence with new geological records of paleo-tsunami in the Lake Hamana region and of paleo-earthquakes from selected lakes in the Mount Fuji area. We combine extensive fieldwork in coastal plain areas and lakes with advanced sedimentological and geochemical analyses and innovative dating techniques.
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