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Current status of palaeoseismic research along the Nankai Trough, Japan

TitleCurrent status of palaeoseismic research along the Nankai Trough, Japan
Publication TypeConference Paper
Year of Publication2015
AuthorsGarrett, E, Garrett, P, Fujiwara, O, Heyvaert, VMA, Shishikura, M, De Batist, M, Yokoyama, Y
Conference NameGeological Society Arthur Holmes meeting on Tsunami Hazards and Risks
Conference LocationLondon, UK
Abstract

In the wake of the devastating 2011 Tōhoku earthquake and tsunami, the Central Disaster Management Council of the Japanese Cabinet Office issued new guidance for assessing seismic hazards in Japan. Following the unexpectedly large magnitude of the earthquake and the size of the tsunami, the Cabinet Office advocated renewed investigation of earthquake and tsunami occurrence timescales exceeding the historical period, with a particular focus on defining the largest possible magnitudes. The new guidelines pay close attention to the Nankai Trough, the subduction zone where the Philippine Sea Plate dives beneath the Eurasian Plate. The Nankai Trough faces the densely populated and highly industrialised coastline of south central Japan. Here, we review geological evidence for past earthquakes and tsunamis along this subduction zone. This evidence comes from a wide variety of sources, including uplifted marine terraces, turbidites, liquefaction features, subsided marshes and tsunami deposits in coastal lakes and lowlands. More than 70 sites yield evidence, however the number of events recorded at each site varies depending on site-specific evidence creation and preservation thresholds. The longest record exceeds ten thousand years, however the majority are less than four thousand years long. Our compilation suggests that earthquakes in AD 684 and 1361 were similar predecessors of the AD 1707 earthquake, widely regarded as the largest event of the historical period. The more limited distribution of evidence for other historical earthquakes highlights the variability in rupture mode that characterises the Nankai Trough. The palaeoseismic catalogue is, however, limited due to issues over alternative hypotheses for proposed palaeoseismic evidence, poor chronological control and sampling approached insufficient to address the recurrence of the largest past earthquakes and tsunamis. We highlight recent advances and propose future directions for Nankai Trough palaeoseismology.

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