Abstract Historical documents indicate that the AD 1611 Keicho earthquake tsunami struck the Pacific coast of Tohoku, northern Japan. Meanwhile, geological records suggest that a large earthquake occurred along the Kuril Trench in the same century. Although historians and geologists have investigated the events intensively, understanding of those events remains insufficient because of limited evidence. As described herein, we suggest future research directions for the huge seventeenth-century tsunamis based on a comprehensive review of earlier works and simulation of the directivity of tsunamis. Our results suggest the possibility that one extremely large or two or three closely spaced large earthquakes and tsunamis occurred in a short time interval along the Kuril and Japan trenches. If this is the case, we must devote attention to the risk of a future occurrence of a Kuril Trench event because the situation after the AD 2011 Tohoku-oki tsunami might be similar to the seventeenth-century events. The key research directions to clarify the seventeenth-century events are a careful review of historical documents during several decades after the AD 1611 earthquake and accurate constraint of the event age of tsunami deposits.

Abstract The 2011 Tohoku earthquake, tsunami and resulting damage is often referred to as 3.11 after the date on which it took place. Leading to almost 20 000 people dead or missing, a major nuclear disaster and severe economic damage, 3.11 represents the biggest challenge faced by Japan since the end of World War II. Before 3.11, the possibility of a Mw 9 earthquake in this area was not generally recognized, highlighting the need to reassess seismic risk in NE Japan. The large amount of new quantitative data covering a range of disciplines and from onshore and offshore studies makes 3.11 an important case study that can contribute to improving our understanding of tsunamis, including their formation, their effects on coastal regions and the effectiveness of defensive measures old and new. Geological studies have a key role to play in this new phase of tsunami studies and this is the only method available for determining recurrence intervals over timescales of thousands of years. Data from 3.11 have improved our ability to identify sedimentary records of tsunami events and to estimate tsunami size from geological data. More complete databases will provide invaluable information for long-term planning of coastal regions in convergent plate margins.

Abstract A thick, calcareous, clastic megabed of late Maastrichtian age has been known for sometime in western and central Cuba. This megabed was formed in association with the bolide impact at Chicxulub, Yucatán, at the K/T boundary, andiscomposed of a lower gravity-flow unit and an upper homogenite unit. The lower gravity-flow unit is dominantly composed of calcirudite that was formed because of collapses of the Yucatán, Cuban, and Bahamian platform margins and subsequent accumulation in the lower slope to basin margin environment. The gravity flow probably was triggered by a seismic wave induced by the impact, although a ballistic flow may have triggered collapse in the case of proximal sites (Yucatán margin). The upper homogenite unit is composed of massive and normally graded calcarenite to calcilutite that was formed as a result of large tsunamis associated with the impact and deposited in wider areas in the deeper part of Paleo-western Caribbean basin. Slight grain-size oscillations in this unit probably reflect the influence of repeated tsunamis. The large tsunamis were generated either by the movement of water into and out of the crater cavity or by the large-scale slope failure on the eastern margin of the Yucatán platform. In upper slope to shelf environments, gravity-flow deposits and homogenite are absent, and a thin sandstone complex influenced by repeating tsunami waves was deposited.

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