Abstract This paper reviews recent progress in tsunami geology and the history of coastal uplift/subsidence along the Pacific coasts of Hokkaido and Tohoku, facing the Kuril and Japan Trenches, respectively. In the last 20 years, research by tsunami geologists in northeast Japan has focused on extending the record of tsunamis beyond the range of historical documents in the region, which span too little time to reveal much of the earthquake history over the last millennia. Along the coast of Hokkaido, recurrent sandy deposits are evidence of historical and prehistoric large tsunamis. At Kiritappu marsh, for example, at least 15 identified tsunami deposits occurred between 200 and 6,000 years ago. The spatial distribution of the most recent prehistoric tsunami deposit, that of the so-called 17th-century earthquake and tsunami, exceeds historical and recent tsunami inundations in eastern Hokkaido. Numerical simulations of this event require a multi-segment fault model with variable slip (Mw > 8.8) encompassing both the Tokachi-oki and Nemuro-oki regions to reproduce the observed deposit distribution in eastern Hokkaido. The recurrence interval of such multi-segment earthquakes along the southern Kuril Trench is estimated to be 100–800 years based on tephrochronological and radiocarbon evidence. Tsunami deposits are also associated with historical earthquakes in 1843 and 1894 in eastern Hokkaido and with the 1640 Komagatake eruption in western Hokkaido. The 17th-century earthquake probably triggered postseismic coastal deformation. Diatom-based transfer functions suggest rapid subsidence before the event and gradual uplift afterward, and historical volcanic ash layers indicate that gradual postseismic uplift occurred over decades. A simple dislocation model can explain such gradual uplift as an aseismic fault extension after the 17th-century event. In the Tohoku region, a tsunami deposit associated with the 869 Jogan earthquake has been identified, and the inundation area of this event has been constrained based on the lateral extent of the tsunami deposit and its stratigraphic position beneath the historical To-a tephra (915 CE). Land-level changes at Odaka, Fukushima prefecture, associated with the Jogan event have been estimated based on changes of fossil diatom assemblages below and above the tsunami deposit. Numerical simulations based on geological evidence and observations of the 2011 Tohoku tsunami deposit suggest that the Jogan event was a plate-boundary rupture at least 200 km long along the Japan Trench (Mw > 8.3–8.6). The 1454 Kyotoku tsunami is also considered to have been generated by a rupture area including the Miyagi-oki region (part of the Jogan rupture). It remains unclear whether the 869, 1454, and 2011 tsunamis were similar in size and source; if they were, the recurrence intervals of such events near Sendai are less than 600 years and more regular than those for multi-segment earthquakes along the Kuril Trench.

中文翻译：

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日本东北太平洋沿岸俯冲带古地震学——进展与遗留问题

摘要 本文回顾了海啸地质学的最新进展以及北海道和东北太平洋沿岸分别面向千岛海沟和日本海沟的海岸隆起/沉降历史。在过去的 20 年中，日本东北部海啸地质学家的研究重点是将海啸记录扩展到该地区历史文献范围之外，因为时间太短，无法揭示过去数千年的大部分地震历史。沿着北海道海岸，反复出现的沙质沉积物是历史和史前大型海啸的证据。例如，在 Kiritappu 沼泽地，至少有 15 个已确定的海啸沉积物发生在 200 至 6,000 年前。最近的史前海啸沉积物的空间分布，即所谓的 17 世纪地震和海啸的空间分布，超过了北海道东部历史和最近的海啸洪水。该事件的数值模拟需要一个包含十胜冲和根室冲地区的可变滑移（Mw > 8.8）的多段断层模型，以重现北海道东部观察到的沉积物分布。根据地质年代学和放射性碳证据，这种沿千岛海沟南部发生的多段地震的复发间隔估计为 100-800 年。海啸沉积物还与 1843 年和 1894 年北海道东部的历史地震以及 1640 年北海道西部的驹岳火山喷发有关。17 世纪的地震可能引发了地震后的海岸变形。基于硅藻的传递函数表明事件发生前快速下沉，之后逐渐上升，历史上的火山灰层表明地震后的隆升已经发生了几十年。一个简单的错位模型可以解释 17 世纪事件后地震断层延伸这样的逐渐抬升。在东北地区，已确定与 869 年 Jogan 地震相关的海啸沉积物，并根据海啸沉积物的横向范围及其历史悠久的 To-a tephra (915行政长官）。与 Jogan 事件相关的福岛县小高的土地水平变化是根据海啸沉积物下方和上方的化石硅藻组合的变化来估计的。基于地质证据和 2011 年东北海啸沉积物观测的数值模拟表明，Jogan 事件是沿日本海沟（Mw > 8.3-8.6）至少 200 公里长的板块边界破裂。1454 年的京都海啸也被认为是由包括宫城冲地区（长岩破裂的一部分）在内的破裂区域产生的。目前尚不清楚869、1454和2011海啸的规模和来源是否相似；如果是的话，仙台附近此类事件的复发间隔不到600年，而且比千岛海沟沿线的多段地震更规律。目前尚不清楚869、1454和2011海啸的规模和来源是否相似；如果是的话，仙台附近此类事件的复发间隔不到600年，而且比千岛海沟沿线的多段地震更规律。目前尚不清楚869、1454和2011海啸的规模和来源是否相似；如果是的话，仙台附近此类事件的复发间隔不到600年，而且比千岛海沟沿线的多段地震更规律。