Deep-sea turbidites have been utilized to understand the history of past large earthquakes. Surface-sediment remobilization is considered to be a mechanism for the initiation of earthquake-induced turbidity currents, based on the studies on the event deposits formed by recent great earthquakes, such as the 2011 Tohoku-oki earthquake, although submarine slope failure has been considered to be a major contributor. However, it is still unclear that the surface-sediment remobilization has actually occurred in past great earthquakes. We examined a sediment core recovered from the mid-slope terrace (MST) along the Japan Trench to find evidence of past earthquake-induced surface-sediment remobilization. Coupled radiocarbon dates for turbidite and hemipelagic muds in the core show small age differences (less than a few 100 years) and suggest that initiation of turbidity currents caused by the earthquake-induced surface-sediment remobilization has occurred repeatedly during the last 2300 years. On the other hand, two turbidites among the examined 11 turbidites show relatively large age differences (~ 5000 years) that indicate the occurrence of large sea-floor disturbances such as submarine slope failures. The sedimentological (i.e., of diatomaceous nature and high sedimentation rates) and tectonic (i.e., continuous subsidence and isolated small basins) settings of the MST sedimentary basins provide favorable conditions for the repeated initiation of turbidity currents and for deposition and preservation of fine-grained turbidites. The MST small basin is a suitable site for examining deep-sea turbidite paleoseismology.

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大地震沿日本海沟陆坡重复发生地表沉积物再活化

深海浊积岩已被用于了解过去大地震的历史。根据对近期大地震（如 2011 年东北大地震）形成的事件沉积物的研究，地表沉积物再活化被认为是引发地震引起的浊流的机制，尽管已考虑海底斜坡破坏成为主要贡献者。然而，目前尚不清楚地表沉积物的再活化是否在过去的大地震中发生过。我们检查了从日本海沟中坡阶地 (MST) 中回收的沉积物核心，以寻找过去地震引起的地表沉积物再动员的证据。核心中浊积岩和半远洋泥浆的耦合放射性碳测年显示出小的年龄差异（小于几百年），表明地震引起的地表沉积物再动员引起的浊流在过去 2300 年中反复发生。另一方面，被检查的 11 个浊岩中的两个浊岩显示出相对较大的年龄差异（约 5000 年），表明发生了大的海底扰动，例如海底斜坡破坏。MST 沉积盆地的沉积（即硅藻性质和高沉积速率）和构造（即连续下沉和孤立的小盆地）环境为浊流的反复启动和细粒沉积物的沉积和保存提供了有利条件。浊流。