Abstract In 1960 CE, Lake Cucao on Chiloe Island in south central Chile was inundated by the tsunami of the Great Chilean Earthquake (Mw 9.5). The area of what is now the lake basin has been submerged since the end of the rapid postglacial sea-level rise and has recorded tsunami inundations in its sediment record since then. This study reconstructs the tsunami history of Lake Cucao. Reflection-seismic profiles and side scan sonar data of the lake reveal a tidal delta with a crosscutting channel, which controls the sedimentary environment in the coast-facing part of Lake Cucao. The convergent pattern of seismic reflections near this channel indicates that tidal currents were active in the lake at least episodically since the formation of a major unconformity with strong reflection amplitude, which records the onset of lacustrine sedimentation. A radiocarbon date at the base of one of the 21 collected sediment cores dates this reflector to ~3800 years BP. Little net vertical displacement (≤2 m) in combination with an outlet river channel that can act as a pathway for sediment transport appears to have maintained the sensitivity of Lake Cucao to record tsunami inundation. The sedimentary record contains 15 clastic layers which are interpreted as tsunami deposits. The confidence level on the tsunami interpretation depends on five site-specific criteria, which are: (i) high magnetic susceptibility of the sediment indicating high clastic content, (ii) cross core correlation indicating widespread deposition, (iii) acoustic reflector correlation to the sedimentary record (also indicating widespread deposition), (iv) presence of mud clasts, and (v) age correlation to known paleotsunamis in the area. In this way, eight clastic layers are interpreted as tsunami deposits with a high confidence level, five with a medium confidence level and two with a relatively low confidence level. This study adds a long paleotsunami record on a coastline where extreme tsunamis occur frequently and where long (>2000 years) paleotsunami records are still sparse.

中文翻译：

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智利中南部奇洛埃岛库考湖复杂沿海湖泊系统过去4300年的古海啸记录

摘要 公元 1960 年，智利中南部奇洛埃岛上的库考湖被智利大地震（Mw 9.5）的海啸淹没。自冰后海平面快速上升结束以来，现在的湖盆区域已被淹没，此后沉积物记录中记录了海啸淹没。这项研究重建了库曹湖的海啸历史。该湖的反射地震剖面和侧扫声纳数据揭示了一个具有横切通道的潮汐三角洲，它控制着库曹湖面向海岸部分的沉积环境。该河道附近地震反射的会聚模式表明，自从形成具有强反射幅度的主要不整合面以来，潮汐流至少偶尔在湖中活跃，这记录了湖相沉积的开始。收集到的 21 个沉积物岩心之一底部的放射性碳日期将该反射器的年代确定为约 3800 年 BP。极小的净垂直位移 (≤2 m) 与可作为沉积物运输通道的出口河道相结合，似乎保持了库曹湖对记录海啸淹没的敏感性。沉积记录包含 15 个碎屑层，这些碎屑层被解释为海啸沉积物。海啸解释的置信水平取决于五个特定地点的标准，它们是：(i) 沉积物的高磁化率，表明碎屑含量高，(ii) 跨核相关性表明广泛的沉积，(iii) 声学反射器与沉积记录（也表明广泛的沉积），（iv）泥屑的存在，(v) 与该地区已知古海啸的年龄相关性。这样，八个碎屑层被解释为具有高置信度的海啸沉积物，五个具有中等置信度，两个具有相对较低的置信度。本研究在极端海啸频繁发生且长期（> 2000 年）古海啸记录仍然稀少的海岸线上添加了长古海啸记录。