09:30 〜 09:45
[MIS13-03] 三陸海岸北部～中部における古津波履歴の高確度復元
キーワード：津波堆積物、放射性炭素年代測定、三陸海岸
Estimating heights and frequency of paleotsunami are important issues for future hazard assessment. The height of paleotsunami is often estimated from the distribution limit of tsunami deposits that were formed by the same tsunami. The distribution limit of paleotsunami can be estimated by age correlation results of tsunami deposits. However, several problems (e.g., erosion by tsunami, preservation potential of tsunami deposit) make it difficult to correlate tsunami deposits by their ages. Here we show the importance of high-resolution radiocarbon dating of sediment which includes tsunami deposits to secure a continuity of geological record based on Ishizawa et al. (2022). The study area is Noda on the northern Sanriku coast of Japan where a paleotsunami history has not been well established. At the study area, we confirmed the continuity of geological records for 400-2700 years ago by high-resolution and sequential radiocarbon dating at potentially inundated only by large tsunamis. Then, paleotsunami history was estimated by the ages of tsunami deposit within the continuous geological records. Our results suggested that the 1611 Keicho tsunami was large tsunami equivalent to the 1896 Meiji Sanriku and 2011 Tohoku-oki tsunamis at the study area. Moreover, we could not find the 1454 Kyotoku tsunami deposit within the continuous geological records at the study area. By combining the results with the paleotsunami history of surrounding areas, we reconstructed the paleotsunami history of widely comparable tsunami deposits on the northern to central Sanriku coast. Our results also suggested that the large tsunami interval at the northern to central Sanriku coast is greater during the past 400 years than it was earlier. We will also discuss the comparison of the paleotsunami history between the Sanriku Coast and the Sendai Plain.