Paleotsunami history along the northern Japan trench based on sequential dating of the continuous geological record potentially inundated only by large tsunamis
Paleotsunami history along the northern Japan trench based on sequential dating of the continuous geological record potentially inundated only by large tsunamis
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DOI：
10.1016/j.quascirev.2022.107381
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发表时间：
2022-03
影响因子：
4
通讯作者：
T. Ishizawa;K. Goto;Y. Nishimura;Y. Miyairi;Chikako Sawada;Y. Yokoyama
中科院分区：
文献类型：
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作者：
T. Ishizawa;K. Goto;Y. Nishimura;Y. Miyairi;Chikako Sawada;Y. Yokoyama
估算古海啸的频率和规模是评估未来海啸风险的重要要求。然而，一些问题，如地面土壤侵蚀的后续海啸波和海啸沉积物的保存潜力，很难确定古海啸的历史准确地根据海啸沉积物。这项研究表明了高分辨率和连续测年的重要性，以构建古海啸的历史。这些方法足以确保使用校准的14 C年龄的地质记录的连续性。沿着三陆海岸，包括我们的研究区域（野田）在日本北方，即使已经进行了几个古海啸的研究，海啸沉积物和古海啸历史的年龄相关性还没有重建，因为大的变化，在海啸沉积物的估计年龄。我们在海岸和内陆地区分别采集了两个岩心样品，利用高分辨率和连续测年结果，证实了400-2700年前地质记录的连续性。由于历史记录记载了近400年来的海啸历史，我们可以构建一个连续的古海啸历史，从2700年前到现在，没有一个缺失的事件。由于我们的一个研究地点位于内陆，我们只能估计相当于1611年的Keicho和869年的Jogan海啸的大海啸的历史;小海啸无法检测到，因为这些地区没有被淹没。通过将这些结果与周边地区的古海啸历史相结合，我们重建了北方至三陆中部海岸广泛可比的海啸沉积物的古海啸历史。结果表明，古海啸的历史可以在网站之间的相关性。很明显，在过去400年里，海啸的间隔时间比沿着三陆海岸更长。虽然早期的研究往往估计海啸沉积物的年龄的基础上获得的结果，仅立即在海啸存款，我们的研究结果表明，高分辨率测年的重要性，以避免忽视任何海啸存款。顺序测年对于精确地关联广泛分布的海啸沉积物至关重要。
Estimating paleotsunami frequency and size is an important requirement for assessing future tsunami risks. However, several issues such as ground soil erosion by subsequent tsunami waves and the preservation potential of tsunami deposits make it difficult to ascertain the paleotsunami history accurately based solely on tsunami deposits. This study demonstrates the importance of high-resolution and sequential dating to construct paleotsunami history. Those methods are sufficient to secure continuity of the geological record using calibrated14C ages. Along the Sanriku coast including our study area (Noda) at northern Japan, even though several paleotsunami studies have been conducted, the age correlation of tsunami deposits and paleotsunami history has not been reconstructed well because of the large variation in the estimated ages of tsunami deposits. After taking two core samples near the shore and at inland sites, we used them to confirm the continuity of geological records for 400–2700 years ago based on high-resolution and sequential dating results. Because historical records have documented the tsunami history during the last 400 years, we can construct a continuous paleotsunami history from 2700 years ago to the present without a missing event. Because one of our study sites is located inland, we were able to estimate the histories only of large tsunamis equivalent to the 1611 CE Keicho and 869 CE Jogan tsunamis; small tsunamis cannot be detected because those areas were not inundated. By combining these 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. Results showed that the paleotsunami histories can be correlated among sites. It is readily apparent that the tsunami interval is greater during the past 400 years than it was earlier along the Sanriku coast. Whereas earlier studies often estimated the ages of tsunami deposits based on results obtained only immediately above and immediately beneath the tsunami deposit, our results demonstrate the importance of high-resolution dating to avoid overlooking any tsunami deposit. Sequential dating is crucially important to correlate widely distributed tsunami deposits accurately.