9:45 AM - 10:00 AM
[MIS20-03] Multiple event sand layers from the 12th to 17th centuries found in the northern Sendai Plain
Keywords:archaeological survey, Gamo-Okura ruin, tsunami deposit
Researches during the last 30 years have revealed that tsunami deposits from past large-scale interplate earthquakes are widely distributed on the Pacific coast of Tohoku. In the Sendai Plain, existence of event sand layers from the 1611 Keicho-Oshu, the 1454 Kyotoku and the 869 Jogan earthquakes has been known as historical tsunami deposits. Some researches reported another candidate tsunami deposit dated at a period between the Kyotoku and Jogan earthquakes, but it is not known whether or not the candidate can be correlated over the Sendai Plain and adjacent areas. Sediments of shallow subsurface have been disturbed and eroded by recent anthropogenic activities, making it often difficult to identify historical tsunami deposits.
Trench excavation, which is common in archaeological surveys, allows us for a detailed observation of sediments such as horizontal changes and continuity in layer thickness and structure. Being able to track sediment layers, even if they are disturbed, is a great advantage for tsunami deposit research. Recent archaeological survey at the Gamo-Okura ruin at the left bank of the Nanakita River in the northern Sendai Plain reported three event sand layers that can be correlated possibly with historical tsunamis in the 12th to 17th centuries. The ruin is located between the beach ridges II (formation completed before 1600 yr BP; Matsumoto, 1984) and III (formation started around 1300 cal BP; Ito, 2006), and was originally developed around 1673 AD as a water transportation base that connects Shiogama Port and Sendai Castle. In this presentation, the age and sedimentological characteristics of the event sand layers are examined to discuss their sources and relevance to the historical tsunamis or storm surges.
Trench excavation, which is common in archaeological surveys, allows us for a detailed observation of sediments such as horizontal changes and continuity in layer thickness and structure. Being able to track sediment layers, even if they are disturbed, is a great advantage for tsunami deposit research. Recent archaeological survey at the Gamo-Okura ruin at the left bank of the Nanakita River in the northern Sendai Plain reported three event sand layers that can be correlated possibly with historical tsunamis in the 12th to 17th centuries. The ruin is located between the beach ridges II (formation completed before 1600 yr BP; Matsumoto, 1984) and III (formation started around 1300 cal BP; Ito, 2006), and was originally developed around 1673 AD as a water transportation base that connects Shiogama Port and Sendai Castle. In this presentation, the age and sedimentological characteristics of the event sand layers are examined to discuss their sources and relevance to the historical tsunamis or storm surges.