Time series analysis of depositional and erosional processes under tsunami

2019 Fiscal Year Final Research Report

• Project/Area Number: 16K17817
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Geology
• Research Institution: Ibaraki University
• Principal Investigator: Yamaguchi Naofumi 茨城大学, 広域水圏環境科学教育研究センター, 助教 (80634120)
• Project Period (FY): 2016-04-01 – 2020-03-31
• Keywords: 津波堆積物 / 水路実験 / 堆積過程

Outline of Final Research Achievements

We performed flume experiments to examine detailed time-series depositional and erosional processes, which is necessary for accurate identification of tsunami deposits and reconstruction of hydraulic conditions. In the present experiments, we focused on three possible factors which affect depositional and erosional processes: (1) terrestrial topography, (2) sediment grain size, and (3) water depth of the sediment source. The results of the experiments revealed time-series depositional and erosional processes related to the spatial distribution of the deposits under hydraulic conditions changed forcibly by a cliff, formation of spatial layer thickness distribution depending on sediment grain size, and water depth dependence of seafloor sediment entrainment.

Free Research Field

地質学

Academic Significance and Societal Importance of the Research Achievements

津波堆積物は，過去の津波の発生間隔やその規模といった沿岸地域の防災リスクを評価する上で重要となる情報を得るための貴重な手がかりとなるが，その形成過程は不明な点が多く，その識別や解釈は様々な仮定や憶測を含んでいるのが現状である．こうした現状に対して本研究課題によって，これまでの単純な最大流速や最大浸水深に結びつけた考え方だけでは説明できない津波堆積物の多様性の理解につながる成果が得られた．こうした理解は，過去の津波による堆積物を正確に識別し，その形成過程や水理条件を解釈するための新たな材料を提供するものである．