Estimation of mechanism of crustal deformation on the basis of high resolution analysis of incised valley fills near the source region of 2011 Tohoku-oki earthquake

2019 Fiscal Year Final Research Report

• Project/Area Number: 16H05903
• Research Category: Grant-in-Aid for Young Scientists (A)
• Allocation Type: Single-year Grants
• Research Field: Geography
• Research Institution: Chuo University (2017-2019); Tohoku University (2016)
• Principal Investigator: Niwa Yuichi 中央大学, 理工学部, 助教 (20705371)
• Project Period (FY): 2016-04-01 – 2020-03-31
• Keywords: 沖積層 / 放射性炭素年代 / 地殻変動 / 堆積相 / 東北地方太平洋沖地震

Outline of Final Research Achievements

This study estimated long-term (> 1000 years) crustal movements, which is necessary to clarify mechanism of megathrust earthquake cycles, on the basis of analyses of incised valley fills in alluvial plains along the Sanriku coast, near the source region of 2011 Tohoku-oki earthquake. Sedimentary analyses and radiocarbon dating showed distribution of shallow marine sediments in four alluvial plains along the Sanriku coast during the last ten thousand years. The distribution of shallow marine sediment and sediment stacking pattern indicate that millennial-scale crustal movements are characterized as subsidence along the central to southern Sanriku coast and relative uplift along the northern coas.

Free Research Field

地形学、第四紀学、自然地理学

Academic Significance and Societal Importance of the Research Achievements

従来、三陸海岸では限られた範囲でのみ認められる隆起海岸地形だけを根拠に、同海岸全域が長期的に隆起傾向にあるとみなされ、この隆起傾向を前提として超巨大地震繰り返しモデルが提案されてきた。本研究で明らかになった、三陸海岸の北部と南部の地殻変動傾向の違いは、従来の地震サイクルモデルの前提条件を見直す必要性を示すという点で、地震テクトニクス研究の発展やハザード評価に寄与する。