Reconstruction of Quaternary crustal uplifting history of island arcs by inversion of river longitudinal profiles

2020 Fiscal Year Final Research Report

• Project/Area Number: 18K18786
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 17:Earth and planetary science and related fields
• Research Institution: Kyoto University
• Principal Investigator: Naruse Hajime 京都大学, 理学研究科, 准教授 (40362438)
• Co-Investigator(Kenkyū-buntansha): 堤 昭人 京都大学, 理学研究科, 准教授 (90324607)
• Project Period (FY): 2018-06-29 – 2021-03-31
• Keywords: 逆解析 / テクトニクス / 堆積学 / 地形学 / モーフォダイナミクス

Outline of Final Research Achievements

In this study, we developed an inverse analysis method to reconstruct the tectonics of active continental margin such as the Japanese Islands from the longitudinal profiles of rivers. The method is based on the MCMC method, so that the uncertainty of the results can be evaluated. The developed method is applied to river systems in the Kii Peninsula, Shikoku and Tohoku regions, and the results for the past 120,000 years are in good agreement with the existing method. Futhremore, tectonic histories of past 600,000 - 800,000 years were estimated, which was difficult for existing methods. This study suggests that the inversion method of the river longitudinal profiles is suitable for reconstructing the Quaternary tectonics of island arcs.

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Free Research Field

堆積学

Academic Significance and Societal Importance of the Research Achievements

これまで困難であった第四紀島弧テクトニクスの面的かつ連続的な復元が本研究で開発した手法により可能となった．既存の地形学的手法では，隆起速度が復元できるのは段丘が存在する地域に限定されたり，熱年代学的手法では適用可能な岩相に制約があった．島弧の地殻隆起速度の履歴を知ることは，活動的縁辺域のプレートテクトニクスを理解することに役立つだけではなく，二酸化炭素回収・貯留に関する長期評価や，核廃棄物の地層処分にとっても基盤的な情報を与えるだろう．