Thermochronometric investigations of the Southwest Japan Arc: toward elucidating the mechanism of a large earthquake along the Nankai Trough

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K14021
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 17040:Solid earth sciences-related
• Research Institution: Japan Atomic Energy Agency
• Principal Investigator: Fukuda Shoma 国立研究開発法人日本原子力研究開発機構, 核燃料・バックエンド研究開発部門 東濃地科学センター, 研究員 (70883479)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 熱年代学 / フィッション・トラック法 / (U-Th)/He法 / 山地形成過程 / 隆起・侵食 / 中国山地 / 四国山地

Outline of Final Research Achievements

In order to gain a further understanding of the mechanism of the Nankai Trough earthquake, we attempted to estimate the geological strain rate that contributes to deformation by applying low-temperature thermochronology to the southwest Japan Arc. (U-Th)/He and fission-track methods were applied along the two N-S traverses in the Chugoku and Shikoku Mountains. The following new findings were obtained: (1) No significant age difference between two traverses. (2) The spatial age distributions in the N-S direction revealed may correspond to uplift-subsidence-uplift zones. (3) Some of the obtained ages yielded approximately 10 Ma, suggesting that it may reflect tectonics after the Miocene.

Free Research Field

熱年代学，地質学

Academic Significance and Societal Importance of the Research Achievements

本研究は，西南日本弧において初めての体系的な熱年代学的研究であり，これまで未解明だったプレート間の相互作用による歪蓄積・解放モデルの理解に貢献可能な基盤データとして，中国山地・四国山地の隆起・削剥・冷却履歴を提供するものである．また，典型的な島弧として知られる東北日本弧との比較を通して，複雑な性格を持つ西南日本弧の特徴の抽出や形成過程の理解などの地質学的知見の取得はもちろん，防災などの社会的要請にも一定の貢献を与えるものと期待される．