Long-term aseismic sliding processes preceding unstable slip

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K04032
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 17040:Solid earth sciences-related
• Research Institution: The University of Tokyo
• Principal Investigator: Kato Naoyuki 東京大学, 地震研究所, 教授 (60224523)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 地震 / 非地震性すべり / 摩擦 / 地震サイクル

Outline of Final Research Achievements

I investigated propagation of aseismic sliding preceding unstable slip, by conducting numerical simulations of earthquake cycles with a rate- and state-dependent friction law. Aseismic sliding within the shallow velocity-weakening plate interface is generated by stress concentration due to deep stable sliding within the velocity-strengthening region. The propagation velocity of aseismic sliding, which propagates upward along the plate interface, is inversely proportional to the applied effective normal stress and independent of the characteristic slip distance of the friction law. This result is theoretically consistent with a model on the basis of fracture mechanics. Stresses and frictional property of plate interfaces may be estimated from observational data about propagation of aseismic sliding.

Free Research Field

地震学

Academic Significance and Societal Importance of the Research Achievements

速度・状態依存摩擦則を利用したモデルにより，プレート境界の多様なすべり現象が説明可能となり，地震サイクルの数値モデルが実現している，しかしながら，プレート境界の応力や摩擦パラメタについての情報は乏しい．本研究では，観測データから，プレート境界の応力や摩擦パラメタを推定できる可能性を示し，より適切な地震サイクルモデルの実現に寄与すると考えられる．また，地震発生に先行する非地震性すべりの特徴を明らかにしたことから，地震に至る過程の詳細が解明され，地震発生への切迫度が評価できる可能性が示された．