Estimation of stress state and detailed structure of the shallow plate boundary based on 3D active-source seismic data

2020 Fiscal Year Final Research Report

• Project/Area Number: 18K13641
• 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 Agency for Marine-Earth Science and Technology
• Principal Investigator: Arai Ryuta 国立研究開発法人海洋研究開発機構, 海域地震火山部門(地震発生帯研究センター), 副主任研究員 (20738752)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: 3D地震探査 / プレート沈み込み帯 / P波速度異方性 / 津波地震

Outline of Final Research Achievements

To reveal the physical and frictional properties of the shallow part of the plate boundary, I constructed a three-dimensional (3D) anisotropic P-wave velocity (Vp) structure model in the northern Hikurangi margin, New Zealand, by applying a traveltime tomography analysis to 3D seismic refraction data. The Vp model shows that significant anisotropic features occur in the vicinity of active branching faults in the accretionary wedge and the plate boundary. The fast axes of Vp are consistent with the direction of the plate convergence and thus reflect the compressional stress regime caused by the subduction. On the other hand, it rotates to the trench-parallel direction on the landward side of the forearc basin, which suggests that the coupling condition at the plate boundary and fault structures in the overriding plate may change at this location.

Free Research Field

構造地震学

Academic Significance and Societal Importance of the Research Achievements

本研究により、プレート境界浅部の地震波速度異方性がプレート境界の応力状態やすべり様式、断層構造と密接に関係することがわかった。その学術的な意義が認められ、本研究の成果を出版した国際学術論文はEditors' Highlightsに選出され、高い評価を受けた。本研究と同様のデータ解析を日本周辺を含む他の沈み込み帯に適用することで、プレート境界浅部の実態とそこで発生する地震活動に関する理解がさらに進むと考えられる。