Understanding of protothrust zone at trench axis around the Nankai Trough

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K17824
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Geology
• Research Institution: Japan Agency for Marine-Earth Science and Technology
• Principal Investigator: YAMASHITA Mikiya 国立研究開発法人海洋研究開発機構, 地震津波海域観測研究開発センター, 研究員 (00415978)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: プロトスラスト帯 / 南海トラフ / 海底地形

Outline of Final Research Achievements

The distribution of protothrust zone is imaged by using high resolution multi-channel seismic reflection data acquired around trench axis in Nankai Trough. In order to extract the micro-scale deformation of the protothrust zone at the seafloor, a new developed elaborate visualization “Red Relief Image Map” which is new three-dimensional presentation technique is applied to high-quality bathymetric data by the multi-beam echo sounder. Not only the visible deformation of accretionary prism, but also some arrangements of incipient thrust beneath the seafloor within protothrust zone corresponding to seismic reflection profiles along the trench axis are sharply recognized by the Red Relief Image Map method. Our findings can provide information about possible location of future frontal thrust within the protothrust zone.

Free Research Field

固体地球物理学

Academic Significance and Societal Importance of the Research Achievements

南海トラフではこれまで巨大地震が繰り返し発生しており，地震動や津波を予測するために様々な数値シミュレーションが行われてきている．しかしながら巨大な震源域の南端を規定する構造はなく，トラフ底の地形のみから決定されてきた．本研究ではプレート境界断層先端部の挙動を地下構造および高精度の海底地形から評価することで，破壊域の根拠となる地下構造を明らかにした．今後はトラフ全域について同様の研究を進めることでより正確な予測につながり，地震・津波防災に寄与することが期待できる．