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<p>Large earthquakes and tsunamis are major hazards at subduction zones, where segmentation governs rupture extent and magnitude. However, the mechanisms that define segment boundaries remain unclear. In the eastern Nankai Trough, which is anticipated to host future megathrust earthquakes, the forearc is divided into the Tonankai and Tokai segments. Here we use newly acquired 3D seismic reflection data (2021–2022), to image structures across the segment boundary. High-resolution profiles reveal three seafloor topographic highs associated with active folding and thrusting in forearc sediments, the accretionary wedge, and along the plate interface. These features trend NNE–NE in Tonankai but ENE in Tokai, across an arcuate syntaxis. Collision of the Paleo-Zenisu Ridge, a remnant of the Izu–Bonin arc on the Philippine Sea Plate, appears to impose the syntaxis structure of the upper plate. Our results demonstrate that the forearc structural complexity exerts a primary control on margin segmentation and associated hazards.</p>

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Ridge collision sculpts forearc segmentation along the eastern Nankai Trough

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年5月5日

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  • Gaku Kimura,
  • Kazuya Shiraishi,
  • Yasuyuki Nakamura,
  • Gou Fujie,
  • Paul Caesar. M. Flores

摘要

Large earthquakes and tsunamis are major hazards at subduction zones, where segmentation governs rupture extent and magnitude. However, the mechanisms that define segment boundaries remain unclear. In the eastern Nankai Trough, which is anticipated to host future megathrust earthquakes, the forearc is divided into the Tonankai and Tokai segments. Here we use newly acquired 3D seismic reflection data (2021–2022), to image structures across the segment boundary. High-resolution profiles reveal three seafloor topographic highs associated with active folding and thrusting in forearc sediments, the accretionary wedge, and along the plate interface. These features trend NNE–NE in Tonankai but ENE in Tokai, across an arcuate syntaxis. Collision of the Paleo-Zenisu Ridge, a remnant of the Izu–Bonin arc on the Philippine Sea Plate, appears to impose the syntaxis structure of the upper plate. Our results demonstrate that the forearc structural complexity exerts a primary control on margin segmentation and associated hazards.