Multibeam (MB) and subbottom profile (SBP) data along the forearc slope off Miyagi, Japan, are combined to investigate structural-morphological and sedimentary structures along the forearc slope of the Japan Trench subduction zone. In addition to dip-oriented slope gullies, the MB data image a nearly dip-perpendicular slope trough bounded by a fault scarp landward of the trench-slope break. Seaward of the trench-slope break, the subbottom mostly contains normal faults that dip in opposite directions. The SBP data show not only unconformity and sliding surfaces, but also underfilled (forearc trough) and filled structures that may reflect the most recent forearc subsidence and basin filling. We propose these forearc trough and associated filling structures may indicate the earliest developments of modern isolated basins. Thus, a model of forearc basin development from slope gully to slope trough, isolated basins and forearc basin, transferred by active structures, could be proposed. Observed seafloor liquefaction in the SBP data may represent a near-surface seep structure of a plumbing system that enables hydrosphere-mantle fluid migration plausibly activated by earthquake cycles.

中文翻译：

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日本东北宫城外弧前斜坡的构造-形态和沉积特征：对弧前盆地和管道系统发展的影响

结合日本宫城外弧前斜坡的多波束 (MB) 和海底剖面 (SBP) 数据，研究日本海沟俯冲带前弧斜坡的构造-形态和沉积结构。除了倾斜取向的斜坡沟壑，MB 数据还成像了一个几乎倾角垂直的斜坡槽，其边界是向海沟斜坡断裂向陆的断层陡坡。海沟斜坡断裂的海面，底层主要包含向相反方向倾斜的正断层。SBP 数据不仅显示了不整合面和滑动面，还显示了未填充（弧前槽）和填充结构，它们可能反映了最近的弧前沉降和盆地填充。我们认为这些弧前槽和相关的充填结构可能表明现代孤立盆地的最早发展。因此，提出了弧前盆地从斜坡沟到斜坡槽、孤立盆地和弧前盆地、活动构造转移的发展模式。在 SBP 数据中观察到的海底液化可能代表了管道系统的近地表渗漏结构，该结构使水圈-地幔流体迁移可能被地震循环激活。