The Nankai Trough subduction zone is a typical subduction system characterized by subduction of multiple geological units of the Philippine Sea Plate (the Kyushu-Palau Ridge, the Shikoku Basin, the Kinan Seamount Chain, and the Izu-Bonin Arc) beneath the Eurasian Plate in the southwest of Japan. This study presents a geophysical and geochemical analysis of the Nankai Trough subduction zone in order to determine the features and subduction effects of each geological unit. The results show that the Nankai Trough is characterized by low-gravity anomalies (−20 mGal to −40 mGal) and high heat flow (60–200 mW/m²) in the middle part and low heat flow (20–80 mW/m²) in the western and eastern parts. The crust of the subducting plate is 5–20 km thick. The mantle composition of the subducting plate is progressively depleted from west to east. Subduction of aseismic ridges (e.g., the Kyushu-Palau Ridge, the Kinan Seamount Chain, and the Zenisu Ridge) is a common process that leads to a series of subduction effects at the Nankai Trough. Firstly, aseismic ridge or seamount chain subduction may deform the overriding plate, resulting in irregular concave topography along the front edge of the accretionary wedge. Secondly, it may have served as a seismic barrier inhibiting rupture propagation in the 1944 M_w 8.1 and 1946 M_w 8.3 earthquakes. In addition, subduction of the Kyushu-Palau Ridge and hot and young Shikoku Basin lithosphere may induce slab melting, resulting in adakitic magmatism and the provision of ore-forming metals for the formation of porphyry copper and gold deposits in the overriding Japan Arc. Based on comparisons of their geophysical and geochemical characteristics, we suggest that, although the Izu-Bonin Arc has already collided with the Japan Arc, the Kyushu-Palau Ridge, which represents a remnant arc of the Izu-Bonin Arc, is still at the subduction stage characterized by a single-vergence system and a topographic boundary with the Japan Arc.

南海海槽俯冲带是典型的俯冲系统，其特征是俯冲欧亚板块下方的菲律宾海板块（九州-帕劳岭，四国盆地，济南海山链和伊豆-波宁弧）的多个地质单元被俯冲。日本西南部。本研究对南开海槽俯冲带进行了地球物理和地球化学分析，以确定每个地质单元的特征和俯冲作用。结果表明，南海海槽的特征是低重力异常（−20 mGal至−40 mGal）和中部高热流（60–200 mW / m ²），低热流（20–80 mW / m ²）²米）在西部和东部。俯冲板的地壳厚5–20 km。俯冲板块的地幔组成从西向东逐渐枯竭。地震脊（例如，九州-帕劳岭，济南海山链和泽尼苏岭）的俯冲是导致南开海槽一系列俯冲作用的常见过程。首先，抗震脊或海山链俯冲可能会使上覆板变形，导致沿增生楔形前缘的凹形地形不规则。其次，它可能已成为阻止1944 M _w 8.1和1946 M _w破裂扩展的地震屏障。8.3级地震。此外，九州-帕劳岭和四国盆地的热和年轻的岩石圈的俯冲作用可能引起板块融化，导致岩浆成岩作用，并为上覆日本弧中斑岩铜和金矿床的形成提供成矿金属。根据它们的地球物理和地球化学特征的比较，我们建议，尽管伊豆-波宁弧已经与日本弧相撞，但代表伊豆-波宁弧的残留弧的九州-帕劳岭仍在俯冲阶段，其特征是单一趋近系统和与日本弧的地形边界。