The Nankai Trough in Southwest Japan exhibits a wide spectrum of fault slip, with long-term and short-term slow-slip events, slow and fast earthquakes, all associated with different segments down the plate interface. Frictional and viscous properties vary depending on rock type, temperature, and pressure. However, what controls the down-dip segmentation of the Nankai subduction zone megathrust and how the different domains of the subduction zone interact during the seismic cycle remains unclear. Here, we model a representative cross-section of the Nankai subduction zone offshore Shikoku Island where the frictional behavior is dictated by the structure and composition of the overriding plate. The intersections of the megathrust with the accretionary prism, arc crust, metamorphic belt, and upper mantle down to the asthenosphere constitute important domain boundaries that shape the characteristics of the seismic cycle. The mechanical interactions between neighboring fault segments and the impact from the long-term viscoelastic flow strongly modulate the recurrence pattern of earthquakes and slow-slip events. Afterslip penetrates down-dip and up-dip into slow-slip regions, leading to accelerated slow-slip cycles at depth and long-lasting creep waves in the accretionary prism. The trench-ward migrating locking boundary near the bottom of the seismogenic zone progressively increases the size of long-term slow-slip events during the interseismic period. Fault dynamics is complex and potentially tsunami-genic in the accretionary region due to low friction, off-fault deformation, and coupling with the seismogenic zone.

中文翻译：

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南海海槽地震旋回的结构控制与系统级行为

日本西南部的南海海槽表现出广泛的断层滑动，具有长期和短期的慢滑动事件、慢地震和快地震，所有这些都与板块界面下方的不同段有关。摩擦和粘性特性因岩石类型、温度和压力而异。然而，是什么控制了南海俯冲带大逆冲断层的下倾分段以及俯冲带的不同域在地震周期中如何相互作用仍不清楚。在这里，我们模拟了四国岛近海南海俯冲带的代表性横截面，其中摩擦行为由上覆板块的结构和组成决定。巨逆冲断层与增生棱柱、弧壳、变质带、和上地幔一直到软流圈构成了重要的领域边界，这些边界塑造了地震周期的特征。相邻断层段之间的机械相互作用和长期粘弹性流的影响强烈地调节了地震和慢滑事件的复发模式。后滑通过下倾和上倾进入慢滑区域，导致深度处的慢滑循环加速和增生棱柱中的持久蠕变波。在震间期，靠近发震带底部的向海沟迁移的锁定边界逐渐增加了长期慢滑事件的规模。由于低摩擦、断层外变形以及与地震带的耦合，断层动力学是复杂的，并且可能在增生区引发海啸。