Shiraishi Kazuya, Nakamura Yasuyuki, Arai Ryuta, No Tetsuo, Kaiho Yuka, Miura Ryo, Nakanishi Ayako, Miura Seiichi, Fujie Gou, Kodaira Shuichi
Research Institute for Marine Geodynamics, Japan Agency for Marine- Earth Science and Technology (JAMSTEC), Yokohama, Japan.
Sci Rep. 2025 Jul 30;15(1):25530. doi: 10.1038/s41598-025-08846-x.
The heterogeneous distributions of large and slow earthquakes in subduction zones are caused by multiple uncertain conditions in the source regions, and the basement topography is considered one of the major controlling factors. We revealed the topography of the subducting basement along the entire Nankai Trough on the basis of seismic reflection profiles compiled from 1997 to 2024. We interpreted the reflection profiles in the time domain to ensure consistency among multiple-generation datasets. The new surface model captured the detailed topography on a scale of several kilometers, over 730 km long and 150 km wide, and down to depths of 15-20 km. The basement topography is characterized by past tectonic activity and is divided into three domains, which affect the present heterogeneity in geological structures and physical properties along the Nankai Trough. While the three domains correspond to megathrust seismogenic zones along the Nankai Trough, the lack of correspondence between the significant topographic relief and the slow earthquake distribution in some areas suggests the need for additional factors controlling spatiotemporal variations in seismicity.
俯冲带中大地震和慢地震的非均匀分布是由震源区的多种不确定条件造成的，基底地形被认为是主要控制因素之一。我们基于1997年至2024年汇编的地震反射剖面，揭示了南海海槽俯冲基底的地形。我们在时域中解释反射剖面，以确保多代数据集之间的一致性。新的地表模型捕捉到了详细的地形，其规模为几公里，长730多公里，宽150公里，深度达15 - 20公里。基底地形具有过去构造活动的特征，分为三个区域，这三个区域影响了南海海槽沿线地质结构和物理性质的当前非均匀性。虽然这三个区域对应于南海海槽沿线的巨震源区，但在某些区域，显著的地形起伏与慢地震分布之间缺乏对应关系，这表明需要其他因素来控制地震活动的时空变化。
