Various slow earthquakes (SEQs), including tremors, very low frequency events, and slow slip events (SSEs), occur along megathrust zones. In a shallow plate boundary region, although many SEQs have been observed along pan-Pacific subduction zones, SSEs with a duration on the order of a year or with a large slip have not yet been detected due to difficulty in offshore observation. We try to statistically detect transient seafloor crustal deformations from seafloor geodetic data obtained by the Global Navigation Satellite System-Acoustic (GNSS-A) combination technique, which enables monitoring the seafloor absolute position. Here, we report the first detection of signals probably caused by shallow large SSEs along the Nankai Trough and indicate the timings and approximate locations of probable SSEs. The results show the existence of large SSEs around the shallow side of strong coupling regions and indicate the spatiotemporal relationship with other SEQ activities expected in past studies.

中文翻译：

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GNSS-A探测到的南开海槽浅层缓慢滑移事件。

沿着特大推力区发生各种地震，包括震颤，极低频事件和慢滑事件（SSE）。在浅板边界区域，尽管在泛太平洋俯冲带上观测到许多SEQ，但由于海上观测困难，尚未检测到持续时间约为一年或滑动较大的SSE。我们尝试从通过全球导航卫星系统-声学（GNSS-A）组合技术获得的海底大地测量数据中，统计地检测瞬态海底地壳变形，从而能够监控海底绝对位置。在这里，我们报告了首次检测到可能是由南开海槽沿岸的浅大SSE引起的信号，并指出了可能的SSE的时间和大概位置。