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  • October 30, 2023
[Frontier Letter] A review of shallow slow earthquakes along the Nankai Trough

In the Nankai subduction zone, the shallow (≤ 10 km) slow earthquakes actively occur in three specific spots: Hyuga-nada, off Cape Muroto, and southeast off the Kii Peninsula. Subducted sediments along the shallow plate boundary exhibit positive (a–b) values in most cases. This means that spontaneous nucleation is difficult at the shallow plate boundary along the Nankai Trough. The possible key factor for the occurrence of shallow slow earthquakes is fluid migration. Heterogeneous fluid distribution around the plate boundary fault was recognized by seismological studies. The episodic fluid migration around the shallow plate boundary could promote shallow slow earthquakes in regions with high-pore fluid pressure.