Table 1.

Glossary of the terms for slow earthquakes used in this paper

Low-frequency tremor Weak seismic vibrations lasting from minutes to days with a predominant frequency of 1–10 Hz, which is lower than that of a regular microearthquake having a comparable amplitude to that of tremor. Tremor comprises swarm activities of LFE.

Low-frequency earthquake (LFE) A seismic event radiating a waveform with a predominant frequency of 1–10 Hz, which is lower than that of a regular earthquake having a comparable amplitude. LFEs are mainly distributed in volcanic areas and subducting plate interfaces. The LFEs along the subducting plate interface are considered an elementary process of low-frequency tremor.

Very-low-frequency earthquake (VLFE) A seismic event radiating a waveform with a predominant period of 10–100 s associated with very weak amplitudes of high-frequency components.

Slow slip event (SSE) A transient slip along the fault plane with no radiation of a seismic wave.

Long-term SSE SSEs with a duration ranging from months to years.

Short-term SSE SSEs with a duration ranging from days to weeks.

Episodic tremor and slip (ETS) Simultaneous occurrence of short-term SSEs, VLFEs, and tremor.