Fig. 2

Observed signals of the slow earthquake family. The slow earthquake family includes a low-frequency earthquakes (LFEs) (Shelly et al. 2007), b tectonic tremors (Ide et al. 2008), c very-low-frequency earthquakes (VLFEs) (Ide et al. 2008), d short-term slow slip events (SSEs) (Hirose and Obara 2010), and e long-term SSEs (Takagi et al. 2016). In d the daily count of concurrent tectonic tremors is presented (Hirose and Obara 2010). The dashed lines in d indicate calculated tilt changes due to the short-term SSE (Hirose and Obara 2010). All the above signals of the slow earthquake family were observed on the deeper plate interface (25–40 km depth) of the Nankai Trough. GNSS, global navigation satellite system