Stress state along the western Nankai Trough subduction zone inferred from b-values, long-term slow-slip events, and low-frequency earthquakes

Earth, Planets and Space

Table 1 The characteristics of b-values, LFEs, and SSEs activities in each region

Region	LFE activity	SSE activity—size	b-value
Kii Peninsula	〇	×	High (b ~ 1.2)
Kii Channel	×	〇 (but, not during the analysis period)—Medium (M_w 6.6–6.7)	Moderate (b ~ 1.0)
Central Shikoku	〇	〇 Very small (M_w 6.0–6.3)	Low (b ~ 0.6)
Western Shikoku	〇	〇 Small (M_w 6.0–6.3)	High (b ~ 1.2)
Bungo Channel	〇	〇 Large (M_w 7.0–7.1)	High (b ~ 1.2)
Northern Miyazaki	×	〇 (but, not during the analysis period)—medium (M_w ~ 6.5)	Moderate (b ~ 1.0)
Hyuga-nada	×	〇 Medium (M_w ~ 6.7)	Moderate to low (b ~ 0.8)

The magnitude size of the SSEs is based on the following studies: (1) Kii Channel (Kobayashi 2014; Geospatial Information Authority of Japan 2016); (2) west to central Shikoku (Takagi et al. 2016); (3) Bungo Channel (Ozawa et al. 2013; Ozawa 2017); (4) northern Miyazaki (Ozawa et al. 2001); and (5) Hyuga-nada regions (Yarai and Ozawa 2013)