Fig. 1

Down-dip segmentation and the spectrum of slip styles for the Nankai subduction zone. Horizontal projection of the rupture area of the 1854 \(M_L=8.4\), 1944 \(M_{\rm w}=8.1\) and 1946 \(M_{\rm w}=8.3\) earthquakes are outlined by orange contours, which approximately define the along-dip range of the seismogenic zone. Shallow low-frequency earthquakes and very-low-frequency earthquakes are located up-dip to the seismogenic zone. Deep slow-slip events are located down-dip extension of the seismogenic zone. Deep tremors are denoted by dark red dots clustered within a belt-like region down-dip to the deep slow-slip events. The 20-km-interval contours of the depth from 0 to 100 km (Hayes et al. 2018) and trench (thick black toothed lines) depict the geometry of the Philippine Sea slab that is subducting in the direction represented by the black arrow. P-P’ represents a reference profile for the two-dimensional model. The Median Tectonic Line (thick solid line) (Kawamura et al. 2003; Ito et al. 2009) and the landward limit of the accretionary prism (solid-dashed line) (Leggett et al. 1985; Kodaira et al. 2000; Takahashi et al. 2003) are the surface expression of the material boundaries shown in Fig. 11. The  spatial distribution of deep tremors is from Maeda and Obara (2009) and Obara et al. (2010); great earthquakes, slow-slip events and shallow  low-frequency earthquakes from Obara and Kato (2016)