Fig. 8

Input sediment thickness. The vertical thickness of sediment above SU3 and SU4 was estimated based on the interpretation of each seismic profile (color scale). Along each profile, the western edge of the mapped sediment thickness is the deformation front or the base of the landward slope. Thin black lines indicate the seismic lines, and the thick black lines indicate seismic profiles shown in Figs. 3, 4, 5. Magenta contours show the slip distribution during the Tohoku earthquake (Iinuma et al. 2012), same as Fig. 1. The yellow thick dashed rectangles are the areas where the chert (SU3) is apparently missing (from Fujie et al. 2020), same as Fig. 1. The background map is a gray-shaded bathymetric map with contours every 200 m. The thick black contour line denotes a water depth of 7000 m. Orange dashed lines with arrowheads indicate the three segments inferred in this study. Similar thickness map without sediment fills (only SU2) is shown as Additional file 1: Fig. S1