Fig. 1

A Bathymetric image along the Japan Trench. Two red circles indicate coring sites of NT13–19 PC08 and PC10. The orange point to the left of the coring sites is the hypothetical source of the turbidity currents for calculating PGA in this study. Line C transects the inset in C. Green inverted triangles indicate the sites of onland tsunami deposits (Sawai et al. 2012; Hirakawa 2012; Takada et al. 2016; Ishimura 2017). Yellow ellipses summarize the suggested rupture areas of historical earthquakes (M ~ 7.4 and larger) over the most recent 200 years (Koper et al. 2011; Toda 2016); 2: 1994 Sanriku-oki earthquake, 8: 1896 Sanriku earthquake. The rectangles with black solid lines are the suggested rupture areas of the 869 Jogan earthquake (Namegaya and Satake 2014). The rectangle with yellow solid lines is the suggested rupture area of the 1454 Kyotoku earthquake (Sawai et al. 2015). Numbers (1–8) of the rupture areas correspond to those in Additional file 7: Table S3. Irregular ellipses with yellow solid line indicate the area of coseismic slips, which were 4 m or greater when the 2011 earthquake occurred (Ozawa et al. 2011). Earthquakes other than those mentioned above (a–i) occurred in the following years: (a) 1856, (b) 1931, (c) 1901, (d) 1897, (e) 1936, (f) 1933, (g) and (h) 1938. The bathymetric chart (shaded-relief) is based on ETOPO1 (Amante and Eakins 2009). B Detailed bathymetry of the coring sites at NT13-19 PC08 and PC10. This inset is indicated by the green rectangle in A. Both coring sites PC08 and PC10 are in small basins in the MST. The bathymetric chart (shaded-relief) is based on a data-set provided by the Hydrographic and Oceanographic Department, Japan Coast Guard. C Migrated seismic profile of line C in A. Green areas show isolated basins above the onlap unconformities