Figure 1

(a) Tectonic setting of Japan and location of the study site. The rupture of the 2011 earthquake is from Ozawa et al. (2011)⁶³. (b) Map of the Kiritappu marsh showing distributions of tsunami deposits formed in the seventeenth century and thirteenth-fourteenth century^3,64, historical tsunami inundation area^3,5, simulated inundation area from a multi-segment interplate earthquake tsunami^3,5,7, and Pleistocene marine terraces⁶⁵. Inter-ridge ponds defined by beach ridges trend parallel to the present shoreline. (c) Cartoon showing the formation of a scour pond. The foredune and berm are reamed out perpendicular to the contemporary shoreline by inflow and outflow currents. The resulting scour pond then becomes isolated as the sandy beach is rebuilt with drift sand due to daily tides. The fan deposit created by inflow currents remains as a tsunami deposit upon the foredune and marsh. Generic Mapping Tools⁶⁶ was partly used to create Fig. 1a. Figure 1b was modified from Sawai¹.