Fig. 1

Co-seismic slip of the 2011 Tohoku earthquake and previous M7-class earthquakes around the source region (after Ikuta et al. 2012). a Co-seismic slip distribution of the 2011 Tohoku earthquake (blue color scale); the area with slip greater than 10 m is enclosed by a white line. The two stars show the locations of the main shock and the largest after-shock (March 11, 2011). The asperity distribution for M7-class earthquakes occurring in the past 80 years is shown by colored contours (after Murotani et al. 2004; Yamanaka and Kikuchi 2004; Yamanaka (NGY Seismology Notebook, http://www.seis.nagoya-u.ac.jp/sanchu/Seismo_Note, last updated November 25, 2015)). The contour for each asperity encloses the area in which the slip is greater than half of the maximum slip. b Cumulative seismic slip distribution along the trench for the earthquakes shown in a. The total length of each arrow represents the maximum slip of the event, and the length of the body of each arrow represents the average slip. Modified after Figure 12b in Yamanaka and Kikuchi (2004), with the addition of the following: data for the 1952 and 2003 earthquakes off Tokachi in the northern part of the trench are from Yamanaka and Kikuchi (2003); data for earthquakes in 1938 and 1982 in the R4 region are from Murotani et al. (2004) and Mochizuki et al. (2008), respectively; and data for recent earthquakes are from Yamanaka, NGY Seismology Notebook, http://www.seis.nagoya-u.ac.jp/sanchu/Seismo_Note, last updated November 25, 2015. Slip on spatially overlapping asperities is accumulated. Vertical dotted line shows the total expected tectonic slip over 80 years