Overview of the 2011 Tohoku earthquake and localization of shallow slow earthquakes. Red circles were determined by NIED (2012). Coseismic slip is indicated by a color scale (Yagi and Fukahata 2011). The gray contours denote the slip areas for the recent major earthquakes at Miyagi-oki in 1978 (M 7.4) and 1936 (M 7.4), and at Fukushima-oki in 1938 (M 7.3, M 7.4, and M 7.5; Murotani 2003; Yamanaka and Kikuchi 2004). The gray broken lines denote the borders of Iwate, Miyagi, Fukushima, and Ibaraki prefectures. Gray and pink bold lines denote the trench axis and the down-dip limit of interplate earthquakes (Igarashi et al. 2001; Uchida et al. 2009). Rectangles with broken lines represent our suggestions based on the present study as described in the ‘Discussion’ section.