Simplified structural model of the forearc region offshore of Miyagi prefecture. The model is based on the density structure and the seismic reflection images obtained along the black line shown in Figure1 (Miura et al.2005; Ito et al.2005). Numbers in parentheses indicate the densities in gram per cubic centimeter. UC, upper crust; LC, lower crust; MW, mantle wedge; OC, oceanic crust; SW, seawater. Numbers on the subducting plate denote dip angles between reference points (o to e). The location of the asperity of the 1978 Miyagi-oki earthquake, the epicenter of the 2011 Tohoku-oki earthquake (M9), and the trench axis are shown above the cross section. The ‘bending’ structures in segments d-e and b-c (Ito et al.2005) are interpreted as broken and unbroken seamounts, respectively (see text for details).