Fig. 1

(a) Map around the source area of the Tohoku-Oki earthquake. The focal mechanism at the red star indicates the best-fit solution obtained from our waveform inversion of the Tohoku-Oki earthquake. Solid black triangles show the locations of stations used in the inversion. Small black dots denote node points for the spatial grid search, and contour lines represent the residuals at a depth of 30 km. The focal mechanisms at the blue and cyan stars are those determined by the Global CMT project and U.S. Geological Survey. Station codes with underlines are the stations used in the corner frequency analysis. (b) Map showing bathymetry along the Japan Trench and topography of northeast Japan. The red circle represents the source area of the Tohoku-Oki earthquake estimated by this study. The yellow arrow indicates the convergence rate vector of the Pacific Plate with respect to the North American Plate. Focal mechanisms represent aftershocks with thrust type mechanisms that occurred within the subducted plate (Asano et al., 2011).