(a) The location of the Oshika array (solid triangle) and the epicenter of the Tohoku-Oki earthquake (solid star). The gray star is the epicenter of the 9 March, 2011, earthquake. The Japan Trench is shown by a solid curve. The two rectangles drawn with thick solid lines are two subfaults proposed from geodetic observations by GSI. The three regions enclosed by thin dotted curves are the candidate source regions of the expected Miyagi-Ken-Oki earthquake by HERP. Back-azimuths from the Oshika array are shown by radial lines. A linear fault with a strike of 202° is assumed and shown by a thick line, beside which distances are written. The reference point from which the distance is measured is located at 38.145°N and 142.544°E. (b) Configuration of the Oshika array. This map is overwritten on the enlarged 1:25,000-scale topographical map of ‘Kinkasan’ issued by GSI. There are seven stations constituting the array. A number is attached to each station as shown on the map. Stations with solid triangles were operational at the time of the Tohoku-Oki earthquake.