Fig. 1

a Location of IODP Expedition 337 Site C0020A (the same site as Chikyu shakedown cruise CK06-06) (Modified after Inagaki et al. 2012). b A close-up map showing the distribution of the Ishikari-Sanriku-oki forearc basins, the Sanriku-oki subbasin, and the location of the Ministry of International Trade and Industry of Japan (MITI) Sanriku-oki well (Modified after Takano et al. 2012)