Acknowledgments We gratefully acknowledge the assistance of the captain and his crew of R/V
Yokosuka, and operation team aboard the submersible SHINKAI 6500 during YK05-08 Leg. 2. Ms
Keiko Fujino provided much help with the heat flow measurement data. Professor Tadashi Sato
reviewed an early draft of the manuscript. Part of this study was supported by a Grant-in-Aid from
the Ministry of Education, Culture, Sports, Science and Technology of Japan (B-14740295).
Critical but constructive and thorough reviews of an earlier version of this paper for GEOLOGY
by Tim Byrne, Mike Underwood and John Wakabayashi helped us with our interpretations and
improved both the science and organization of work.
Ashi J, Taira A (1993) Thermal structure of the Nankai accretionary prism as inferred from the
distribution of gas hydrate BSRs. Geol Soc Am Spec Pap 273:137-149
Blenkinsop TG (1988) Definition of low-grade metamorphic zones using illite crystallinity.
J Metamorph Geol 6:623-636
Bray CJ, Karig DE (1985) Porosity of sediments in accretionary prisms and some implications for
dewatering processes. J Geophys Res 90:768-778
Cande SC, Kent DV (1995) Revised calibration of the geomagnetic polarity timescale for the Late
Cretaceous and Cenozoic. J Geophys Res 100:6093-6095
Dominguez S, Malavieille J, Lallemand SE (2000) Deformation of accretionary wedges in
response to seamount subduction: insights from sandbox experiments. Tectonics 19:182-196
Hyndman RD (2004) Controls on subduction thrust earthquakes: Downdip changes in composi-
tion and state. In: Karner GD, Taylor B, Driscoll NW, Kohlstedt DL (eds) Rheology and
deformation of the lithosphere at continental margins. Columbia University Press, New York,
Kinoshita M, Yamano M (1986) The heat flow anomaly in the Nankai trough area. In: Kagami H,
Karig DE, Coulbourn WT (eds) Initial reports of the deep sea drilling project 87. U.S.
Government Printing Office, Washington, DC, pp 737-743
Kodaira S, Nakanishi A, Park JO, Ito A, Tsuru T (2003) Cyclic ridge subduction at an interpolate
locked zone off central Japan. Geophys Res Lett 30:1139. doi:10.1029/2002GL016595
Kodaira S, Hidaka T, Kato A, Park JD, Iwasaki T, Kaneda Y (2004) High pore fluid pressure may
cause silent slip in the Nankai trough. Science 304:1295-1298
Kübler B (1968) Evaluation quantitative du metamorphism par la cristallinite de I'llite. Bull
Centre Rech Pau-SNPA 2:385-397
Kuramoto S, Okamura Y, Arai K, Murakami F (1999) High resolution multichannel seismic
survey in off Tokai area. Geol Surv Jpn Cruise Rep 24:33-50
Lallemand SE, Malavieille J, Calassou S (1992) Effects of oceanic ridge subduction on accretion-
ary wedges: experimental modeling and marine observation. Tectonics 11:1301-1313
Laughland MM, Underwood MB (1993) Vitrinite reflectance and estimates of paleotemperature
within the Upper Shikoku Group, Muroto Peninsula, Shikoku, Japan. Geol Soc Am Spec Pap
Le Pichon X, Lallemant S, Tokuyama H, Thoue F, Huchon P, Henry P (1996) Structure and evolu-
tion of the backstop in the eastern Nankai trough area (Japan): implications for the soontocome
Tokai earthquake. Isl Arc 5:440-454
Martini E (1971) Standard tertiary and quaternary calcareous nannoplankton zo-nation. In:
Farinacci A (ed) Proceedings of 2nd planktonic conference, Rome, 1970, Proceedings 2.
Tecnoscienza, Rome, pp 738-785
Mazzotti S, Lallemant SJ, Henry P, Le Pichon X, Tokuyama H, Takahashi N (2002) Intraplate
shortening and underthrusting of a large basement ridge in the eastern Nankai subduction zone.
Mar Geol 187:63-68
Middleton MF (1982) Tectonic history from virtinite reflectance. J Geophys Res 87:121-132