[M-IS32_30AM1] 地球掘削科学

[MIS32-02] IODP Expedition 348 南海付加体内部への超深部ライザー掘削概要

*廣瀬 丈洋¹、Tobin Harold²、Saffer Demian³、Toczko Sean¹、前田 玲奈¹、久保 雄介¹、金川 久一⁴、木村 学⁴、Expedition 348 乗船研究者 ⁵ (1.海洋研究開発機構、2.University of Wisconsin-Madison、3.Pennsylvania State University、4.千葉大学、5.IODP Expedition 348)

キーワード：IODP, NanTroSEIZE, Nankai Trough, accretionary prism

The Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) is a multi-disciplinary scientific project designed to investigate fault mechanics and seismogenesis along subduction megathrusts through seismic imaging, direct sampling, in situ measurements, and long-term monitoring in conjunction with laboratory and numerical modeling studies. As part of the NanTroSEIZE program, International Ocean Discovery Program (IODP) Expedition 348 started on 13 September 2013 and was completed on 29 January 2014. During Expedition 348, the drilling vessel Chikyu advanced the ultra-deep riser hole at Site C0002, located 80 km offshore from the Kii Peninsula, from a depth of 860 meters below sea floor (mbsf) to 3058.5 mbsf, the world record for the deepest scientific ocean drilling, and cased it for future access. The drilling operation successfully obtained data on formation physical properties from logging while drilling (LWD) tools, as well as from lithological analyses of cuttings and core from the interior of the active accretionary prism at the Nankai Trough. IODP Site C0002 is the currently only borehole to access the deep interior of an active convergent margin. We will present preliminary scientific results as well as key aspects of riser-drilling operations, including two sidetrack borehole drilling operations conducted in this never-before accessed tectonic environment.