Japan Geoscience Union Meeting 2015

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International Session (Poster)

Symbol S (Solid Earth Sciences) » S-SS Seismology

[S-SS02] Frontier studies on subduction zone megathrust earthquakes and tsunamis

Mon. May 25, 2015 6:15 PM - 7:30 PM Convention Hall (2F)

Convener:*Kyuichi Kanagawa(Graduate School of Science, Chiba University), Demian Saffer(Dept. of Geosciences, The Pennsylvania State University, USA), Michael Strasser(Geological Institute, Seiss Federal Insitute of Technology ETH Zurich), Yasuhiro Yamada(Depertment of Urban Management Engineering, Kyoto University), Shuichi Kodaira(Institute for Research on Earth Evolution Japan Agency for Marine-Earth Science and Technology), Ryota Hino(International Research Institute of Disaster Science, Tohoku University), Kohtaro Ujiie(Graduate School of Life and Environmental Sciences, University of Tsukuba), Yoshihiro Ito(Disaster Prevention Research Institute, Kyoto University)

6:15 PM - 7:30 PM

[SSS02-P06] Clay minerals in the Nankai Trough accretionary sediments as a function of depth

*Koki HOSHINO1, Kyuichi KANAGAWA1 (1.Department of Earth Sciences, Chiba University)

Keywords:clay minerals, accretionary sediments, Nankai Trough

We investigated how clay minerals in the Nankai Trough accretionary sediments change in content with depth from ≈950 mbsf (meters below seafloor) to ≈3030 mbsf at IODP Site C0002 off Kii Peninsula. Quantitative XRD analyses reveal that the content of smectite relative to total clay minerals decreases with depth from ≈76 wt% to ≈40 wt %, while those of illite and kaolinite increase with depth from ≈10 wt% to ≈30 wt%. Borehole temperature measurement at this Site revealed the temperature at 900 mbsf to be 38 ℃, while the temperature at ≈3000 mbsf has been estimated to be ≈100 ℃ based on the temperature and heat flow data at ≈900 mbsf and logging-while-drilling bit resistivity data. Thus the observed changes in contents of clay minerals likely reflect a temperature increase with depth.