Japan Geoscience Union Meeting 2016

Presentation information

International Session (Poster)

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

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

Tue. May 24, 2016 5:15 PM - 6:30 PM Poster Hall (International Exhibition Hall HALL6)

Convener:*Kyuichi Kanagawa(Graduate School of Science, Chiba University), Demian Saffer(Department of Geosciences, The Pennsylvania State University, USA), Michael Strasser(University of Innsbruck), James Kirkpatrick(McGill University), Shuichi Kodaira(R&D Center for Earthquake and Tsunami Japan Agency for Marine-Earth Science and Technology), Ryota Hino(Graduate School of Science, Tohoku University), Yasuhiro Yamada(Japan Agency for Marine-Earth Science and Technology (JAMSTEC), R&D Center for Ocean Drilling Science (ODS)), Kohtaro Ujiie(Graduate School of Life and Environmental Sciences, University of Tsukuba), Yoshihiro Ito(Disaster Prevention Research Institute, Kyoto University)

5:15 PM - 6:30 PM

[SSS02-P14] Tectonic stress of the upper-plate crust above the Tonankai seismogenic zone

*Arito Sakaguchi1,2, Miki Inoue1, Yuya Komine1, Weiren Lin2, Osamu Tadai3, Kentaro Hatakeda3, Asuka Yamaguchi4 (1.Yamaguchi Univ., 2.JAMSTEC, 3.Marine Works Japan LTD., 4.AORI, Univ. of Tokyo)

Keywords:subduction earthquakes, IODP, physical property

The crustal physical property is necessary information to understand the seismogenic mechanism. Soft sediment changes to hard rock to be the seismogenic material during plate subduction. In this process, strength is the most developing property than the other of the porosity, bulk density, elastic wave velocity and etc. The sediment lithification depends on the stress due to strain hardening, and the strength of the sediment products us the stress condition in the plate subduction zone.
IODP Exp.338 took samples from 1000 mbsf to 2000 mbsf above the seismogenic zone of the Tonankai earthquake of 1944 (Mw=8.0) during Nankai Trough Seismogenic Zone Drilling Project (Moore et al., 2013). Because the riser-drilling, the cutting-sample were taken in all section differ from the core samples. These cutting-samples have the potential to make the strength profile of upper plate in the subduction zone. We develop new method to estimate the rock strength using the needle penetrator that applicable for small cuttings-sample. Since the needle penetration makes the Mode I crack, the obtained strength concerns with cohesion of the rock. This needle-penetration strength was compared with uniaxial compression strength using various strength samples of mortar and natural sandstones.
In the result, higher cohesive samples were obtained at deeper section at site C0002. The cohesion gradient increases suddenly at the boundary between the Kumano basin and the accretionary prism. The accretionary sediment may suffer tectonic stress, and high cohesion gradient can be explained by increasing tectonic stress with depth. In case of frictional sliding, shear stress within upper plate increases with depth above the asperity. The cohesion curve may show upper plate stress field in the seismogenic zone.