Japan Geoscience Union Meeting 2015

Presentation information


Symbol S (Solid Earth Sciences) » S-CG Complex & General

[S-CG57] Structure, evolution and dynamics of mobile belts

Wed. May 27, 2015 2:15 PM - 4:00 PM A06 (APA HOTEL&RESORT TOKYO BAY MAKUHARI)

Convener:*Toru Takeshita(Department of Natural History Sciences, Graduate School of Science, Hokkaido University), Hiroshi Sato(Earthquake Prediction Research Center, Earthquake Research Institute, The University of Tokyo), Koichiro Obana(Research and Development Center for Earthquake and Tsunami, Japan Agency for Marine-Earth Science and Technology), Takuya NISHIMURA(Disaster Prevention Research Institute, Kyoto University), Yukitoshi Fukahata(Disaster Prevention Research Institute, Kyoto University), Aitaro Kato(Graduate School of Environmental Studies, Nagoya University), Jun Muto(Department of Earth Sciences, Tohoku University), Katsushi Sato(Division of Earth and Planetary Sciences, Graduate School of Science, Kyoto University), Shuichi Kodaira(Institute for Research on Earth Evolution Japan Agency for Marine-Earth Science and Technology), Takeshi Sagiya(Disaster Mitigation Research Center, Nagoya University), Tatsuya Ishiyama(Earthquake Research Institute, University of Tokyo), Makoto MATSUBARA(National Research Institute for Earth Science and Disaster Prevention), Yasutaka Ikeda(Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo), Chair:Eiji Kurashimo(Earthquake Research Institute, the University of Tokyo)

3:57 PM - 4:00 PM

[SCG57-P16] Changes in seismic velocity and electrical conductivity in a brine-saturated granite under uni-axial compression

3-min talk in an oral session

*Misaki MORIMOTO1, Tohru WATANABE1 (1.Department of Earth Sciences, University of Toyama)

Keywords:seismic velocity, electrical conductivity, anisotropy, fluid, compression, stress

Geophysical observations have shown that fluids exist pervasively within the crust. Fluids are mainly situated at intra-grain cracks and open grain boundaries. Since the opening of cracks strongly depends on the stress state, bulk properties such as seismic velocity and electrical conductivity, which are strongly affected by fluid-filled cracks, should be anisotropic under a stress state. In order to understand the anisotropy in velocity and conductivity under stress, we have been constructing an experimental system for studying the anisotropy in elastic wave velocity and electrical conductivity in a brine-saturated granitic rock under uni-axial stress.
The loading system is composed of a hand press (Maximum load: 20 kN), a load cell and stainless steel end-pieces, which contains ultrasonic transducers for velocity measurements in the axial direction. A fine grained (100-500 ?m) biotite granite (Aji, Kagawa Pref., Japan) was selected as a rock sample for its small grain size and textural uniformity. A cylindrical sample (D=26 mm, L=30 mm), to the cylindrical surface of which ultrasonic transducers are mounted for velocity measurements in the radial direction, is assembled with end-pieces, and then loaded. One compressional wave velocity and two shear wave velocities can be measured in the axial and two radial directions. Electrical impedance can also be measured in the axial and radial directions.
Preliminary runs on a dry rock sample have showed that velocities in the axial direction increased significantly with the axial compression. No significant change was observed in velocities propagating in the radial directions. These observations can be explained by the closure of cracks perpendicular or subperpendicular to the compression axis. Experiments on wet samples will also be reported in this poster.