Japan Geoscience Union Meeting 2015

Presentation information


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

[S-SS29] Fault Rheology and Earthquake Dynamics

Sun. May 24, 2015 6:15 PM - 7:30 PM Convention Hall (2F)

Convener:*Wataru Tanikawa(Japan Agency for Marine-Earth Science and Technology, Kochi Instutute for Core Sample Research), Takeshi Iinuma(International Research Institute of Disaster Science, Tohoku University), Yuta Mitsui(Department of Geosciences, Graduate School of Science, Shizuoka University), Hideki Mukoyoshi(Department of Geoscience Interdisciplinary Graduate School of Science and Engineering, Shimane University)

6:15 PM - 7:30 PM

[SSS29-P15] Thermal and pressure effect on frictional property of smectite: application to the plate boundary earthquakes of Nankai

*Tomoyo MIZUTANI1, Ken-ichi HIRAUCHI1, Weiren LIN2, Michiyo SAWAI3 (1.Department of Geosciences, Graduate School of Science, Shizuoka University, 2.Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology, 3.Department of Earthsciences,Graduate School of Science,Hiroshima University)

Keywords:subduction thrust fault, decollement, aseismogenic zone, smectite, laboratory experiment, velocity dependence of friction

Along subduction thrust faults, the transformation from smectite to illite at 100-150℃ plays a key role to define the updip limit of the seismogenic zone. If this hypothesis is correct, it is required that smectite exhibits velocity strengthening behavior at in-situ effective normal stress (σeff) and ~100-150℃. Here we report results of friction experiments on gouges of pure Na-montmorillonite at σeff of 10-70 MPa, a pore fluid pressure of 10 MPa, at temperatures of 25-150℃, and sliding velocities of 0.03-3 μm/s, using an oil-medium triaxial testing machine. We found that the coefficient of friction (μ) ranges from 0.056 to 0.120. At temperatures of 20 to 60℃, μ systematically decreased with increasing σeff, while at 90-120℃, it increased with increasing σeff. With increasing σeff, the velocity dependence of friction (a-b) became negative at 25-90℃ and positive at 120℃. Therefore, we suggest that smectite friction promotes stable slip along the decollement at the shallow Nankai subduction zone.