New fault model based on friction experiments across the deformation mechanism transitions

2020 Fiscal Year Final Research Report

• Project/Area Number: 16H04061
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Geology
• Research Institution: Chiba University
• Principal Investigator: Kanagawa Kyuichi 千葉大学, 大学院理学研究院, 教授 (40185898)
• Project Period (FY): 2016-04-01 – 2021-03-31
• Keywords: 摩擦実験 / 圧力溶解 / 地震性断層運動

Outline of Final Research Achievements

Triaxial friction experiments on opal gouge at a confining pressure of 150 MPa, a pore-water pressure of 50 MPa, temperatures of 25-200℃, and axial displacement rates of 0.1-10 μm/s revealed that frictional strength increases while frictional stability decreases with increasing temperature or decreasing displacement rate. In addition, stick-slips corresponding to seismic faulting occurred at temperatures ≧150℃. Microstructural observations also revealed coalescence of gouge particles by pressure solution in samples after experiments at temperatures ≧100℃.
These results suggest that increasing temperature or decreasing displacement rate promotes cohesion of fault zone materials to increase frictional strength, and thereby the transition from velocity strengthening to velocity weakening, i.e., the transition from stable aseismic faulting to unstable seismic faulting.

Free Research Field

構造地質学・岩石力学

Academic Significance and Societal Importance of the Research Achievements

圧力溶解による断層帯構成粒子の固結が地震性断層運動を促すという理論的仮説を実験的に検証し、沈み込み帯や内陸の非地震性から地震性への断層運動の遷移機構を明らかにしたことに、本研究の大きな学術的意義がある。また、地震に備える社会にとっても有益な情報を提供できたと考える。