Experimental study on generation and frictional properties of amorphous fault gouge layer

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K05575
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Geology
• Research Institution: Kyoto University
• Principal Investigator: Tsutsumi Akito 京都大学, 理学研究科, 助教 (90324607)
• Co-Investigator(Kenkyū-buntansha): 三宅 亮 京都大学, 理学研究科, 准教授 (10324609)
• Research Collaborator: NAMIKI yuka ; IIDA hirotaka ; ONOE yuko
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 岩石摩擦 / 石英岩 / 高速摩擦 / 速度弱化

Outline of Final Research Achievements

To study the effect of moisture on the fault zone process in siliceous material, we have performed friction experiments on a synthetic quartz sample under two different humidity conditions: in room humidity (relative humidity RH = 20 to 75%) and in dry (RH < 3%) conditions. In room humidity conditions, steady state friction shows velocity weakening at v ≧ 0.1 mm/s, which is consistent to the previous studies. We find that steady-state friction values measured at the dry condition are almost constant at f = 0.2 for slip velocities v ≧ 0.01 mm/s. Our results imply that the moisture-adsorption strengthening, which has been proposed to be an effective mechanism for time-dependent healing of high-velocity friction of gabbro (Mizoguchi et al. 2006) is an important underlying mechanism of the frictional weakening of quartz rocks observed in ambient humidity conditions.

Free Research Field

岩石力学、構造地質学

Academic Significance and Societal Importance of the Research Achievements

断層の地震時すべり挙動を理解するためには，断層がすべる際に、摩擦抵抗がどのように変化するのかを、様々な断層構成物質について明らかにする必要がある．近年，珪質な岩石の摩擦実験において，10 mm/s 程度の比較的ゆっくりとしたすべり速度条件で、摩擦係数が大きく減少する現象が見出され、そのメカニズムが国内外で議論されている。本研究では、人工水晶を用いた実験によって、断層物質表面の水分吸着の状態が摩擦の性質に大きく影響していることを明らかにした。