Tribochemical reaction and the mechanism of fault weakening at intermediate- to high-velocities

2014 Fiscal Year Final Research Report

• Project/Area Number: 24340104
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Partial Multi-year Fund
• Section: 一般
• Research Field: Solid earth and planetary physics
• Research Institution: Kyoto University
• Principal Investigator: TSUTSUMI Akito 京都大学, 理学(系)研究科(研究院), 助教 (90324607)
• Co-Investigator(Kenkyū-buntansha): SHIMOBAYASHI Norimasa 京都大学, 理学研究科, 教授 (70235688) ; MIYAKE Akira 京都大学, 理学研究科, 准教授 (10324609)
• Co-Investigator(Renkei-kenkyūsha): KAMEDA Jun 北海道大学, 理学研究科, 准教授 (40568713)
• Research Collaborator: NAMIKI Yuka 京都大学, 理学研究科
• Project Period (FY): 2012-04-01 – 2015-03-31
• Keywords: 断層摩擦 / 断層強度弱化 / 非晶質シリカ

Outline of Final Research Achievements

To get a better understanding of fault-weakening mechanism in silicic material, we have studied microstructure of the fault surface material in the samples derived from intermediate-velocity friction experiments on chert, and frictional properties of silicic sediments from the Cocos plate offshore the Osa Peninsula, Costa Rica. TEM observation reveals that the fault surfaces in chert after the experiments consist of several hundred-nm-thick amorphous silica layer. Wear rolls exist on the smooth fault surface. We find that rolls are also made of amorphous silica. Friction of the silicic sediments from the Costa Rica show velocity-weakening at velocities to 0.3 mm/s and neutral to velocity-strengthening behavior at velocities from 0.3 mm/s to 3 mm/s. At velocities higher than 30 mm/s, steady state friction values are as low as 0.1. These results imply the important influence of the generation and/or incorporation of amorphous silica on frictional behavior of silicic faults.

Free Research Field

構造地質学，実験岩石力学