Frictional healing of faults is a key mechanism controlling fault strength recovery, which enables the development of repeating earthquake cycles. Carbonate fault rocks are commonly characterized by shiny mirror-like surfaces, sometimes referred to as fault mirrors. Despite the prevalence of fault mirrors in both natural and experimental fault rocks, their frictional healing behavior has not yet been studied. We measured frictional healing rates of experimentally simulated carbonate fault mirrors and found them to be an order of magnitude lower than those of other carbonate fault rocks. Microstructurally, the fault zone of fault mirror specimens is characterized by densely packed sintered nanogouges. We infer that this tight nanograin structure hinders the chemical and physical processes that cause frictional healing. Fault mirrors showing extremely low frictional healing rates are likely to creep aseismically.
Bibliographical noteFunding Information:
The authors thank the editor Lucy Flesch, Jianye Chen, and two anonymous reviewers for their constructive comments that substantially improved the manuscript. This study was supported by the Nuclear Safety Research Program through the Korea Foundation of Nuclear Safety (KoFONS) using financial resources granted by the Nuclear Safety and Security Commission (NSSC) of the Republic of Korea (Grant no. 1705010) and partly by JSPS KAKENHI Grant number JP19K21907.
© 2021. The Authors.
- earthquake cycle
- fault mirror
- frictional healing
ASJC Scopus subject areas
- General Earth and Planetary Sciences