[S-CG45] Science of slow-to-fast earthquakes

[SCG45-P05] Frictional Weakening Behavior Characterized by Grain Comminution in the Sheared Halite Medium

*Chengrui Chang¹, Hiroyuki Noda², Yohei Hamada³, Gonghui Wang², Chao HUANG⁴, Tetsuo Yamaguchi¹ (1.the University of Tokyo, Graduate School of Agricultural and Life Sciences, 2.Kyoto University, Disaster Prevention Research Institute, 3.Japan Agency for Marine-Earth Science and Technology, Kochi Institute for Core Sample Research, 4.Kyoto University, Graduate School of Science)

Keywords:Grain comminution, Frictional weakening, Rock avalanche, Experimental fault zone, Microstructure

This study presents a novel experimental simulation of a growing fault zone in the granular medium of halite (NaCl). We conducted ring-shear tests and investigated the post-slip structure of the experimental fault zone by micro-CT and SEM. The sheared granular halite showed a two-regime mechanical behavior, i.e., a constant regime with a higher stable friction coefficient and a frictional weakening. The characteristic lengths of slip displacement for the constant and weakening regime were constrained and the normal-stress-dependent behavior was analyzed. We then combined mechanical data and micro-observations to propose that the system was characterized by drastic grain comminution and comminuted fine grains played as interstitial fluid. Finally, we established theoretical modeling to interpret that comminuted fines saturated and overflowed shear zone successively, which gave rise to the two-regime behavior.