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

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

*Chengrui Chang¹、野田 博之²、濱田 洋平³、王 功輝²、黄 超⁴、山口 哲生¹ (1.東京大学, 大学院農学生命科学研究科、2.京都大学, 防災研究所、3.海洋研究開発機構, 超先鋭研究開発部門、4.京都大学, 大学院理学研究科)

キーワード：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.