The different effects of polished and post-slip roughnesses on fault stability

Abstract

Linking fault morphology to its mechanical properties in laboratory experiments may shed some light on analyzing the seismogenic potential of a natural fault. Many previous experiments suggested that increasing the roughness of a polished fault tends to stabilize the fault. Furthermore, the roughness of faults, both experimental and natural, spontaneously evolves during slip. Here, we investigate the effects of the polished roughness and the post-slip roughness on experimental fault stability. The experiments were conducted on a granodiorite fault under initial normal stresses of 5–6 MPa and total slip distances of 1.5–2.5 mm. The results reveal that the polished fault with a higher roughness exhibits stick-slip, while the post-slip fault with a lower roughness exhibits stable slip. Moreover, a decrease in the roughness of a post-slip fault tends to stabilize the fault. The monitored macroscopic loading data indicate that the critical slip distance is significantly greater in a post-slip fault than in a polished fault. These results imply that the critical slip distance of young, rough faults may evolve dramatically with slip, subsequently affecting the fault stability.