Numerical Insights Into the Effect of Normal Stress on Stick‐Slip Characteristics in Faults With Granular Gouge

Abstract Granular fault gouge forms through the long‐term wear, fragmentation, and fracturing of mature faults. Studying the influence of normal stress on the stick‐slip behavior of fault gouges is essential for understanding the frictional mechanisms and their role behind geological hazards such as landslide initiation. In this study, we constructed a fault system with granular gouge to investigate the effect of normal stress on the characteristics of stick‐slip dynamics using the discrete element method. The results show that the stick‐slip dynamics are strongly affected by normal stress. As normal stress increases, the coordination number of particles increases while the slipping contact ratio decreases. Higher normal stress increases interparticle contact forces, enhancing frictional coupling and promoting stronger interlocking. This leads to more heterogeneous internal force distributions within the gouge, resulting in greater fluctuations in stick‐slip friction and strain energy. These changes are accompanied by the development of stronger and longer force chains, intensified pseudo‐acoustic emission signals, greater kinetic energy variations, and larger particle displacements. Statistical analysis of slip event sizes reveals that the average recurrence time and its variability decrease with increasing normal stress, while the number of slip and microslip events increases, with a more pronounced increase observed in microslip occurrences. These findings enhance our understanding of the influence of normal stress on stick‐slip dynamics and provide new insights into the mechanisms driving microslip events in fault systems.