Stress drop sequences in the simplest pressure-sensitive ideal elasto-plastic media: implications for earthquake cycles

Abstract. This study explores stress drops and earthquake sequences in the simplest pressure-sensitive elasto-plastic media using two-dimensional simulations, emphasizing the critical role of temporal and spatial resolution in accurately capturing stress evolution and strain localization during seismic cycles. Our analysis reveals that stress drops – triggered by plastic deformation once local stresses reach the yield criterion – resemble fault rupture mechanics, where accumulated strain energy is suddenly released, simulating earthquake-like behavior. Finer temporal and spatial discretization leads to sharper stress drops and lower minimum stress values, for simulations that have not converged yet. Displacement accumulates gradually during interseismic periods and intensifies during major stress drops, capturing key features of natural earthquake cycles. The histogram of stress drop amplitudes exhibits a non-Gaussian distribution. This “solid turbulence” behavior suggests that stress is redistributed across spatial and temporal scales, with implications for understanding the variability of stress drop magnitudes. Our results demonstrate that high-resolution elasto-plastic models can reproduce essential features of earthquake nucleation and stress drop behavior without relying on complex friction laws or velocity-dependent weakening mechanisms. These findings emphasize the necessity of incorporating plasticity into fault slip models to better understand the mechanisms of fault weakening and rupture. Furthermore, our work suggests that extending these models to three-dimensional fault systems and incorporating material heterogeneity and fluid interactions could offer deeper insights into seismic hazard assessment and earthquake mechanics.