2019 Ridgecrest Earthquake Rupture Reproduced by Low-Cost Discrete Fault Simulation

Abstract Dynamic simulations of earthquake sequences are expensive and time-consuming due to the inherent complexity of natural fault systems and the requirement of fine discretization in time and space for good numerical resolution. Simplified, low-cost earthquake simulations can provide significant benefits, as their shorter simulation times facilitate the exploration of a broader range of parameter space and enable trial-and-error tuning. To streamline the possibility of using such earthquake simulators for comparison with real-case examples, we conducted an earthquake simulation using the pixel-tracing technique to generate 3D nonplanar geometries of the Ridgecrest earthquake, assuming that the fault geometry is the only source of stress distribution. We conduct the simulations using two different grid dimensions: 200 and 500 m. The simulation times required to produce the Ridgecrest earthquake sequence are 20 min for the 200 m grid and just 1 min for the 500 m grid on a standard desktop computer (central processing unit: Intel 13900k). We show that, in some instances, the simulation yields a correct order of foreshock–mainshock sequence similar to the observations and predicts a distribution of slip in close agreement with the measurements. Notably, the slip magnitude at the end of the simulations is comparable for both grid dimensions, suggesting that the 1 min cost-efficient simulations still yield reliable results regarding potential rupture magnitude. In contrast, the timing and rupture sequence are highly sensitive to both physical inputs and numerical schemes, such as the stress field and the grid size. Overall, we conclude that our simplified, low-cost simulation method can be a valuable tool for investigating the mechanisms underlying specific earthquake rupture sequences and simulating potential earthquakes in fault systems with complex fault geometry.