Earthquake Cycle Simulations on Complex Three-Dimensional Fault Geometries Using Curved Boundary Elements

Yudong Sun, Andrew M. Bradley, & Paul Segall

Submitted August 30, 2026, SCEC Contribution #15342, 2026 SCEC Annual Meeting Poster #028

Earthquake cycle simulations have traditionally represented complex three-dimensional faults using tessellations of planar boundary elements, which introduce inaccuracies in stress calculations. We present a curved boundary element framework for simulating quasi-dynamic earthquake cycles on nonplanar faults while maintaining the accuracy and efficiency of boundary integral methods. This method integrates the point Green's function over curved elements using the circular-sector finite-part method, achieving second-order accuracy with second-order dislocation reconstruction. We benchmark the numerical stress calculations against an analytical solution for a nonplanar fault under the small-slope approximation and validate the earthquake cycle simulations using the SCEC SEAS benchmark problems. Interestingly, despite the substantially improved stress accuracy, in some cases, the simulated earthquake cycles remain qualitatively similar to those obtained with planar elements, suggesting that local stress errors introduced by discretization have little influence when the mesh size is much smaller than the cohesive zone. Using this framework, we investigate how three-dimensional fault geometry influences earthquake cycle behavior. We find that both the fault curvature in the slip direction and the surface torsion, which describes variations in fault slope perpendicular to the slip direction, perturb the normal stress on the fault. The resulting heterogeneous normal stress field strongly influences earthquake nucleation, propagation, and termination, leading to significant changes in earthquake cycle behavior. Our results demonstrate the critical role of three-dimensional fault geometry in earthquake cycles and establish a computational framework for accurate long-term simulations on nonplanar faults.

Key Words
fault roughness, numerical method

Citation
Sun, Y., Bradley, A. M., & Segall, P. (2026, 08). Earthquake Cycle Simulations on Complex Three-Dimensional Fault Geometries Using Curved Boundary Elements. Poster Presentation at 2026 SCEC Annual Meeting.

Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)