FASTDASH: An Implementation of 3D Earthquake Cycle Simulation on Complex Fault Systems Using the Boundary Element Method Accelerated by H-matrices

TL;DR

This paper introduces FASTDASH, a 3D earthquake cycle simulation method for complex fault systems using boundary element and hierarchical matrices, enabling efficient modeling of realistic fault geometries and seismic behavior.

Contribution

The paper presents a novel 3D slip dynamics model that handles complex fault geometries and accelerates computations with H-matrices, overcoming previous algorithmic limitations.

Findings

Validated with analytical solutions and benchmarks.

Successfully modeled the 2023 Kahramanmaras earthquake fault system.

Generated slip sequences matching real earthquake observations.

Abstract

Fault systems have geometrically complex structures in nature, such as stepovers, bends, branches, and roughness. Many geological and geophysical studies have shown that the geometrical complexity of fault systems in nature decisively influences the initiation, arrest, and recurrence of seismic and aseismic events. However, a vast majority of models of slip dynamics are conducted on planar faults due to algorithmic limitations. We develop a 3D quasi-dynamic slip dynamics model to overcome this restriction. The calculation of the elastic response due to slip is a matrix-vector multiplication in boundary element method, which can be accelerated by using hierarchical matrices. The computational complexity is reduced from the order of O(N^2) to O(N log N), where N is the number of degree of freedoms used. We validate our code with a static crack analytical solution and the SEAS benchmark/validation exercise from Southern California Earthquake Center. We further employ this method on a realistic fault system with complex geometry that was reactivated during the 2023 Kahramanmaras - Turkiye doublet earthquakes, generating slip sequences that closely match real observations.