BIEM_CH: An Efficient Algorithm for Dynamic Rupture Simulation of Complex Fault Systems with Unstructured Meshes and Half-Space Green’s Function

Abstract In this study, a fast 3D dynamic rupture simulation algorithm, named BIEM_CH (Boundary Integral Equation Method for Complex fault systems in Half-space), is presented. This algorithm, based on exact half-space Green’s functions, supports both structured and unstructured discretization schemes, allowing for the effective handling of a wide range of fault geometries, from simple to complex. Because of the semianalytical nature of the boundary integral equation method, the integral kernel (surface integral of the spatial derivatives of Green’s functions) and rupture processes can be computed separately, making BIEM_CH particularly suitable for applications requiring numerous forward simulations, such as dynamic source inversion, for which only the rupture process needs to be recalculated once the integral kernel is obtained. The performance of the algorithm has been significantly enhanced, achieving up to a hundredfold speed increase through the use of exact closed-form solutions for the time-domain half-space Green’s function and matrix operations leveraging graphical processing unit acceleration, resulting in dynamic rupture simulations that can be completed in a matter of seconds. Moreover, BIEM_CH maintains excellent stability when the mesh dimension does not exceed 375 m, irrespective of whether structured or unstructured discretization schemes are used. In addition, this algorithm demonstrates good agreement with other methods in benchmark exercises conducted by the Southern California Earthquake Center and the U.S. Geological Survey’s dynamic rupture code verification project.