A Parallel Grid-Search Procedure to Constrain Rupture Depth and Velocity in Finite-Fault Earthquake Source Modeling

Uncertainty in key input parameters, particularly rupture initiation depth (focal depth) and average rupture propagation velocity, can significantly degrade the reliability of finite-fault earthquake source modeling results. These parameters are often estimated empirically or determined through trial-and-error, leading to solutions with large uncertainties and inefficient computation. To address this problem, we develop a parallel grid-search procedure that systematically constrains initial rupture depth and rupture velocity prior to performing a final source rupture modeling. The method evaluates a two-dimensional grid of depth–velocity models by assigning subsets of the grid in parallel to multiple CPU threads. Compared to conventional sequential grid search, the computation time is dramatically reduced. Misfit variance contours are then used to identify the optimal parameter combinations, providing reasonable initial conditions for subsequent rupture inversion. The procedure is validated using three large earthquakes with diverse tectonic environments, demonstrating its efficiency, robustness, and applicability to modern large-scale seismic modeling. This approach offers a practical and scalable solution for improving the accuracy of finite-fault earthquake source modeling.