Stochastic Finite-Fault Method Considering Near-Field Ground Motion Directivity Effects

Rapid and accurate estimation of strong ground motions is critical for earthquake disaster response and engineering purposes. The stochastic finite-fault method based on dynamic corner frequency, proposed by Motazedian and Atkinson, has been proven to be a comprehensible and effective approach for generating high-frequency strong ground motion. To facilitate the adaptation of this method in software and engineering practice, we employ GMS2.0 as an enhanced program for simulating stochastic finite-fault ground motion. A key advantage of GMS2.0 is its incorporation of updated models for corner frequency and source duration, which enhances the theoretical consistency of the source model. It also provides users with greater flexibility in defining input parameters, including rupture scaling relations, baseline correction techniques, and crustal amplification models. In this study, the impact of rupture velocity is considered, introducing a relationship between corner frequency and rupture velocity. Furthermore, addressing size effects and propagation directionality of near-fault rupture in the current stochastic finite-fault method, a directionality coefficient, Drup, is proposed. The improved method is applied to simulate near-field strong motions within a 150 km range of the 2012 Ninglang MW5.5 earthquake. Our method demonstrates robust performance over a broad period range, particularly between 0.04 and 4 seconds. This improvement effectively accounts for the impact of rupture propagation direction, providing a more realistic estimation of ground motions for earthquake disaster mitigation.