Stochastic modelling of the pulse-like near-fault ground motions with time-frequency representation

Seismic near-fault ground motions differ from those in the far-field. They could contain large amplitude and long period velocity pulses and cause damage to structures. In the present study, we propose a new stochastic model for the pulse-like near-fault ground motions by considering the earthquake magnitude, site-to-source distance, and soil condition. The proposed model consists of the pulse-like (PL) and non-pulse-like (NPL) components. The PL component is represented by using parametric models from literature; the NPL component is characterized using the S-transform. A time- and frequency-dependent power spectral density model for the NPL component is proposed, where the frequency modulation and the amplitude modulation are implicitly considered. Probabilistic predicting equations for evaluating the parameters of the proposed stochastic model are developed by considering the selected ground motions records with pulse-like motions extracted from Next Generation Attenuation–West 2 (https://ngawest2.berkeley.edu/) database. The use of the proposed model to generate pulse-like near-fault ground motion is illustrated by numerical examples. The model is validated by comparing the pseudo-spectral acceleration of the simulated records and actual records.