Synthesis of the time-frequency non-stationary stochastic near-fault fling-step ground motion based on time-frequency non-stationary ground motion model and stochastic pulse model

Near-fault fling-step ground motions (NFFS-GMs) are known to cause significant permanent ground displacements, resulting in greater structural damage for long-period flexible structures compared to far-field ground motions. Furthermore, even during the same seismic event, the pulse parameters—such as permanent ground displacements Dsite and pulse period Tp—can vary considerably. Despite their importance, research on stochastic NFFS-GMs remains limited. To address this gap, this paper proposes a method for synthesizing the time-frequency non-stationary stochastic near-fault fling-step ground motion for a specific seismic scenario. Firstly, we employ the discrete wavelet transform (DWT) method, utilizing five mother wavelet functions (MWFs) to analyze 210 Chi-Chi ground motions. This analysis identifies 41 valid NFFS-GMs. The effectiveness of the identification method is validated by comparing the displacement time histories of the original ground motion. Pulse parameters are subsequently derived using the fling-step (FS) pulse model proposed by Abrahamson, in conjunction with the nonlinear least-squares method. A regression model correlating pulse parameters with the seismological parameter of the fault distance R is then developed through Pearson correlation analysis and the nonlinear least-squares method. The residuals of the regression model σlnDsite and Tp are treated as random variables, and their probability distributions are determined. After that, a new stochastic pulse model is introduced to simulate low-frequency ground motions, while a time-frequency non-stationary model is used to simulate high-frequency ground motions. These components are synthesized in the frequency domain to obtain the time-frequency non-stationary stochastic near-fault fling-step ground motion (TFNS-SNFFS-GM) via inverse Fourier transform. Finally, the effectiveness of the proposed method is confirmed by comparing the response spectrum of the synthesized ground motion with that of actual NFFS-GMs. •A new method for simulating TFNS-SNFFS-GMs was proposed.•DWT with five MWFs was applied to identify the pulse parameters of fling-step GMs.•A new stochastic pulse model was proposed for synthesis of SNFFS-GMs.•The formulas between fling-step parameters (lnDsite and t1) and R were derived.