Nonlocal period parameters of frequency content characterization for near‐fault ground motions

SUMMARY This paper focuses on the frequency property analysis of near‐fault ground motions with and without distinct pulses, separately from the Chi‐Chi and Northridge earthquakes. Ten scalar period parameters of ground motions, especially several nonlocal period parameters, are considered. Two new nonlocal parameters, namely the mean period of Hilbert marginal spectrum (Tmh) and the improved characteristic period (Tgi), are suggested. Moreover, comprehensive comparison and analysis indicate that Tmh, Tgi and Tavg (average spectral period) can distinguish the low‐frequency components of near‐fault ground motions; Tm (mean period of Fourier amplitude spectrum) and To (smoothed spectral predominant period) represent the moderate‐ and high‐frequency components, respectively. The variance coefficient of predominant instantaneous frequency of Hilbert spectrum (Hcov) can be regarded as an alternative index to measure the non‐stationary degree of near‐fault ground motions. Finally, the velocity pulses and earthquake magnitude remarkably affect the frequency parameters of near‐fault ground motions.