Abstract

Based on the 72 free‐field accelerograms with the closest site‐to‐rupture distances (Rrup) less than 300 km in the 2013 moment magnitude (Mw) 6.7 Lushan earthquake, this work calculates the four simplified frequency‐content parameters (the mean period [Tm], the predominant spectral period [Tp], the average spectral period [Tavg], and the smoothed spectral predominant period [To]) and compares the calculation results with empirical models. For the Lushan earthquake, the spatial contours of the recorded frequency‐content parameters show that the long‐period (>1  s) region is observed in the southwest of the study area, with Rrup>200  km. The long‐period region is mainly caused by the Quaternary basins that are distributed along‐strike directions of many large faults. When predicting the frequency content of ground motions for the Lushan event, the models of Lee (L09) and Rathje et al. (RFRB04) for T0 exhibit the best‐predictive efficiency. For the parameter Tm, the quantitative assessment of all models indicates that the Du (DU17) model is the most efficient. The comparison between the recorded frequency‐content parameters of the Lushan event and empirical models shows that the frequency content of strong motions is region dependent. All models’ intraevent residuals for the four parameters are less for Rrup100  km than for Rrup>100  km. The maximum positive intraevent residual for To is near or in the long‐period region, which indicates the effect of geology structure on the recorded frequency‐content parameters of strong motions.

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