Statistical Properties of Nonstationarity in Frequency Contents of Ground Motions Based on Zero-Crossing Rate

Abstract eng:
Considerable attention has been paid to the nonstationarity in frequency contents of ground motions and many methods have been proposed to study this property. But most of these research findings are not suitable for studying the statistical properties and attenuation laws of nonstationarity in frequency contents due to their nonparametric nature, which also blocks their further applications in selection and synthesis of proper ground motions for seismic design. In this paper, zero-crossing rate is used to describe the nonstationary property in frequency contents and an exponential decay model is proposed to represent the zero-crossing rate. Then, the downhill simplex method is employed to estimate the corresponding model (zero-crossing) parameters. By applying the proposed method to ground motions for various magnitudes, epicentral distances and sites, the statistical properties and attenuation laws of zero-crossing parameters are explored and the site-specific zero-crossing parameters are suggested. The work of this paper not only provides a simple and effective approach to study the nonstationarity in frequency contents and its statistical properties, but also gives a more reasonable method to select and synthesize ground motions for seismic design.

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