An alternative construction of normalized seismic design spectra for near-fault regions

Abstract

This paper presents a methodology for constructing seismic design spectra in near-fault regions. By analyzing the characteristics of near-fault pulse-type ground motions, an equivalent pulse model is proposed, which can well represent the characteristics of the near-fault forward-directivity and fling-step pulse-type ground motions. The normalized horizontal seismic design spectra for near-fault regions are presented using recorded near-fault pulse-type ground motions and equivalent pulse-type ground motions, which are derived based on the equivalent pulse model coupled with ground motion parameter attenuation relations. The normalized vertical seismic design spectra for near-fault regions are obtained by scaling the corresponding horizontal spectra with the vertical-to-horizontal acceleration spectral ratios of near-fault pulse-type ground motions. The proposed seismic design spectra appear to have relatively small dispersion in a statistical sense. The seismic design spectra for both horizontal and vertical directions can provide alternative spectral shapes for seismic design codes.