Ground-Motion Prediction Equation for SI Based on Spectral Acceleration Equations

Spectrum intensity (SI), defined as the integral of the pseudospectral velocity of a ground motion from 0.1 to 2.5 sec, has recently been shown to be an intensity measure that efficiently predicts the seismic response of both liquefiable and nonliquefiable soil deposits as well as the seismic demands on pile foundations embedded in such deposits. In order for such an intensity measure to be used in performance-based assessment and design, ground-motion prediction relations are required to develop ground-motion hazard curves in terms of SI for various sites. As such relationships developed specifically for SI are sparse, we propose the development of a relationship based on current ground-motion prediction relations for spectral acceleration, which are available in most regions of seismic activity. Comparison with a direct prediction equation for SI provides a validation of the proposed approach. It is illustrated that SI is an intensity measure with a good predictability, thereby further promoting its attractiveness for use in reliability-based seismic response analysis.