Significance of site natural period effects for linear site amplification in central and eastern North America: Empirical and simulation-based models

Abstract

This article evaluates linear simulation-based and empirical site amplification models including site natural period dependency parameters to account for the distinctive amplification behavior near site fundamental frequencies resulting from the sharp impedance contrast between soil and underlying hard bedrock in central and eastern North America (CENA). The simulation-based amplification models are developed using 581,685 frequency-domain linear analyses generated from a parametric study and include V_S30-scaling and site natural period (T_nat) parameters. The empirical models are derived from residuals analyses of ground-motion models for two reference conditions: B/C boundary (V_S30 = 760 m/s) and CENA hard-rock condition (V_S = 3000 m/s). The simulation-based and empirical models are compared for 8 site profiles in CENA to measured horizontal-to-vertical (H/V) component response spectral (RS) ratios, the mean of linear simulations for similar sites, and one-dimensional (1D) linear site response analysis for four of these sites. Comparisons between observed and estimated site amplification behaviors highlight model dependency on T_nat in CENA. Model consistencies and differences related to the distinct linear amplification features near site fundamental frequency are discussed.