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 VS30-scaling and site natural period ( Tnat) parameters. The empirical models are derived from residuals analyses of ground-motion models for two reference conditions: B/C boundary ( VS30 = 760 m/s) and CENA hard-rock condition ( VS = 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 Tnat in CENA. Model consistencies and differences related to the distinct linear amplification features near site fundamental frequency are discussed.

The influence of multiple impedance contrasts on mHVSR site period estimates in the Canterbury Plains of New Zealand and implications for site classification

“…Thus, these additional metrics are neglected or default values are assumed. In these cases, shallow geophysical testing to provide near-surface V S profiles coupled with mHVSR testing to identify periods of vibration above deep impedance contrasts may provide significant insight into the response of the soil strata (as demonstrated by Hashash et al, 2020; Hassani and Atkinson, 2018). The data presented in this article strongly support the use of site period estimates obtained from mHVSR measurements as a means to better model and understand site response.…”

“…Hassani and Atkinson (2018) found that the site effects model for Central and Eastern North America (CENA) was best constrained by a combination of site period and V S30 . Further ground motion simulation studies note that site period is necessary to constrain GMPE site effect amplification terms in the CENA region (Hashash et al, 2020). Zhu et al (2020) found that site period coupled with V S30 were the best metrics, among Z 0.8 , Z 1.0 , Z 2.5 , and several average shear wave velocities, to model the empirical site amplification observed in a dataset from the Japanese KiK-net downhole seismic arrays.…”

Application of empirical and simulation-based site amplification models for Central and Eastern North America to selected sites

“…These resonance effects are also commonly observed across broad inventories of CENA sites in empirical studies (Hassani and Atkinson, 2016, 2017); and in site response simulations (Harmon et al, 2019a, 2019b). Hashash et al (2020b) further describe the compatibility between empirical site fundamental frequency ( f peak )-based (Hassani and Atkinson, 2016, 2017); and simulation-based L3 site amplification functions.…”

An open-source site database of strong-motion stations in Japan: K-NET and KiK-net (v1.0.0)

“…Thus, the past few years have seen many studies searching for an alternative or complementary site indicator to V S30 , for example, depth parameter and site resonant frequency (e.g. Ghofrani and Atkinson, 2014; Hashash et al, 2020; Hassani and Atkinson, 2018; Pitilakis et al, 2013; Zhu et al, 2020c).…”