Taxonomy for evaluating the site-specific applicability of one-dimensional ground response analysis

Abstract

Because one-dimensional (1D) ground response analysis remains the state-of-practice for geotechnical earthquake engineering, one crucial task is to identify whether the response of a site can be modeled well by 1D analysis. In this study, ground response analyses incorporating 1D transfer functions (TF) and the H/V Spectral Ratio (HVSR) technique are carried out for 34 downhole array sites and used to develop a taxonomy that assesses the suitability of 1D analysis for a site. The empirical HVSR is used to identify the first-mode resonant frequency of the site, and the within and outcrop TF are used to distinguish true outcrop-resonances from pseudo-resonances. The taxonomy is focused on capturing outcrop-resonances rather than pseudo-resonances because pseudo-resonances are an artifact of downhole array sites and are not present in the outcropping analysis of non-downhole array sites. Using the proposed taxonomy, 69% of the sites are considered suitable for 1D analysis, which is a much larger percentage than found in other studies. This more favorable result is a direct result of considering only true-resonances in the assessment of 1D applicability. This taxonomy system is developed using downhole array data but it can be applied to any site (even non-downhole array sites) in which the empirical HVSR curve and shear wave velocity profile are measured, making it easily applied in engineering practice.