Evaluation of a novel application of earthquake HVSR in site-specific amplification estimation. Issue 139 (December 2020)

• Record Type: Journal Article
• Authors: Zhu, Chuanbin; Pilz, Marco; Cotton, Fabrice
• Is Part Of: Soil dynamics and earthquake engineering. Issue 139(2020)
• Publication Date: 2020-12
• Subjects: Site amplification -- HVSR -- Ground response analysis -- KiK-net -- Earthquake; Soil dynamics -- Periodicals; Earthquake engineering -- Periodicals; Sols -- Dynamique -- Périodiques; Génie parasismique -- Périodiques; 624.176205
• DOI: 10.1016/j.soildyn.2020.106301
• Languages: English
• ISSNs: 0267-7261

Abstract

Abstract: Ground response analyses (GRA) model the vertical propagations of SH waves through flat-layered media (1DSH) and are widely carried out to evaluate local site effects in practice. Horizontal-to-vertical spectral ratio (HVSR) technique is a cost-effective approach to extract certain site-specific information, e.g., site fundamental frequency ( f 0 ), but HVSR values cannot be directly used to approximate the levels of S-wave amplifications. Motivated by the work of Kawase et al. (2019), we propose a procedure to correct earthquake HVSR amplitudes for direct amplification estimations. The empirical correction compensates HVSR by generic vertical amplification spectra categorized by the vertical fundamental frequency ( f 0v ) via k -means clustering. In this investigation, we evaluate the effectiveness of the corrected HVSR in approximating observed linear amplifications in comparison with 1DSH modellings. We select a total of 90 KiK-net (Kiban Kyoshin network) surface-downhole sites which are found to have no velocity contrasts below their boreholes and thus of which surface-to-borehole spectral ratios (SBSRs) can be taken as their empirical transfer functions (ETFs). 1DSH-based theoretical transfer functions (TTFs) are computed in the linear domain considering uncertainties in VS profiles through randomizations. Five goodness-of-fit metrics are adopted to gauge the closeness between observed (ETF) and predicted (i.e., TTF and corrected HVSR) amplifications in both amplitude and spectral shape over frequencies from f 0 to 25 Hz. We find that the empirical correction to HVSR is highly effective and achieves a "good match" in both spectral shape and amplitude at the majority of the 90 KiK-net sites, as opposed to less than one-third for the 1DSH modelling. In addition, the empirical correction does not require a velocity model, which GRAs require, and thus has great potentials in seismic hazard assessments. Highlights: An empirical correction to earthquake HVSR is proposed for direct site amplification estimation. The empirical correction is highly effective and achieves a "good match" with ETF at the majority of the 90 selected sites. 1DSH modelling exhibits a poor performance in predicting amplification with less than one-third of sites having a "good match".