Key Technical Issues When Developing Probabilistic Foundation Input Response Spectra for Seismic Analysis

Abstract

Many existing nuclear facilities have undertaken updated Probabilistic Seismic Hazard Analysis(PSHA) in response to the March 11, 2011, Great Tohoku Earthquake and subsequent tsunami. For nuclear facilities located in eastern North America the updated PSHA must accurately account for high-frequency (> 10 Hz spectral frequency) ground motions and may include the assessment of site response resulting from site-specific geotechnical conditions. Recent experience at a site in eastern Canada suggests that the assessment of high frequency ground motion critically depends on the site response model. This experience will be summarized including (1) the development of a site geotechnical model that reflects available site data, accounting for epistemic uncertainty and aleatory variability, (2) the derivation of frequency-dependent site amplification factors, and (3) combining the amplification factors with thePSHA results to develop Foundation Input Response Spectra (FIRS), with emphasis on modeling spectral frequencies above 10 Hz.