Correlation in spectral accelerations of European ground motion records

The shape of a Uniform Hazard Spectrum has been criticized to be unrealistic for a site where the spectral ordinates of the UHS at different periods govern by different scenario events and conservative for long-return-period earthquake shaking. Baker and Cornell introduced the Conditional Mean Spectrum (CMS), which considers the correlation of spectral demands (represented by values of ε) at different periods, to address these issues. A CMS estimates the median geometric-mean spectral acceleration response of a pair of ground motions given an M, r pair and a target spectral ordinate, Sa(T 1), for which ε(T 1) is backcalculated using an appropriate attenuation relationship. They developed models for the correlation coefficient ρ ε(T 1) ε(T 2) of ε(T1) and ε(T2), a key component for developing a CMS, using the PEER Strong Motion Database (http://peer. berkeley.edu/smcat/). This paper develops a model for ρ ε(T 1) ε(T 2) using the European earthquake records from the European ground motion database (http://www.isesd.hi.is/ESD-Local/frameset.htm). Epsilon (ε) for each record is computed using Ambraseys ground motion attenuation relationship. The model can be used to develop CMS for European sites and it can be considered to be incorporated in the seismic European standards (Eurocode 8)