Empirical ground-motion models adapted to the intensity measure ASA40

Relative average-spectral-acceleration (ASA(40)), a recently developed intensity measure, is defined as the average spectral pseudo-acceleration on the probable interval of evolution of the fundamental frequency of a structure. This article presents two ground motion prediction equations (GMPEs) appropriate for the prediction of ASA(40), using a pan-European strong motion database. Taking advantage of the strong correlation between the new intensity measure ASA(40) and the spectral pseudo-acceleration (SA), existing GMPEs predicting SA can be adapted to predict ASA(40). The first GMPE used in this study is the modified version of a new generation ground motion model, ASB13. In order to decrease the high aleatory uncertainty (sigma) that accompanies predictions when using this modified model, a new model is developed for the prediction of ASA(40). Its range of applicability is for magnitudes M-w from 5.5 to 7.6 and distances out to 200 km, it includes site amplification and it is applicable for a range of periods between 0.01 and 4 s. The proposed model decreases the aleatory uncertainty by almost 15 % with respect to the uncertainty of the modified ground motion model.