ORIGINAL ARTICLE Broadband (0.05 to 20 s) prediction of displacement response spectra based on worldwide digital records Carlo Cauzzi & Ezio Faccioli Received: 6 December 2007 / Accepted: 3 March 2008 / Published online: 29 April 2008 # Springer Science + Business Media B.V. 2008 Abstract A new set of empirical equations for prediction of displacement response spectral ordinates from 20 Hz to T =20 s is illustrated. The coefficients of the equations were obtained by regressing a dataset based on 1,155 tri-axial digital and 9 analog acceler- ometer records from 60 earthquakes worldwide. Long period disturbances in the accelerograms were evalu- ated and removed using a very recent method, aimed at preserving the long-period spectral content of the records. Analysis of variance has disclosed only little evidence for regional dependence of ground motions, while a carefully conducted evaluation of site effects resulted in clearly differentiated spectral amplification bands associated to the main ground types B, C, and D of Eurocode 8. Spectral ordinates for vibration periods >5 s were found to scale with magnitude quite consistently with theoretical scaling from Brune’ s model. On the other hand, comparison of results with those yielded by recent prediction models in Europe and the United States (NGA), indicated that the latter may not be uniformly reliable at long periods. The proposed empirical equations are easily implemented in computer programs for seismic hazard assessment, being characterized by a simple functional form and a restricted number of predictor variables. Keywords Attenuation relationships . Digital accelerograms . Displacement-based design . Displacement response spectra . Ground motion prediction . Long-period ground motion 1 Introduction Following the developments of the last 10 years, which placed strong emphasis on displacement con- siderations and capacity design concepts (Park and Paulay 1976), the earthquake resistant design of structures has increasingly become performance- based. In this process, the primary descriptor of the seismic demand becomes the relative displacement of the structure caused by the imposed ground motion, quantified through the displacement response spec- trum (hereafter DRS). In particular, among the different methods for displacement-based design proposed in recent years, the direct displacement- based design approach (Priestley et al. 2007) replaces the actual structure (a nonlinear multi-dof system) with an equivalent linear 1 dof system, in which energy dissipation due to nonlinear response is J Seismol (2008) 12:453–475 DOI 10.1007/s10950-008-9098-y Electronic supplementary material The online version of this article (doi:10.1007/s10950-008-9098-y) contains supplementary material, which is available to authorized users. C. Cauzzi (*) : E. Faccioli Department of Structural Engineering, Politecnico di Milano, Piazza Leonardo da Vinci, 32, 20133 Milan, Italy e-mail: cauzzi@stru.polimi.it E. Faccioli e-mail: faccioli@stru.polimi.it