ABSTRACT
The accurate definition of a safe, but not overestim ated, earthquake loading to structures, is always a formidable task since the detailed characteristics of a future earthquake may vary w ithin wide ranges of m ultiple param eters. For practical applications seismic ground motions are expressed commonly in the form of response spectra, obtained by treating statistically a sample of response spectra derived from a number of acceleration records. This simple procedure was first used by [1] and [2] to develop horizontal and vertical design response spectra for nuclear facilities.
