Ground motion records, selected as an input for engineering seismic analysis of structures, are required by codes to reflect the hazard at site of the construction and also, at least in Europe, to be consistent with the features of the seismic sources in the region. In the most of cases, while the former issue is addressed via a prescribed design spectrum, the latter, which basically consist in defining a design scenario, is left unsolved to the practitioner. However, if the design spectrum is derived from probabilistic seismic hazard analysis, disaggregation may be helpful in the matter, allowing to identify the contribution to the hazard of each source (in terms, for example, of source-to-site distance and magnitude) for the spectral ordinate of interest. It is well established that such an information can address the identification of scenarios relevant for design; i.e., the design earthquakes.

The presented work discusses the identification of code-consistent engineering design earthquakes referring, as an example, to the Italian case. Because disaggregation results change with the spectral ordinate and return period, the considered hazard refers to peak ground acceleration (PGA) and 1s spectral acceleration (to represent low and high period regions of the response spectrum) with four exceedance return periods between 50 and 2475 years. After hazard is computed, strategies for the identification of design earthquakes starting from the disaggregation distributions of each site are discussed and results are mapped for the whole country. Issues, such as sites with multiple design earthquakes and dependence of disaggregation results from structural features and design limit state, are also addressed.