Selection of accelerometric time histories for the Lazio region (Italy) by clustering of probabilistic seismic hazard data

Selection of accelerometric time histories is a fundamental step in seismic microzonation studies as well as in structural and ground response analyses. In this study, we propose an update of the procedure of Mascandola et al. (2020) for record selection in vast areas, which is based on cluster analysis of seismic hazard data to identify zones (called mesozones) that are homogeneous in terms of seismic hazard. This procedure was applied in the Lazio region in Central Italy. For each mesozone, two conditional spectra (computed for two conditioning oscillator periods) were defined and then adopted as reference for the selection of real accelerometric records. Such records were selected from a large sample of accelerograms that include earthquakes having magnitude and distance consistent with the seismic scenarios controlling the hazard. Before record selection, two algorithms for seismic mesozonation were compared: K-means and spectral clustering. We found that the latter provides a zonation that is more consistent with the spatial distribution of the seismic hazard as well as of hazard disaggregation, and is therefore suggested for record selection in vast areas.