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We present a methodology for the selection of accelerometric time histories as input for dynamic response analyses over vast areas. The method is primarily intended for seismic microzonation studies and regional probabilistic seismic hazard assessments that account for site effects. It is also suitable for structural response analyses if one would like to use a fixed set of ground motion records for analyzing multiple structures with different (or unknown) periods. The proposed procedure takes advantage of unsupervised machine learning techniques to identify zones (i.e., groups of sites) with homogeneous seismic hazard, for which the same set of earthquake recordings can be reasonably used in the numerical simulations. The procedure consists of three steps: (1) data-driven cluster analysis to identify groups of sites with comparable seismic hazard levels for a specified mean return period (MRP); (2) for each zone, definition of a single, reference uniform hazard spectrum (UHS) corresponding to the MRP of interest; (3) selection of a set of accelerometric recordings that are consistent with the magnitude-distance scenarios contributing to the hazard of each zone, and meet the spectrum-compatibility requirement with respect to the reference UHS. An application of the procedure in the Po Plain (Northern Italy) is described in detail. [ABSTRACT FROM AUTHOR]

Seismic microzonation represents a basic tool for prevention activity planning and land management. An extensive and detailed microzonation study was performed with reference to the territory of the Municipality of Cavezzo, damaged during the seismic sequence hitting Emilia-Romagna Region, Northern Italy, in 2012. In this paper, we discuss the work carried out to characterize the spatial variability of ground motion amplification due to local soil conditions in the municipality area. An inter- and multi-disciplinary approach is presented, involving geotechnical engineers, geophysicists, geologists and seismologists from different institutions, to thoroughly characterize the territory using complementary techniques with different level of resolution and confidence. A considerable amount of geomorphological, geological, hydrogeological, seismological, geotechnical and geophysical investigations was collected and processed for the purpose. A GIS-based (Geographic Information System) platform was initially setup to manage the gathered data, which now includes the results of about 1000 geotechnical and geophysical tests. Such an extended dataset was then used as a primary constraint for the creation of a comprehensive pseudo-3D geotechnical and seismo-stratigraphic model of the territory, consisting of a dense grid of one-dimensional vertical profiles to depict the variability of the soil properties over the area. The model was finally used as input for linear-equivalent ground response analysis. For the calculation of the amplification factors, special emphasis was given to the treatment and propagation of the uncertainties of the model parameters, whose different realizations have been accounted through a logic tree approach. • The spatial variability of ground motion was analysed in Cavezzo, Italy. • Geological, seismological, geotechnical and geophysical analyses were performed. • A GIS platform was setup including about 1000 geotechnical and geophysical tests. • A pseudo-3d seismo-stratigraphic model was created to compute amplification factors. [ABSTRACT FROM AUTHOR]