Site Effects from the Building Scale to the Seismic Microzonation Scale: Examples from the Experience of L'Aquila

This paper illustrates the site characterization for evaluating local ground motion amplifications at two sites in the urban area of L'Aquila, performed for the reconstruction of buildings damaged by the April 6, 2009 earthquake. The paper is focused on the comparison between results obtained from site investigations carried out at the building scale and from information contained in the seismic microzonation study. Local amplifications inferred from microzonation may be considerably different from those provided by ground response analyses based on punctual soil data, due to the complex geological setting and the marked variability in geotechnical properties of the foundation soils. The practice of using seismic microzonation data for deriving the seismic action on buildings, not infrequent in structural engineering design, should be avoided or considered with caution.