Suitability of the 1D Assumption for Ground Response Analysis in the Epicentral Area of the 2016 Mw 6.0 Amatrice Earthquake (Central Italy)

Abstract The 2016–2017 Central Italy seismic sequence was recorded by the 3A network deployed in the epicentral area and composed of 50 seismic stations. Taking advantage of microzonation activities, we retrieved site information for a subset of these stations, including shear-wave velocity profiles from down-hole tests down to a minimum depth of 30 m. In this paper, we compared the theoretical 1D transfer functions, computed from site information with the STRATA code under the linear-elastic assumption, to the empirical amplification functions derived by weak-motions spectral ratios, using either a reference site (SSR) or horizontal-to-vertical ratios (EHV). The poor match between empirical and theoretical amplification functions suggests that the 1D assumption may not hold for most sites. To support this observation, we applied different classification strategies to discriminate those sites that can be interpreted as having a 1D site response.