Seismic Demand on Historical Constructions During the 2016–2017 Central Italy Earthquake Sequence

Between August 2016 and January 2017 nine shallow events with moment magnitude between 5.0 and 6.5 occurred in Central Italy, with largest magnitude being the most severe in Italy since 1980. Several thousands of heritage buildings have been affected to a different degree by the ground motion shaking, highlighting some specific behaviours in the most stricken areas. In and around Amatrice extensive masonry fragmentation, cracking of large walls without openings, as well as survival of tall towers and slender bell gables have been observed. On the contrary, in and around Norcia bell gables and churches collapsed. In this paper, surveyed response is interpreted both in terms of construction characteristics and by means of conventional (pseudo-acceleration) and unconventional (energy and rocking) spectra. It is shown that in Amatrice high frequency content of the first earthquake affected short masonry structures with very poor quality mortar, whereas in Norcia low-frequency content affected structures undergoing out-of-plane rocking or local mechanisms.