Evaluation of Damages to the Architectural Heritage of Naples as a Result of the Strongest Earthquakes of the Southern Apennines

The city of Naples (Campanian region, Southern Italy) has been hit by the strongestearthquakes located inside the seismogenic areas of the Southern Apennines, as well as bythe volcano-tectonic earthquakes of the surrounding areas of the Campi Flegrei, Ischia andVesuvius volcanic districts. An analysis of the available seismic catalogues shows that in thelast millennium, more than 100 earthquakes have struck Naples with intensities rating I to III onthe Mercalli-Cancani-Sieberg (MCS) scale over the felt level. Ten of these events have exceeded thedamage level, with a few of these possessing an intensity greater than VII MCS. The catastrophicearthquakes of 1456 (I0=XI MCS), 1688 (I0=XI MCS) and 1805 (I0=X MCS) occurred in theCampania-Molise Apennines chain, produced devastating effects on the urban heritage of the cityof Naples, reaching levels of damage equal to VIII MCS. In the 20th century, the city of Naples washit by three strong earthquakes in 1930 (I0=X MCS), 1962 (I0=IX MCS) and 1980 (I0=X MCS),all with epicenters in the Campania and Basilicata regions. The last one is still deeply engravedin the collective memory, having led to the deaths of nearly 3000 individuals and resulted in thenear-total destruction of some Apennine villages. Moreover, the city of Naples has also been hit byancient historical earthquakes that originated in the Campanian volcanic districts of Campi Flegrei,Vesuvio and Ischia, with intensities up to VII-VIII MCS (highest in the Vesuvian area). Based onthe intensity and frequency of its past earthquakes, the city of Naples is currently classified in thesecond seismic category, meaning that it is characterized by "seismicity of medium energy". In thispaper, we determine the level of damage suffered by Naples and its monuments as a result of thestrongest earthquakes that have hit the city throughout history, highlighting its repetitiveness insome areas. To this aim, we reconstructed the seismic history of some of the most representativeurban monuments, using documentary and historical sources data related to the effects of strongearthquakes of the Southern Apennines on the city of Naples. The ultimate purpose of this study is toperform a seismic macro-zoning of the ancient center of city and reduce seismic risk. Our contributionrepresents an original elaboration on the existing literature by creating a damage-density map of thestrongest earthquakes and highlighting, for the first time, the areas of the city of Naples that are mostvulnerable to strong earthquakes in the future. These data could be of fundamental importance tothe construction of detailed maps of seismic microzones. Our study contributes to the mitigation ofseismic risk in the city of Naples, and provides useful advice that can be used to protect the historicalheritage of Naples, whose historical center is a UNESCO World Heritage site.Appl. Sci.2020,10, 6880; doi:10.3390/app10196880www.mdpi.com/journal/applsci Page 2 Appl. Sci.2020,10, 68802 of 29Keywords:Naples (Southern Italy), historical earthquakes; Southern Apennine; seismic hazard1. IntroductionSince historical times, the central-southern Apennines chain has generated the strongestearthquakes in Italy. The epicenters of the most energetic events located along this chain haveshown a significant alignment in the northwest-southeast direction, parallel to the main direction ofthe Apennines (Figure 1). The city of Naples has always been exposed to strong earthquakes, andthese repeatedly have hit the Southern Apennines from the 15th century to the present (Appendix ATable A1) [1-4]. Our analysis of the available earthquake catalogues and relative scientific papersshows that more than 100 earthquakes with intensities of I-