A reappraisal of macroseismic data with statistical analysis for the strongest Calabrian earthquakes of the XVIII to XX centuries (southern Italy)

This study deals with some of the earthquakes that occurred in Calabria from 1783 to 1908. Although they have been largely studied, robust and commonly accepted seismic sources are still missing. Starting from the studies reported in the CFTI5Med catalogue (Guidoboni et al., 2018), we reanalysed historical reports and reassessed the intensity of the shocks by using the European macroseismic scale 98 (EMS), which classifies damage according to its level and vulnerability class of buildings. We revised the 1783 seismic sequence, the 1791 Central Calabria, the 1894 southern Calabria, the 1907 Aspromonte and the 1908 Messina Straits earthquakes. The results obtained are used to compute new source parameters and some statistical analyses. In particular, we used the new compilation of Intensity Data Points (IDP) to carry out a quantitative analysis of the macroseismic intensities distribution, computing the attenuation curves (e.g., Gasperini, 2001) which describe the propagation of the earthquakes in the near and far field and obtaining the main components of the macroseismic intensity for each IDP: isotropic component (II ) and anisotropic component (IA). Considering the anisotropic component (IA) we analyzed the local amplification and attenuation (e.g., De Rubeis et al., 2016) to compare with lithoseismic classes properties of the localities struck by the earthquakes considered. We used approaches adopted in the literature (Sbarra et al., 2019) to determine the approximate hypocenters’ depths and calculated the seismogenic layer by using instrumental data. These analyses allowed a quantitative characterization of the studied historical earthquakes in terms of magnitude, size of the seismogenic sources and allowed us to attribute a seismotectonic domain to the nine earthquakes studied.