Materiali per un catalogo di terremoti etnei dal 1600 al 1831

Abstract

Mount Etna, together with Vesuvius, are probably the two volcanoes with the longest and most detailed historical records in the world. About ten years ago, the most recent portion of the huge historical data set of Etna was used to compile a macroseismic catalogue of earthquakes occurring in this region from 1832 to 1998 [Catalogo Macrosismico dei Terremoti Etnei, Azzaro et al., 2000]. In the framework of the INGV Working Group on historical earthquake catalogues, the updated release of CMTE [Gruppo di lavoro CMTE, 2014] has become the main data source for the latest version of the Italian parametric catalogue CPTI11 [Rovida et al., 2011]. Historical research on Etna earthquakes was later extended further back in order to cover the previous two centuries. This is a strategic goal, since a relatively small number of earthquakes is listed in the existing repertories for the time-span 1600-1831: there are just 3 events in CFTI4Med [Guidoboni et al., 2007], and only 6 in the latest release of the parametric catalogue of Italian earthquakes CPTI11 [Rovida et al., 2011]; the previous PFG catalogue [Postpischl 1985], which also includes nondamaging -events and those with only epicentral parameters (no intensity data points), lists 26 earthquakes. Thus, it is difficult to believe that there had been so few earthquakes during this time-span - by contrast CMTE reports more than 150 events above the damage threshold in the following two centuries - all the more so as in the 1600-1831 period there were many significant eruptions which would have been accompanied, as usually occurs, by seismic activity. The likeliest explanation is that the available historical record had not been exploited to its full extent and, therefore, many earthquakes were overlooked. To improve this overall scenario, historical research was carried out on the main Sicilian archives as well as regional, Italian and foreign libraries, looking for first-hand sources (diaries, chronicles, official records, travellers’ reports, newspapers) and retrieving more than 200 original documents written between 1600 and 1850. These have been critically analyzed and interpreted to reconstruct the seismic activity, namely identifying the earthquakes and deriving the related intensity data. The result of this work is an inventory of 139 earthquakes occurring in the period from 1600 to 1831, 115 of which are unmentioned in previous studies. Depending on the quality of the collected information, it will be possible in a future step - compiling the catalogue - to calculate the earthquake parameters (epicentre, magnitude, epicentral intensities) for some events, while for the others only generic information on the location (affected areas) and type of macroseismic effects (weakly or strongly felt, damage) will be reported. This paper describes the methodological approach and results of the study and is enhanced by an appendix of short monographs, each of which includes the description of the earthquake effects (or seismic sequence), a list of localities with the associated macroseismic intensities, the transcription of texts and related references.