ASMI Archivio Storico Macrosismico ItalianoItalian Archive of Historical Earthquake Data

The large-scale studies of historical seismology carried out in Italy and Europe in the last decades were mostly aimed at improving knowledge about earthquakes that were already listed in the extant parametric catalogues, rather than at identifying earthquakes that were not listed in them. From 1992 onwards, some of the authors of this study started to look for such “forgotten” earthquakes in different ways (by systematic surveys of serial historical sources, or by extensive investigation of local records in selected areas). More than 2000 pieces of evidence related to as many earthquakes not listed by any seismological compilations/catalogues were thus identified. In 2003 all resources were pooled in a common effort, meant to complete the revision of minor “known” earthquakes carried out by Molin et al. [2008] with a study of the most relevant “unknown” earthquakes identified so far. We present here the results of the analysis of 227 damaging earthquakes, 155 of which are “unknown” to the seismological tradition. Other 72 events were listed in the Postpischl [1985] catalogue, but not in newer parametric catalogues, no evidence of damage being availablefor them at thetime: such evidence has now been found and, in 21 cases at least, it allows for a significant re-evaluation of macroseismic intensity.

This study was started in the frame of an assessment of the completeness of parametric earthquake catalogues. Its primary aim was to check whether early journalistic sources can yield “new” earthquake data, i.e. data on previously unknown damaging earthquakes and previously unknown data on such already known events. Another aim was to assess the quality of the resulting information, an important matter given the widespread opinion that early journalistic sources are highly unreliable. A large sample of monographical (pamphlets) and serial (gazettes) early journalistic sources was systematically searched for “new” earthquake data. The results show them to have a high informative content, while being no more unreliable than most historical sources. It is safe to assume that a large-scale combined effort to put this informative potential within general reach would give a great impetus towards increasing the completeness of the parametric earthquake catalogues of most European (and also non-European) countries.