ASMI Archivio Storico Macrosismico ItalianoItalian Archive of Historical Earthquake Data

Improving the knowledge of the seismic history of a region plays a key role in the evaluation of recurrence relations for probabilistic seismic hazard analyses. In this study, we present the results of an investigation carried out in two local historical archives in northeast Sicily, Italy. Several letters, petitions, and reports describing the effects of some earthquakes that occurred between the seventeenth and the eighteenth centuries in the Gulf of Patti area were found and analyzed. This contributed in filling the knowledge gap about a series of moderate‐to‐large seismic events that were overshadowed by catastrophic earthquakes with major impacts both on human losses and cultural heritage. We describe this experience in the hope that other historians will take up the work, looking for other northeast Sicily local archives to investigate because we believe this is the right way toward a better definition of the seismic history of one of the most seismically active regions of Italy.

We present the results of an Italian­Maltese research, carried out to collect the macroseismic data needed to update the seismic catalogue of the Maltese Islands [Galea, 2007]. In this work we adopted the most up­to­date criteria developed by Italian historical seismology, obtaining results that significantly improve knowledge, particularly for the 1650­1923 time­window. Several previously unknown local earthquakes have been identified and evidence has been found of earthquake damage caused to the Maltese Islands both by earthquakes probably located in the Sicilian Channel (1658, 1780, 1861), and by some strong Greek earthquakes (1756, 1810, 1846). The European macroseismic scale 1998 (EMS­98, Grünthal [1998]) was used to assign macroseismic intensities. Basic information on seismic­induced natural phenomena (landslides, tsunamis) was also collected, to be used as a further constraint on the location and size of associated earthquakes, or for paleoseismological studies. As an added bonus, the study collected evidence of some Sicilian earthquakes unknown to seismological literature and data useful to improve the macroseismic database of already known Sicilian and Greek earthquakes.

The Catalogue lists earthquakes that occurred in Italy between 461 B.C. and 1997, and earthquakes that occurred in the general Mediterranean area between the VIII century b.C. and the XV century. This version (CFTI5Med) features: the retrieval and formatting of over 23,000 original bibliographic documents, transcribed or printed, nearly 50% of those utilized in the CFTI5Med. These documents are now available on-line as fully searchable pdf files; a full geological reinterpretation, georeferencing and reprocessing of over 2,300 descriptions of earthquake-induced environmental effects, which are now all available and searchable in a user-friendly web-GIS environment; the elaboration of a number of texts and commentaries that were missing from the CFTI4Med version of the catalogue; a totally re-designed and more efficient web- and web-GIS interface. The new Catalogo dei Forti Terremoti in ltalia includes 1,259 earthquakes that occurred in Italy (98 of which are currently considered false). No commentaries on the main earthquake effects were available in the previous version of the catalogue for 87 of such events as they had not been updated with respect to the information supplied in Guidoboni e Comastri (2005) for the 1000 AD-1500 AD time interval. The commentaries concerning the most significant effects of Italian medieval earthquakes have now been elaborated and are available along with the information on more recent events. For the remainder of the earthquakes first presented with the CFTI4Med - those that occurred in the general Mediterranean area away from the Italian coasts - the new catalogue provides only the felt reports and basic epicentral parameters.

A historical catalogue of felt earthquakes in the Maltese islands has been compiled dating back to 1530. Although no fatalities were officially recorded during this time as a direct consequence of earthquake effects, serious damage to buildings occurred several times. In the catalogue time period, the islands experienced EMS-98 intensity VII-VIII once (11 January 1693) and intensity VII, or VI-VII five times. The northern segment of the Hyblean-Malta plateau is the source region which appears to pose the greatest threat, although large Greek events and lower magnitude Sicily Channel events also produced damage. Estimates of return periods for intensity ≥V are presented, and it is shown that expected peak ground accelerations justify the implementation of, at least, minimum anti-seismic provisions. The rapid and continual increase in the local building stock on the densely-populated islands warrants the implementation of an appropriate seismic building code to be enforced.

A study of some earthquakes (M > 5.3) affecting Southeastern Sicily was performed to define their seismic sources and to estimate seismic hazard in the region. An analysis of historical reports allowed us to reassess intensities of the 1542, 1693, 1818, 1848 and 1990 earthquakes by using the new European Macroseismic Scale 98. The new intensity data were used to define parameters and the orientation of seismic sources. The sources obtained were compared with the ones computed using the MCS intensities retrieved from the Catalogue of Strong Italian Earthquakes. The adopted procedure gives results that are statistically significant, but both the epicentre location and source azimuth, in some cases, are strongly affected by the azimuthal gap in the intensity distribution. This is evident mainly for the 1693 January earthquakes. For these earthquakes the macroseismic data uncertainty gives significantly different solutions, and does not allow the events to be associated with known active faults. By handling the new estimated intensity data and using the site seismic histories, the seismic hazard for some localities was calculated. The highest probability of occurrence, for destructive events (I = 10), was obtained in the area between Catania, Lentini and Augusta, suggesting that the seismogenic sources are located near the Ionian coast.