Mount Etna eruptions and damaging earthquakes: new insights

Between 26 and 29 October 2002, the Mt. Etna area was struck by a seismic swarm that counted some hundred events some of them well felt by the population. A first group of epicenters is located in the E-NE part of the volcano, reaching a maximum local magnitude of 4.6 on October 27 at 02:50 UT. A second group, occurring since October 28, is located in the SE flank close to the town of Zafferana Etnea and culminated with the ML 4.4 earthquake of October 29 at 10:02 UT. The seismic swarm was concomitant with the opening of a system of fractures in the eastern part of the volcano and the reactivation of the eruptive fracture system originated by the 2001 eruption. The most damaging event was the ML 4.4 earthquake of October 29, which occurred in a densely urbanized territory and attained intensity VIII on the European Macroseismic Scale (EMS). In spite of its small local magnitude, the shock caused significant damage to many buildings including reinforced concrete ones in an area that extends for about 4 km in a NNW-SSE direction and is centered around the villages of S. Venerina and Guardia. A long system of surface fractures originated along the damaged area. Other similar and even stronger events of the 2002 swarm in the northern zone did not cause diffuse damage since they occurred in a not densely urbanized area; however, they were highly destructive for the few sparse buildings close to the epicenters. The sequence was well recorded by the Broad Band Station of Antillo (Mednet Network), the most energetic events also triggered the Strong Motion Stations of Bronte (BRNT) and Catania (CATA). The latest part of the sequence (Dec. 2003 – Jan. 2004) was recorded by the local micronetwork installed in Santa Venerina (SVN). Two of these stations were also operating in Santa Venerina from Nov. 2003 to Aug. 2004. Moreover, data from a broad band station installed in Catania are available from Mar. 2001 to Dec. 2001