GNGTS 2013 - Atti del 32° Convegno Nazionale

Ground-motion predictive equations for low-magnitude earthquakes in the Catania province: the case of volcanic area of Mount Etna G. Tusa, H. Langer Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Etneo - Sezione di Catania, Italy Introduction. The province of Catania undergoes high deformation rates which entails a considerable level of crustal seismicity and is thus one of the highest seismic hazard areas in Italy. Besides heavy damage caused by earthquake activity on a regional scale, the seismicity on Mount Etna leads to a rather peculiar scenario where rather small but superficial earthquakes produce severe damage on a local scale. This superficial seismic activity is associated to local surface tectonic structures of Mount Etna, such as the Pernicana Fault system, the Northern and Southern Rift, and the Timpe Fault System (Bosquet and Lanzafame, 2004), and is characterized by a high frequency of earthquakes, moderate magnitude of the events, often clustered in swarms, and focal depths often less than 3 km (Gresta and Patanè, 1987). The shallow earthquakes affect the whole volcanic area, even if they are more numerous in its central-eastern portion. Despite their small magnitudes, they have caused severe effects at the surface with macroseismic intensities reaching values up to X EMS (Azzaro, 2004). The most recent examples of destructive earthquakes within the volcanic edifice belong to a seismic swarm (formed by some hundreds of events) that occurred on Mt. Etna between 26 and 29 October 2002. Several of these earthquakes were clearly felt by the population in an area from Messina to Siracusa. The most damaging event of the swarm was the Santa Venerina earthquake on 29 October 2002, which had a magnitude of M L 4.4. This event struck a densely urbanized area on the southeastern flank of the volcano. Macroseismic intensities reached degrees up to VIII (EMS with major damage even to reinforced concrete structures). Fig. 1 – Map of study area. The area belonging to the province of Catania is delimited by the gray line. Triangles represent the stations of the RSPSO; circles, epicenter locations of the Shallow Mt. Etna Events used in this study. 153 GNGTS 2013 S essione 2.1