WIT Press

Assessment Of Seismic Potential In Southeastern Sicily


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S. Gresta & H. Langer


Southeastern Sicily has been struck several times by large earthquakes (1 169, 1542, 1693) each with MCS-Intensities of X-XI degrees (and estimated magnitudes around 6.5 to7). The area thus belongs to the zones with the highest seismic potential in Europe. Following probabilistic analyses, which were carried out on a national scale, estimated peak accelerations with a return period of 475 years here amount to ca. 20% of g. This is significantly less than reported for other active seismic zones in Italy, where comparable or even lower maximum intensities are reported. In this work GIS based electronic maps have been created for the county of Catania exploiting the rich material of seismic logs, which allows the identification of the characteristic lithological units in the sense of EC8-soil classes. The maps were constructed using empirical relations between peak ground acceleration and macroseismic intensities of each municipality within the county. Local geological conditions are accounted for by applying correction factors following a strategy similar to the U.S. Uniform Building Code. Finally thematic maps of pseudo acceleration were created for typical buildings of the area, with eigenfrequencies of 1 and 5 Hz, respectively. These analyses are backboned by synthetic site dependent strong ground motion simulations carried out for selected sites in several urban areas of the County. Various earthquake scenarios have been taken into account, which underscore the considerable damaging potential even of moderate sized local earthquakes. The higher level of seismic potential derived from the empirical and synthetic approaches is in better agreement with the observed damages caused by the