Seismic hazard maps of Italy

Abstract

The Italian "Gruppo Nazionale per la Difesa dai Terremoti" has conducted a project in recent years for assessing seismic hazard in the national territory to be used as a basis for the revision of the current seismic zonation. In this project the data on the major earthquakes were reassessed and a new earthquake data file prepared. Definition of a seismotectonic model for the whole territory, based on a structural-kinematic analysis of Italy and the surrounding regions, led to the definition of 80 seismogenic zones, for which the geological and seismic characteristics were determined. Horizontal PGA and macroseismic intensity were used as seismicity parameters in the application of the Cornell probabilistic approach. The main aspects of the seismic hazard assessment are here described and the results obtained are presented and discussed. The maps prepared show the various aspects of seismic hazard which need to be considered for a global view of the problem. In particular, those with a 475-year return period, in agreement with the specifications of the new seismic Eurocode EC8, can be considered basic products for a revision of the present national seismic zonation.