Seismic classification of Italian municipalities to 2012

Classification of Italian municipalities according to seismic risk as at 2012. In 2003, the criteria for a new seismic classification of the national territory were issued, based on the most recent studies and calculations relating to the seismic hazard of the territory, i.e. the analysis of the probability of the territory being affected over a certain period of time (generally 50 years) by an event exceeding a certain threshold of intensity or magnitude. To this end, Ordinance of the President of the Council of Ministers No 3274 of 20 March 2003 was published in Official Gazette No 105 of 8 May 2003. An update of the National Reference Hazardity Study (Working Group, 2004), provided for in Opc. 3274/03, was adopted by the Prime Minister’s Ordinance No 3519 of 28 April 2006. The new hazard study, annexed to OPCM No 3519, provided the Regions with an updated instrument for the classification of their territory, introducing acceleration intervals (ag), with the probability of being exceeded by 10 % in 50 years, to be attributed to the four seismic zones. Seismic zone 1: AG > 0.25; Seismic zone 2: 0.15 < ag <= 0.25; Seismic zone 3: 0.05 < ag <= 0.15; Seismic zone 4: AG <= 0.05. In compliance with the guidelines and criteria established at national level, some regions have classified the territory in the four proposed areas, while other regions have classified their territory differently, for example by adopting only three areas (zones 1, 2 and 3) and, in some cases, introducing sub-areas to better adapt the rules to the characteristics of seismicity. For the details and meaning of the zones in each region, please refer to the regional regulatory provisions.