Civil-protection ordinance that reclassified the entire Italian territory into four seismic zones of decreasing hazard, ending the existence of 'non-seismic' areas, and set the first technical criteria for building in seismic zones (later replaced by the NTC). Published in Official Gazette no. 105 of 8 May 2003.
It concerns the whole national territory for classification purposes, and works in seismic zones. Today seismic design is governed by NTC 2018 and the controls by D.P.R. 380/2001; the operational zone lists are adopted and updated by the Regions.
Until 2003 wide portions of the territory were not classified as seismic, and there people built without anti-seismic criteria. After the San Giuliano di Puglia earthquake (2002), OPCM 3274/2003 reclassified the whole country: there are no longer 'non-seismic' areas, but four zones of decreasing hazard. With the reclassification came a new generation of seismic technical rules, built on limit states and capacity design, in the wake of Eurocode 8. These were not Italy's first anti-seismic criteria — a national seismic code had existed at least since Royal Decree-Law 640/1935 and Law 64/1974 — but the change of generation is what counts.
The seismic zone remains the administrative frame, but structural design no longer starts from the zone: NTC 2018 (D.M. 17/01/2018) compute the seismic action site by site, from the coordinates and the base hazard, adjusted for the subsoil category and the reference period of the works. The zone tells you 'where we are in the national picture'; the NTC tell you 'how much seismic action to apply here'.
Operational classification is the responsibility of the Regions, which adopt and update the lists of municipalities by zone on the basis of the state criteria. As for controls, D.P.R. 380/2001 (the Consolidated Building Act, Part II) governs authorisations, filings and supervision of construction in seismic zones, with obligations graduated by zone and type of works.
Classification also governs policies and incentives: mapping seismic risk is the precondition for measures such as the Sismabonus and for planning prevention. It is the level at which Italy chose, after 2003, to treat its whole territory as exposed — to differing degrees — to the action of earthquakes.
It reclassified the whole national territory into four seismic zones, removing unclassified areas, and introduced a new generation of seismic technical rules, built on limit states and capacity design. These were not Italy's 'first' anti-seismic criteria: a national code had existed at least since Royal Decree-Law 640/1935 and Law 64/1974. Those technical annexes were later superseded by the NTC.
No: sizing follows NTC 2018 with the hazard parameters of the specific site. The zone has administrative and control value, it is not the design value.
Four: Zone 1 is the most hazardous, Zone 4 the least. The associated acceleration (ag) ranges were defined by OPCM 3519/2006.
The Regions, which adopt and update the lists of municipalities by zone on the basis of the state criteria.
Belonging to zones 1, 2 or 3 is a condition of access to the Sismabonus — zone 4 is excluded. It is not, however, a grading criterion: the rate is the same in all three admitted zones. Classification is the precondition of the measure, not its dosage.