Seismic zone
Zona sismica
A municipality's earthquake hazard class, from 1 (the most hazardous) to 4 (the least hazardous), set by the Regions.
The seismic classification divides Italian municipalities into four zones (zone sismiche) according to the expected ground shaking. The Regions update it with their own decisions and the Civil Protection Department (Dipartimento della Protezione Civile) publishes the national list.
The national criteria use the ground acceleration (PGA) with a 10% probability of being exceeded in 50 years:
| Zone | Expected acceleration | What it means |
|---|---|---|
| 1 | above 0.25 g | the most hazardous, very strong earthquakes possible |
| 2 | between 0.15 and 0.25 g | strong earthquakes possible |
| 3 | between 0.05 and 0.15 g | strong earthquakes possible but rare |
| 4 | up to 0.05 g | the least hazardous |
Some Regions use sub-zones, such as 2A and 2B in Lazio or 3S in Piedmont. The zone is used for planning and to decide which checks apply to building designs. New buildings are designed under the Italian building code (Norme tecniche per le costruzioni), which uses the hazard at the exact point and not just the municipality's zone.
Official source: rischi.protezionecivile.gov.it
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