EC8 site category

The seismic site classification is based on the stratigraphic and dynamic properties of the soil profile. Site classes are defined according to the Eurocode 8 as follows:

-Class A: rock or other similar geologic formation, including 5 m (maximum) of surface weathered material. Vs,30 > 800 m/s (see V_s,30);

-Class B: very dense sand or gravel, or very consistent clay, in soil deposits at least several tens of meters depth, characterized by a gradual increase of dynamic properties with depth. 360 m/s < Vs,30 < 800 m/s;

-Class C: medium dense sand or gravel, or consistent clay, in deposits with depth between several tens to hundreds of meters. 180 m/s < Vs,30 < 360 m/s;

-Class D: loose to medium dense non-cohesive soil deposits (with or without cohesive soil layers), or medium consistency cohesive materials. Vs,30 < 180 m/s;

-Class E: soil profile consisting of a shallow alluvial layer with Vs values typical of C or D class, and thickness between about 5 m and 20 m, lying on a material with Vs,30 > 800 m/s;

-Class S1: deposits consisting of - or containing one layer at least 10 m thick - high plasticity clays/silts (P1 > 40) with a high water content;

-Class S2: soil deposits susceptible to liquefaction, or sensitive clays, or any other profile which is not included in the A-E or S1 classes.