Floor class | Description of stratigraphic profile | S describing type 1 spectra S describing type 2 spectra | S describing type 1 spectra S describing type 2 spectra |
A | Rock or similar geological formation with a surface layer of up to 5 m of less resistant material | 1.0 | 1.0 |
B | Steep deposits of over-consolidated sand, gravel or clay, at least several tens of meters thick, characterized by a progressive increase in mechanical properties with depth | 1.2 | 1.35 |
C | Deep deposits of medium-density sand, gravel or moderately stiff clay, several tens to several hundreds of meters thick. | 1.15 | 1.5 |
D | Deposits of cohesionless soils of low to medium density (with or without soft cohesive layers) or comprising mostly soft to firm cohesive soils. | 1.35 | 1.8 |
E | Soil profile comprising a superficial layer of alluvium with vs values of class C or D and a thickness of between approx. 5 m and 20 m, resting on a stiffer material with vs > 800 m/s | 1.4 | 1.6 |