Vs30 profile

The V_s,30 is a suitable average measure of the shear (S) waves propagation velocity in the soil, within the first 30 meters of depth from the ground level.

It is defined as follows:

where h_i and V_i are the thickness (in m) and the shear wave velocity V_s (in m/s) of the N soil layers present within the first 30 m.