Seismic soil classification from a different perspective

The simplified seismic soil classification in many countries relies on the Vs30 parameter as a proxy to the amplification factor. The pros and cons of this approach have already been extensively debated in the literature. We present an alternative subsoil seismic classification which is based on expedite geophysical field procedures (passive/active single station and multichannel surveys, all relying on surface waves analysis) aimed at determining the resonance frequencies and the very shallow Vs profile. We show how the major drawbacks of the Vs30-based classification cab ne effectively overcome. In particular, the new approach 1) brings in the concept that the site class is not a universal concept but is strictly linked to the type of structure which is planned to be built on that site, 2) introduces a shift from the ‘depth-domain’ concept (30 m or 20 m or 10 m suggested by different authors) to the ‘frequency-domain’ concept and 3) does not take into account an ‘average’ stiffness but the abrupt stiffness changes, which play a major role in seismic amplification