A critical factor for seismic hazard estimation is a detailed evaluation of the site response. Seismic shaking is highly influenced by the local physical and mechanical properties of the rocks underlying a site. Shallow or thick sedimentary deposits can significantly amplify the earthquake ground motion. Seismologists and engineers have conducted numerous studies to quantify how the seismic energy is modified and how structures that overlie vulnerable soils will behave during strong ground shaking [Wills et al., 2000]. Different methods can be applied to estimate the site response from seismic records. The most frequently used is the spectral ratio method. This approach needs the identification of a reference site, usually characterized by outcropping lithoid rocks, and consists in...