“…SSI can be thought conveniently, both from a conceptual and computational point of view, as the contribution of two concurrent phenomena (Mylonakis et al, 2006): (i) kinematic interaction, in which a massless foundation modifies the motion of the surrounding soil by means of its sole stiffness and (ii) inertial interaction, in which the motion of the foundation itself is further modified by the D'Alembert forces acting in the structure-foundation system. The distinction between kinematic and inertial effects, which also underlies the substructure method, provides a powerful key to interpretation of SSI problems, as observed in experimental works (Rayhani & El Naggar, 2008), numerical works (Mahsuli & Ghannad, 2009;Politopoulos, 2010;Vega et al, 2013) and field measurements (Stewart, 2000;Kim & Stewart, 2003), where many factors can affect the overall dynamic response of the structure. By focusing on the filtering effect, kinematic interaction has been recognised to play a significant role in the case of both embedded (Avilés et al, 2002;Politopoulos, 2010) and deep foundations (Di Laora & de Sanctis, 2013), for which the foundation input motion (FIM) can differ substantially from the free-field motion recorded at ground surface.…”