Soil-structure interaction (SSI) is a phenomenon in which the response of the structure and its underlying soil influence each other. When an earthquake affects a given structural system resting on its supporting ground, neither the structure nor its underlying soil can act independently.

The SSI should be considered as the combination of two different interaction mechanisms: Kinematic and Inertial. The Kinematic Interaction is the response of the soil body with a massless rigid foundation system under seismic excitation. The Inertial Interaction is the response of the full soil-pile-structure system subjected to the motion captured from the Kinematic Interaction mechanism.