The behavior of structures subjected to earthquakes demonstrates that the phenomena of soil-structure and fluid-structure interaction have a great influence on the structural response, especially in the case of structures such as dams, tanks, elevated water tanks, marine platforms, intake towers, etc. The numerical study of these phenomena requires solving problems in which the coupling between two solids or between a solid and a fluid occurs only at the surfaces of contact between them. This chapter describes several numerical procedures used to solve the problem of seismic interaction. For this, it is necessary to have a record of seismic motion on the interface that separates the area of the soil considered in the analysis, which defines a theoretical surface sometimes called base rock. Below this, the soil can be assumed infinitely stiff or with a certain flexibility. To obtain an accelerogram at the level of the base rock, a deconvolution of the seismic motion available on the ground surface must be made. Then, this calculated accelerogram is applied on the soil-structure-fluid system.