For buildings with or without basement, the internal forces to be transferred from the building to the foundation are determined automatically.
The “structural” components are typically analyzed using standard strength design load combinations and methods whereas the adjacent soil components are analyzed using allowable stress design (ASD) practices, in which earthquake forces (that have been reduced by R) are considered using ASD load combinations, to make comparisons of design forces versus allowable capacities. These “allowable” soil capacities are typically based on expected strength divided by a factor of safety, for a given level of potential deformations.