Based on the cylindrical wave equation

a method of earthquake input and artificial boundary for seismic soil–structure interaction analysis is presented. The artificial boundary condition is local in both time and space and the earthquake input is implemented at the base of the finite computational domain through a set of nodal equivalent forces

which is proportional to the velocity of the incident seismic wave. The proposed method is simple but efficient; and it can be implemented in finite element method without difficulty. Moreover

the time-stepping algorithm based on Newmark’s method in conjunction with this method is unconditionally stable. Two Numerical examples were conducted to verify the validity and accuracy of the method.