Current methods cannot simulate the infinite property and complexity of the heterogeneous foundation synchronously. In this paper, the concrete dam and the unbounded foundation were simulated by the scaled boundary finite element method (SBFEM). The remarkable advantage of this method is that it can reflect the infinite behavior of the foundation exactly. The most important is that no additional computational effort is needed when simulating the faults in the foundation. The study result shows that the existence of faults would generate an influence on seismic response in different extents, and cause the redistribution of earthquake stresses, even stresses to be concentrated partially. So the effect of the presence of faults should be taken into consideration.