A finite difference method was used in a case for the selection of artificial boundary and the effects of different artificial boundaries on numerical simulation results were analyzed to determine the input method of boundary conditions for seismic response analysis of scattering field.Simulation results show that the free-field boundary is more effective than viscous boundary during dynamic finite-difference calculation. A new constitutive model was developed based on FLAC software

linear and nonlinear Mohr-Coulomb models were used for seismic response analysis of two significantly different terrain river valleys. Simulation data show that;the amplification of ground motion is negligible at sites of valley bottom but more obvious at sites of elevated places.When the non-linear is considered

the amplification reduces gradually with the increase of ground motion intensity.Spectral analysis result shows that the high terrains are mainly affected by the high-frequency ground vibration and the flat bottoms are significantly impact by low-frequency ground vibration.