To the deep soil deposit

for which the shear velocity is less 500m/s

while the burial depth is 100 m

the present methods dealing with the basement in seismic response computation are discussed.Based on theoretical analysis and engineering cases

3basement models（linear extrapolation

soft interlayer assumption and stiff basement）are made.The models’ dynamic response under different seismic intensity is calculated by 1Dequivalent linearization routines and the relative soil nonlinear parameters are provided by experiments.The PGA and response spectra are compared and the results show the stiff basement model is more favorable in engineering application

which is simple and compatible.The effect of wave velocity of stiff basement on seismic response is numerically analyzed and a proper wave velocity ratio between upper soil and basement is recommended.