Abstract:The nonlinearity of soil has a great influence on the spectral characteristics and intensity of ground motions. The modified Matasovic model is accepted to well characterize the nonlinear behavior of soil. The profile soil models of 50 boreholes for the quaternary deep sediment layers are established for site seismic response based on software DeepSoil. The predominant period Tp, average spectral period Tavg of the acceleration response spectrum and the mean period Tm of the Fourier amplitude spectrum of an acceleration time history are employed as the proxy to characterize the spectral characteristics of surface ground motions. The ground motion intensity is characterized by the Arias strength Ia and the peak ground acceleration (PGA). The results show that: (1) Tp doesn't characterize the changes of seismic motions spectral characteristics during the seismic wave propagating from bedrock to surface ground. Tavg and Tm have a good similarity in characterizing the spectral characteristics of seismic motions. (2) When the seismic bedrock motions are rich for high frequency components, Tavg and Tm show a linear growth trend with increasing peak bedrock acceleration. However, there are inflection points in the growth trend lines of Tavg and Tm if the seismic bedrock motions are rich in low frequency components. (3) The nonlinear generation rates of PGAs and Ia with increasing peak bedrock acceleration are essentially consistent, and the values of PGAs and Ia show much greater dispersion with increasing peak bedrock accelerations.