Abstract:The influence of wavelength and Fourier amplitude spectra of the body wave (P and SV wave), together with its interference surface waves (Rayleigh wave) on the the rocking components of earthquake motions was explored, and the synthetic formula of rocking components of earthquake motions was obtained. The dispersion curve of surface wave in given crustal model was obtained based on the elasticwavetheory and the fast δmatrix algorithm. Meanwhile the synthetic process of the rocking components of earthquake motions involving incident body and surface waves was explored based on Trifunac’s research. The Trifunac’s composite formula was modified to generate translational components of earthquake motions, relevant to earthquake magnitude M, epicentral distance R, and site condition s. Then rocking components of earthquake motions of a spot of ground surface were generated according to the differential frequency of body and surface waves, and corresponding tripartite response spectrum was given.