A numerical method is presented for computing ground surface displacement induced by a vertical point force acting on a three-dimensional layered elastic half-space. The contribution of the residue of the Rayleigh poles and the branch line integrals, i.e., that of Rayleigh and body waves, to the ground displacement is computed for a two-layered medium, and its variation with the S-wave velocity ratio between the surface and base layers, V_<S2>/V_<S1>, is examined. It is shown that, when V_<S2>/V_<S1> is less than 1.5 or when V_<S2>/V_<S1> is greater than 1.5 and the normalized frequency is not close to 1, Rayleigh waves get to dominate as the normalized ditance is greater than at most 3〜4. When V_<S2>/V_<S1> is greater than 3 and the normalized frequency is close to 1, body waves dominate up to a normalized distance of 100, due to their peculiar attenuation characteristics which are very similar to those of Rayleigh waves.
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