In this paper, three-dimensional scattering of plane harmonic SH, SV and P waves by alluvial valleys is investigated by using a boundary element method in frequency domain. It is shown that in order to achieve real responses, problem must be analyzed and modeled three-dimensionally. Also, for exact evaluation of surface ground motions in alluvial valleys all key parameters such as layering shape, material and geometrical characteristics, wave type, angle and azimuth of incidence, reflection and refraction effects must be taken in to account altogether.
The accuracy and efficiency of the proposed formulations for the computation of surface displacement field amplification are demonstrated by solving a number of problems.