Abstract: The scattering and diffraction of plane Rayleigh waves in acircular-arc layered alluvial valley with soft-soil deposits is studiedanalytically in this paper. The soft sediments in the circular-arc valleyare simulated by applying Biot's dynamic theory to a saturated porous medium, andthe half-space is assumed as an elastic single-phase medium. In this analysis,Fourier-Bessel series expansion technique is employed to obtain theanalytical solutions. Based on the analytical solutions, the effects ofdimensionless frequency, the layered sediments sequence and the relativerigidity and thickness on the scattering and diffraction are investigated.