The scattering of seismic waves from saturated river valley with water layer: Modelled by indirect boundary element method.

• In this paper, an indirect boundary element method (IBEM) is proposed to solve the problem of seismic wave scattering in saturated river valley with water layer. • In this paper, the law of seismic wave scattering by saturated river valleys with overlying fluid layers is revealed. • The quantitative evaluation of the seismic field near the river valley is carried out, which is helpful to improve the reliability of the seismic design of such sites. River valley topography will cause local amplification effect and significant spatial variation effect of ground motion. In this paper, an indirect boundary element method (IBEM) is proposed to solve seismic wave scattering in sedimentary valleys. A ''water layer - soft sedimentary layer - poroelastic halfspace'' model is established, and the effects of water layer, soil parameters of sedimentary layer and terrain on incident P and SV waves are discussed in detail. The numerical results demonstrate that the scattering characteristics are closely related to the depth of water layer, porosity, the location of observation points, et al. The surface displacement amplitude decreases with increasing water layer thickness, with a maximum reduction of 16.2%. Moreover, the peak ground acceleration (PGA) is significantly larger and the seismic response is stronger when the observation point is located outside the valley compared to the observation point inside the valley. The influence of porosity on Fourier spectrum and response spectrum curve is mainly reflected in the peak value and predominant frequency. The research results can provide a theoretical basis for the seismic fortification of the structures around the saturated sedimentary valley. [ABSTRACT FROM AUTHOR]