Effects of spatial soil variability in 2D ground response models of Wellington

Current analytical techniques for seismic ground response analysis are largely based on 1D wave propagation assumptions, while the growing body of evidence indicates that 1D analysis is only appropriate at a minority of sites. The limitations of 1D analysis come from mechanisms related to how the site is modelled, e.g. wave scattering from small-scale soil heterogeneity cannot be captured, and how the site is defined, e.g. no consideration for basin edge effects or 2D/3D geometry. This paper investigates how consideration for some of these missing factors affects the surficial site amplification for a strong motion recording site in Wellington, New Zealand. Plane strain analyses of the surficial soils and underlying basin materials and geometry are conducted with consideration for the spatial variability of the surficial soils across the model through random variations of an underlying simplified profile. The differences in results between this approach and 1D wave propagation methods are discussed and assessed