Effects of lateral viscosity variations on postglacial rebound: An analytical approach

So far, interpretations of postglacial rebound have usually been based on the assumption of laterally homogeneous earth models. However, in view of the increasing evidence of the 3-D structure of the Earth's mantle, several studies on the effects of lateral variations of the viscosity on postglacial rebound have been completed during the last decade. In the present study, we consider load-induced viscoelastic and viscous perturbations of incompressible and vertically homogeneous flat earth models with lateral variations of the shear modulus and viscosity. The solution is obtained using a perturbation method and given in analytical form. Our results show that sinusoidal variations of the parameters of less than one order of magnitude can modify the vertical surface displacement associated with a model of the Fennoscandian ice sheet by several tens of metres. The modifications increase approximately in proportion to the amplitude of the lateral variations. The overall increase of the modifications with increasing wavelength is complicated in detail and also results in changes of the spatial and temporal distributions of the vertical surface displacement.