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

So far, interpretations of postglacial rebound have usually been based on t he assumption of laterally homogeneous earth models. However, in view of th e increasing evidence of the 3-D structure of the Earth's mantle, several s tudies 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 incompre ssible and vertically homogeneous flat earth models with lateral variations of the shear modulus and viscosity. The solution is obtained using a pertu rbation method and given in analytical form. Our results show that sinusoid al variations of the parameters of less than one order of magnitude can mod ify the vertical surface displacement associated with a model of the Fennos candian ice sheet by several tens of metres. The modifications increase app roximately in proportion to the amplitude of the lateral variations. The ov erall increase of the modifications with increasing wavelength is complicat ed in detail and also results in changes of the spatial and temporal distri butions of the vertical surface displacement.