Inverse model approach for vertical load deformations in consideration of crustal inhomogeneities

Mass redistributions in various components of the Earth system exert time-variable surface loads on the solid Earth. The resulting variations of the Earth's geometry are reflected by vertical and horizontal displacements of geodetic markers. Usually the effect of loading on crustal deformation is computed by means of a weighting function which is based on site-independent load Love numbers (Green's function). But as the Earth's crust is composed of heterogeneous material, the adequateness of a site-independent approach deserves a review. We propose a procedure for the computation of vertical crustal deformations in which the Green's function is substituted by a site-dependent exponential function. Its parameters are estimated by means of least-squares adjustment using time series of globally distributed GPS sites. On the basis of the crustal model Crust2.0 regions are predefined for which identical parameters are determined. Pressure fields of atmosphere, continentalhydrosphere and oceans are considered as forcing. In order to validate the numerical results, model time series from both the traditional and the site-dependent approach are compared with GPS observations. Explicit improvement is achieved in regions which are covered well with observations and feature strong pressure variability. However in regions like Africa and Antarctica parameter estimation is difficult due to the sparse distribution of GPS sites.