Geoid heights and lithospheric stresses for a dynamic Earth
Résumé
Mass heterogeneities in the Earth's crust and mantle are known to exist at all depths and for a large range of wavelengths characteristic of their lateral extent. They are the sources of measurable quantities like topography, tectonic stresses and the geoid. Quantitative relationships between these surface observables and deep sources are established for various Earth viscosity structures with spherical symmetry. For an homogeneous mantle, the surface stresses and the geoid height increase with the depth of the perturbing heterogeneity but decrease markedly beyond a critical depth proportional to the wavelength. It is shown that upper mantle return flow is also capable of generating the geoid without producing too large a topography and too strong tectonic stresses. The two types of contribution are expected to occur in the Earth. Further progress will require careful data analysis and correlation between topography, stresses, geoid and deep density structures. -from Authors