A new class of multilayered, viscoelastic Earth models based on PREM, with an incompressible, linear, viscoelastic Maxwell rheology, is applied to the modeling of co-seismic and post-seismic deformation following large earthquakes. The novelty of our approach stands on the usage, for the first time in post-seismic studies, of a fully analytical scheme based on normal mode theory that allows to deal with some of the complexities of the real Earth, such as lithospheric and mantle layering, sphericity and self-gravitation. For a dip-slip source, used as a test case, elastic layering of the lithosphere is necessary for the modeling of realistic patterns of post-seismic deformation, although only a few layers, namely three, are sufficient to reproduce correct deformation patterns, in consequence of the fact that below the crust, the lithosphere inferred from PREM is rather homogeneous. The viscosity structure of the mantle has a major influence on post-seismic deformation in the far field, at distances from the epicenter of the order of 100 km. At least for lithospheric sources, precise modeling of post-seismic deformation does not require for the mantle the same fineness of layering that is necessary for the lithosphere. Our findings are key for future analyses of the co-seismic and post-seismic effects of large earthquakes, in view of a correct interpretation of VLBI, GPS and Satellite Differential Radar Altimetry data.

The role played by transient rheology in the interpretation of mantle viscosity is re-examined. This investigation has been carried out by comparing the amplitude responses with the data of secular variation of Jdot 2, the relative sea-level histories at sites well within the ice margins and at the ice margin like the city of Boston. A linear Burgers' body rheology as been assumed in the lower mantle. The data near the edge of the ice load proves most sensitive to the transient viscosity structure. The non-monotonic behavior of sea-level data near Boston can be explained both by a steady-state lower mantle viscosity of 10 22P with a thick lithosphere and also by a transient lower mantle rheology but with a thin lithosphere

Gives a theoretical development of a uniformly valid solution for describing the polar motions of a layered viscoelastic Earth. Such solutions require the usage of two classes of eigenspectra to describe the processes of rotational deformation and viscous relaxation. One set consisting of real eigenvalue describes the isostatic relaxation of the mantle by viscous creep. The second one governs the readjustment of the rotational axis of the viscoelastic Earth, and the eigenspectrum is complex valued. These solutions are capable of describing rotational phenomena ranging from Chandler wobble excitation to long-term polar drift. A comparative study is conducted between the complete solution for polar wander and one in which a number of the rotational modes has been truncated

From the analysis of sea-level data near the centre of the former Fennoscandian ice sheet and the theoretical predictions of vertically and laterally stratified Earth models, the authors explore the extent to which lateral viscosity variations could have influenced the estimate of long term mantle viscosity. A finite element scheme in cylindrical symmetry was followed focusing on the effects of lateral viscosity contrasts of different magnitudes and wavelengths. Sea-levels are consistent with long wavelength lateral viscosity contrasts of at most 2 orders of magnitude; short wavelength variations, comparable with the lateral extension of the surface load, should be ruled out. Differences in the average viscosities inferred from laterally stratified and uniform mantle models, may be as high as 1 order of magnitude

Long wavelength time variations of the gravity field detected by means of laser tracking of geodetic satellites provide nowadays the unique opportunity to infer simultaneously the upper and lower mantle viscosity and the mass imbalance between ice accumulation and loss in Antarctica and Greenland. Here we show that mantle viscosity inversion based on stratified viscoelastic Earth models of the Pleistocene deglaciation, on two independent Satellite Laser Ranging (SLR) solutions for the even and odd zonal components of the geopotential and on True Polar Wander (TPW), indicate that present day ice mass loss in Antarctica amounts to about -250 Gt/yr , equivalent to a global sea level rise of 0.7 mm/yr, and that the lower mantle is more viscous than the upper mantle. The odd zonals of the two SLR solutions and TPW indicate two admissible upper mantle viscosities, close to 10 20 Pa s and to 10 21 Pa s respectively