INTERNAL LOADING OF A COMPRESSIBLE EARTH - EFFECT OF A SOLID LITHOSPHERE

This paper shows the importance of including a lithosphere in the Eart h model when inferring a mantle viscosity profile or density-velocity conversion factor from mantle circulation. The free-slip and no-slip c onditions are investigated at the mantle-lithosphere boundary. Results obtained for Earth models that include a lithosphere are compared wit h those obtained for models where no lithosphere is considered. In par ticular, it is shown that models without a lithosphere are inconsisten t with the no-slip condition at the mantle-lithosphere interface, beca use they introduce a tangential stress discontinuity at that level. Wi th regard to the estimations of the mantle viscosity profile from the comparison between observed and computed geoids and plate velocities, the principal results obtained previously using the no-slip condition without a lithosphere (i.e. the best fit is obtained for a one-cell co nvection with a large viscosity jump at a depth of 670 km) are still v alid. Nevertheless, to infer a precise viscosity profile or density-ve locity conversion factor when using the no-slip condition, a lithosphe re must be accounted for, because the results are different for models with and without a lithosphere. (C) 1997 Published by Elsevier Scienc e B.V.