The Effect of Mantle Inelasticity On Tidal Gravity: A Comparison Between the Spherical and the Elliptical Earth Model

Abstract

The effects of mantle inelasticity on the Earth gravity response to the luni-solar attraction has been computed for the two most commonly used Earth models: a spherical non-rotating Earth and an elliptical uniformly rotating Earth. the corresponding results are compared in this paper. We conclude that the effects of mantle inelasticity on the amplitude of the gravimetric factor are less than 0.1 per cent for the non-zonal tides and that the effect on the tidal gravity phase is of the order of -0.005° for frequencies between the semi-diurnal and the monthly tides. These results are obtained by directly integrating the equations of motion within the Earth interior. In the spherical case they are independently verified by introducing a new method that makes use of the causality principle. Whereas the effect of mantle inelasticity on tidal gravity appears to be too small to be measured, its effect on the Chandler wobble period is significant and results in a lengthening of about 10 days.