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Flattening of the Earth: further from hydrostaticity than previously estimated

Abstract : The knowledge of the gravitational potential coefficients J2 and J4 of a hydrostatic Earth model is necessary to deal with non-hydrostatic properties of our planet. They are indeed fundamental parameters when modelling the 3-D density structure or the rotational behaviour of our planet. The most widely used values computed by Nakiboglu need to be updated for two reasons. First, we have noted a mistake in one of his formulae. Secondly, the value of the inertia ratio I/MR2 chosen at the time of PREM is not any more the best estimate. Both corrections slightly but significantly reduce the hydrostatic J2 value: the dynamical flattening of the Earth is even further from hydrostaticity than previously thought. The difference between the polar and equatorial radii appears to be 113 +/- 1 m (instead of 98 m) larger than the hydrostatic value. Moreover, uncertainties upon the hydrostatic parameters are estimated.
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F. Chambat, Y. Ricard, B. Valette. Flattening of the Earth: further from hydrostaticity than previously estimated. Geophysical Journal International, Oxford University Press (OUP), 2010, 183, pp.727-732. ⟨10.1111/J.1365-246X.2010.04771.X⟩. ⟨insu-00564808⟩



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