On One Peculiarity of Calculation of Oceanic Gravimetric Effect

Abstract

The data of modern ground-based and satellite gravity measurements currently play an important role in the studies of the Earth’s structure and resonance effects as well as in mineral prospecting. At the same time, adequate inferences from these observations can only be made provided correct processing and interpretation of the data which avoids misleading conclusions in these fields of research. In the diurnal and semidiurnal range of tidal waves, one of the most important factors is the oceanic gravimetric effect which substantially alters the parameters of the solid Earth’s tides even in the most distant regions from the coastline. The key attention in this paper is focused on the calculation of direct Newtonian attraction of water masses. It is shown that from the standpoint of physics and the closeness of the calculated results to the observations, the most correct method for calculating this effect is to take direct derivative of the potential of water masses or, which is the same, to sum up vertical components of accelerations created by each elementary area of sea surface at the observation point. The latter is fully consistent with the ideas suggested by B.P. Pertsev on this subject. In other words, in this work it is shown that a correct formula for the generalized gravimetric factor describing the sum of the attraction and oceanic loading effect is $$ - \frac{1}{2} + 2h{\kern 1pt} '\,\, - (n + 1)k{\kern 1pt} '$$ rather than $$n + 2h{\kern 1pt} '\,\, - (n + 1)k{\kern 1pt} '$$ which is assumed in the vast majority of works of other authors (here, $$h{\kern 1pt} '$$ and $$k{\kern 1pt} '$$ are the load Love numbers). The standpoint presented in this paper is proved both theoretically and by the comparison of calculations with the observations by the network superconducting gravimeters of the Global Geodynamic Project. In particular, it is found out that the calculation results obtained in this paper are at least double as close to the observations as those provided by the most commonly cited methods of the other authors. It is concluded that the accuracy of calculation of the oceanic gravimetric effect is as of now insufficient for refining the resonance curve based on gravimetric data.