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Abstract:
Gravity measurements on the surface of the Earth reflect the combined effect of deeper and longer wavelength (regional) as well as shallower and short wavelength (residual) geological features. Large-scale Bouguer gravity anomalies have often been used to probe into mass/density variations in the Earth’s deep interior. However, for a limited regional survey, there is a need to discriminate the regional and residual mass anomalies separately for modeling purposes. For this, both graphical as well as analytical methods have been used over the decades. However, most of these techniques failed to be completely objective, since there was a need to choose the appropriate frequency range in frequency filtering, the degree of the polynomial in polynomial fitting, and the choice of height in upward continuation, etc. Therefore, we developed a new analytical method, based on Finite Element Approach (FEM), which effectively computes the regional and residual gravity components, and admiringly fills the long-standing gap. In addition, this method also computes the isostatic anomaly, without explicitly invoking any isostatic model – Airy-Heiskanen, Pratt-Hayford, or Vening-Meinsz; thereby eliminating the numerous assumptions, and with that overcoming to a great degree the inherent inaccuracies and the ambiguities. This method has been found to be very effective in studying the geological evolution of geodynamically complex regions.
