On selecting the excess density in gravity modeling of inhomogeneous media

In this paper, a relatively simple and physically solid algorithm is developed for solving the problem of reference density selection for the models of heterogeneous media. The way is suggested for determining the excess density of the individual elements of the structured model against the background varying density of the hosting rocks: in the calculations, the latter should be replaced by the hydrostatic density of the normal model, which only depends on depths. It is shown that the excess density of the elements within the inhomogeneous layer, referred to the depth-varying hydrostatic density of the normal model, has a significantly lower value throughout the entire depth of the studied domain and minimizes the gravitational effect of density contact along a curvilinear boundary. The efficiency of the algorithm is demonstrated by the model example and case study. Within the density model for the lithosphere of the Timan–Pechora plate, the structural layers corresponding to the sedimentary cover, crystalline crust, and upper mantle are isolated. For each of them, the fields are calculated within the gravitational model of a heterogeneous layer with curvilinear boundaries.