3-D INVERSION OF GRAVITY-DATA

We present two methods for inverting surface gravity data to recover a 3-D distribution of density contrast, In the first method, we transfo rm the gravity data into pseudomagnetic data via Poisson's relation an d carry out the inversion using a 3-D magnetic inversion algorithm. In the second, we invert the gravity data directly to recover a minimum structure model, In both approaches, the earth is modeled by using a l arge number of rectangular cells of constant density, and the final de nsity distribution is obtained by minimizing a model objective functio n subject to fitting the observed data. The model objective function h as the flexibility to incorporate prior information and thus the const ructed model not only fits the data but also agrees with additional ge ophysical and geological constraints. We apply a depth weighting in th e objective function to counteract the natural decay of the kernels so that the inversion yields depth information. Applications of the algo rithms to synthetic and field data produce density models representati ve of true structures. Our results have shown that the inversion of gr avity data with a properly designed objective function can yield geolo gically meaningful information.