POTENTIAL-FIELD INVERSION -- SUPPORTING THE CONSTRUCTION AND TESTING OF GEOLOGIC MODELS

The inversion of potential-field (gravity and magnetic anomaly) data can provide useful information for developing or testing geologic models in two or three dimensions. This information can include the locations of geologic contacts or faults, often with estimates of dip, strike, and physical property contrast; the depth to basement rocks or the thickness of basin sediments; the extent of buried volcanic rocks; and the lithology of the basement. Practical approaches to potential-field inversion include iterative inversion using forward modeling with independent constraints, direct inversion using the conjugate gradient method, and methods that estimate the parameters of simple sources. The results of inversion vary by approach from surfaces representing geologic interfaces, to images of subsurface density or magnetization, to locations and characteristics of physical-property edges. Each of these results can be incorporated into geologic models, or can be used to test existing models for agreement with the observed gravity and magnetic anomaly data.