Dictionary:Magnetic interpretation methods
The objective of magnetic data interpretation usually is to locate anomalous magnetic material, its depth, dimensions, and magnetization. Most hydrocarbon exploration uses of aeromagnetics involves determining the depth to the top of anomalous bodies (and thereby inferring the depth to magnetic basement) and the preparation of a contour map of the magnetic basement from the results. Inverse solutions involve various auxiliary conditions to achieve a solution. Various shape measurements are made on magnetic profiles or maps and used in conjunction with depth rules (q.v.). Two-dimensional convolution operations such as calculation of a second-vertical-derivative map, downward continuation, or reduction to the pole sometimes are used to help locate anomalous bodies and determine their shapes. Sometimes interpretation involves comparison with the fields over known areas or comparison against the fields of model anomalies shown in a catalog of master curves. The most common magnetic interpretation models are a dipping-dike and vertical prism for intrabasement bodies and a thin magnetic layer for structural features. Iterative methods involve calculating the field that a model would produce, comparing it with the observed field, and then iterating until a satisfactory degree of fit between model field and observed field is achieved. Sedimentary anomalies are also interpreted, especially with high-resolution data in areas of deep basement. See also automated depth estimation.