3D correlation imaging of magnetic total field anomaly and its vertical gradient

We present a new 3D correlation imaging approach for magnetic total field anomaly and its vertical gradient for deriving a 3D equivalent magnetic dipole distribution in the subsurface. In this approach, we divide the subsurface space into a 3D regular grid, and then at each grid node calculate cross correlation between the observed magnetic total field anomaly (or its vertical gradient) and the theoretical magnetic total field anomaly (or its vertical gradient) due to a magnetic dipole. The resultant correlation coefficients are used to describe the equivalent magnetic dipoles distribution in a probabilistic sense. The approach was tested both on the synthetic magnetic data of a model of multiple rectangular prisms and on the real aeromagnetic data from an iron-ore deposit area in the middle–lower reaches of the Yangtze River, China. The results show that the equivalent magnetic dipole distribution derived by the approach basically reflects the subsurface magnetic sources and also illustrate that the approach for the vertical gradient produces a higher resolution of the equivalent magnetic source distribution than that for magnetic total field anomaly alone.