Three-dimensional correlation imaging for total amplitude magnetic anomaly and normalized source strength in the presence of strong remanent magnetization

We present the 3D correlation imaging approach for the total magnitude magnetic anomaly and the normalized source strength data for reducing effects of strong remanent magnetization. We divide the subsurface space into a 3D regular grid and then calculate the cross correlation between the observed total magnitude magnetic anomaly or normalized source strength and the theoretical total magnitude magnetic anomaly or normalized source strength at each grid node due to a magnetic dipole. The resultant correlation coefficients are used to describe the equivalent magnetic dipole distribution underground in a probabilistic sense. The two approaches were tested both on the synthetic magnetic data and the real magnetic data from a metallic deposit area in the middle-lower reaches of the Yangtze River, China. The results show that the two approaches can considerably reduce effects of remanent magnetization and delineate magnetic sources in the subsurface, and that the approach for the normalized source strength is less sensitive to strong remanent magnetization than that of the total magnitude magnetic anomaly.