Automatic DEXP Imaging of Potential Fields Independent of the Structural Index

A new imaging method is developed to estimate the depth to the sources of potential fields, independent of the structural index. The method consists of applying the Depth from Extreme Point (DEXP) method to the ratio between two different-order partial derivatives of the field. We show that the scaling function of this ratio does in fact not depend on the structural index but only on the difference between the two orders of differentiation used. The scaling exponent, needed to perform the DEXP transformation, is then automatically determined. The depth to the sources is simply estimated from the extreme points of the DEXP image, which is obtained in a automatic way. The structural index can also be determined. The method is tested with synthetic examples and shows a good agreement with true values of the source parameters. The method was also applied to a real data of a vertical magnetic anomaly from the Pima copper mine, Arizona, USA. The results are consistent with the known information about the causative source.