AUTOMATED SOURCE-EDGE LOCATION WITH A NEW VARIABLE PASS-BAND HORIZONTAL-GRADIENT OPERATOR

A new class of space-domain convolution operators permits computation of the components of the horizontal gradient of gridded potential-fiel d data. These so-called gradient-component operators allow one to vary the passband and thus control the frequency content of the resulting horizontal-gradient map. This facilitates computation of gradient maps that accommodate data of widely varying frequency content. Examinatio n of the transfer functions of these operators suggests that this meth od of numerical differentiation is well suited to potential-field data : in particular, the operators suppress tong wavelengths and high-freq uency noise bands and amplify signal. Maps of the horizontal gradient of certain potential fields (e.g., gravity, pseudogravity) may be comb ined with algorithms that locate relative maxima, so-called thresholdi ng, to automate the procedure of source-body edge detection, which is a useful tool in mapping, for example, basement grain, fault patterns, and igneous intrusive bodies. We apply this new operator, together wi th an existing thresholding algorithm, to a field example from western Canada and demonstrate its potential for improved imaging of the hori zontal-gradient magnitude and thus improved edge detection.