On: “Gravity Interpretation using the Fourier Integral” by J. W. Berg, Jr., and M. E. Odegard (GEOPHYSICS, vol. 30, no. 3, p. 424–438, June 1965)
The authors do not state explicitly that equations (1) and (12) express gravity anomalies of the two‐dimensional cylinder and fault respectively. These structures have an infinite extension along the strike, and all the gravity profiles perpendicular to the strike are identical. For this reason it is admissible to apply the one‐dimensional Fourier transform to obtain the one‐dimensional amplitude spectra shown in Figures (1) and (5). The situation, however, is different for the sphere, which does not have a one‐dimensional gravity profile in the above sense, but rather a two‐dimensional field with cylindrical symmetry. Instead of using the one‐dimensional Fourier transform as given by (6) along a straight line, we must apply the two‐dimensional Fourier transform over the whole area. Because of the circular symmetry, one radial variable will suffice in place of the two Cartesian coordinates x and y, and the two‐dimensional Fourier transform can be expressed as Hankel transform, so that equation (6) becomes [Formula: see text]