The location of spherical cavities using a tripotential resistivity technique

The surface gravitational and magnetic field anomalies due to a contrasting spherical body at depth are well known and appear in geophysical textbooks. The corresponding problem of the anomaly in apparent resistivity arising from such a body, owing to its conductivity contrast, is less frequently referred to because of the lengthy potential solutions involved. In electrical interpretation, few potential solutions exist for buried bodies of limited three‐dimensional extent, and consequently the simplest of these problems, the buried sphere, has received particular attention. Following early work by Hummel (1928), Webb (1931) produced potential solutions for this problem, and more recently Lipskaya (1949) has derived solutions and computed extensive numerical results. For the particular case of an infinitely conducting sphere, Van Nostrand (1953) has computed comprehensive numerical solutions, and more recently Van Nostrand and Cook (1966) presented a very detailed account of work on the buried sphere.