Direct interpretation methods in applied geophysics

Abstract

In contrast to the use of master curves and other trial-and-error processes, the direct methods of interpreting geophysical data are based on computational procedures which yield the unknowns in a more direct way. The present paper emphasizes the usefulness of these methods, and it is shown that they are closely related to the methods of electrical network synthesis. The driving point exploration and synthesis of linear lumped parameter ladders on the basis of continued fraction expansions is shown in some detail. An analogous procedure is applied to systems with distributed parameters. It is shown that the interpretation of D.C. conduction data obtained in the case of a horizontally stratified earth is equivalent to the driving point synthesis of an elastic bar composed of homogeneous sections and capable of longitudinal displacements. Similarly, the interpretation of magneto-telluric data is equivalent to the driving point synthesis of an electric line composed of sections with constant specific inductance and specific resistance. Formal solutions of the synthesis problems involved are given, and further geophysical cases are discussed.