Electromagnetic methods in applied geophysics - applications. Part A and part B / Электромагнитные методы в прикладной геофизике - приложения A и B

Electromagnetic Methods in Applied Geophysics, Volume I, Theory presented the mathematical and physical foundations common to all EM methods. The purpose of Volume I was to help facilitate the understanding of the theory involved and to provide a limited amount of interpretational aids. Volume H, Applications is devoted to a method-by-method treatment of the principal EM techniques in common use. The first chapter gives a unified treatment of the physical basis of EM methods of exploration and is followed by a comprehensive chapter on the magnetometric resistivity method (MMR). The inclusion of MMR, essentially a dc technique, in an EM volume might seem puzzling at first. However, an increased understanding of current channeling (current gathering, galvanic) effects indicates that anomalies attributable to current channeling can be interpreted best using MMR concepts. In many instances, EM induction plays only a small part in the observed anomaly which is predominantly attributable to current channeling. A case in point is the VLF technique. Not long ago all interpretation was done using only EM induction concepts. Today, some geophysicists describe VLF as "MMR with phase", a tacit acknowledgment of the important role played by current channeling effects in observed VLF anomalies. <...>