Electromagnetic fields migration method

The properties of the reversed continuation of the electromagnetic field and the possibility of using electromagnetic migration for solving inverse problems in geoelectrics are examined. The following topics are discussed: integral Stratton-Chu formulas for nonstationary field; integrals of the Stratton-Chu type for a nonstationary field; reversed continuation of nonstationary electromagnetic fields; electromagnetic field migration; pseudo-migration fields; properties of electromagnetic migration; and migration of model electromagnetic fields. The theoretical and experimental materials given show that electromagnetic field migration can be used effectively in solving the geoelectric problem, making it possible to retrieve the geoelectric image of the medium. It is demonstrated that procedures involved in migration of the nonstationary electromagnetic field correctly conform to Tikhonov principles; the method is valid for nonstationary fields of both artificial and natural origin; and in pin-pointing a deep inhomogeneity and determining its configuration, it is necessary to have information only on the electromagnetic field observed at the earth's surface and on the conductivity of a normal section.