Chapter 5 3-D EM Forward Modeling Using Balance Technique

Abstract

This chapter focuses on the balance technique for the forward modeling of electromagnetic fields in 3-D media. The chapter reviews numerical and analog approaches to the forward problem solution. Numerical methods, in turn, are subdivided into two large groups: Integral equation methods and differential equation methods. A comparative analysis of these two groups of methods and hybrid approaches based on their combination is also presented in the chapter. Parallel to the method of volume integral equations (VIE) that involves integration over the entire volume of the anomalous domain, a method of surface integral equations (SIE) implying integration only over the boundary of the domain, has been developed. Analysis and interpretation of electromagnetic field anomalies on the Earth, investigation of the resolution of soundings as well as a number of other methodological problems encountered today in electromagnetics require calculation of many different models. Advances in geoelectrics call forth computing 3-D electromagnetic fields in complicated situations when the inhomogeneity exhibits an arbitrary shape and dimension and the anomalous electric conductivity in the model varies arbitrarily—for example, in regional models.