Computational Methods In Geophysical Electromagnetics

This monograph provides a framework for students and practitioners who are working on the solution of electromagnetic imaging in geophysics. Bridging the gap between theory and practical applied material (for example, inverse and forward problems), it provides a simple explanation of finite volume discretization, basic concepts in solving inverse problems through optimization, a summary of applied electromagnetics methods, and MATLAB??code for efficient computation.

This monograph provides a framework for students and practitioners who are working on the solution of electromagnetic imaging in geophysics. Bridging the gap between theory and practical applied material (for example, inverse and forward problems), it provides a simple explanation of finite volume discretization, basic concepts in solving inverse problems through optimization, a summary of applied electromagnetics methods, and MATLAB??code for efficient computation.

Computational Geo-Electromagnetics: Methods, Models, and Forecasts, Volume Five in the Computational Geophysics series, is devoted to techniques for building of geoelectrical models from electromagnetic data, featuring Bayesian statistical analysis and neural network algorithms. These models are applied to studying the geoelectrical structure of famous volcanoes (i.e., Vesuvio, Kilauea, Elbrus, Komagatake, Hengill) and geothermal zones (i.e., Travale, Italy; Soultz-sous-Forets, Elsace). Methodological recommendations are given on electromagnetic sounding of faults as well as geothermal and hydrocarbon reservoirs. Techniques for forecasting of petrophysical properties from the electrical resistivity as proxy parameter are also considered. Computational Geo-Electromagnetics: Methods, Models, and Forecasts offers techniques and algorithms for building geoelectrical models under conditions of rare or irregularly distributed EM data and/or lack of prior geological and geophysical information. This volume also includes methodological guidelines on interpretation of electromagnetic sounding data depending on goals of the study. Finally, it details computational algorithms for using electrical resistivity for properties beyond boreholes. Provides algorithms for inversion of incomplete, rare or irregularly distributed EM data Features methodological issues of building geoelectrical models Offers techniques for retrieving petrophysical properties from EM sounding data and well logs

In this book the author presents the state-of-the-art electromagnetic (EM)theories and methods employed in EM geophysical exploration.The book brings together the fundamental theory of EM fields and the practicalaspects of EM exploration for mineral and energy resources.This text is unique in its breadth and completeness in providing anoverview of EM geophysical exploration technology. The book is divided into four parts covering the foundations of EMfield theory and its applications, and emerging geophysical methods.Part I is an introduction to the field theory required for baselineunderstanding. Part II is an overview of all the basic elements ofgeophysical EM theory, from Maxwell's fundamental equations to modernmethods of modeling the EM field in complex 3-D geoelectrical formations. Part III deals with the regularized solution of ill-posedinverse electromagnetic problems, the multidimensional migration and imaging ofelectromagnetic data, and general interpretation techniques. Part IV describes major geophysical electromagnetic methods—direct current (DC), induced polarization (IP), magnetotelluric(MT), and controlled-source electromagnetic (CSEM) methods—and covers different applications of EM methods in exploration geophysics, includingminerals and HC exploration, environmental study, and crustal study. Presents theoretical and methodological findings, as well as examples of applications of recently developed algorithms and software in solving practical problems Describes the practical importance of electromagnetic data through enabling discussions on a construction of a closed technological cycle, processing, analysis and three-dimensional interpretation Updates current findings in the field, especially with MT, magnetovariational and seismo-electrical methods and the practice of 3D interpretations

Presents current research into electromagnetic computationtheories with particular emphasis on Finite-Difference Time-DomainMethod This book is the first to consolidate current research and toexamine the theories of electromagnetic computation methods inrelation to lightning surge protection. The authors introduceand compare existing electromagnetic computation methods such asthe method of moments (MOM), the partial element equivalent circuit(PEEC), the finite element method (FEM), the transmission-linemodeling (TLM) method, and the finite-difference time-domain (FDTD)method. The application of FDTD method to lightningprotection studies is a topic that has matured through manypractical applications in the past decade, and the authors explainthe derivation of Maxwell’s equations required by the FDTD,and modeling of various electrical components needed in computinglightning electromagnetic fields and surges with the FDTDmethod. The book describes the application of FDTDmethod to current and emerging problems of lightning surgeprotection of continuously more complex installations, particularlyin critical infrastructures of energy and information, such asoverhead power lines, air-insulated sub-stations, wind turbinegenerator towers and telecommunication towers. Both authors are internationally recognized experts in the areaof lightning study and this is the first book to present currentresearch in lightning surge protection Examines in detail why lightning surges occur and what can bedone to protect against them Includes theories of electromagnetic computation methods andmany examples of their application Accompanied by a sample printed program based on thefinite-difference time-domain (FDTD) method written in C++program

In this work, an iterative approach using the finite difference frequency domain method is presented to solve the problem of scattering from large-scale electromagnetic structures. The idea of the proposed iterative approach is to divide one computational domain into smaller subregions and solve each subregion separately. Then the subregion solutions are combined iteratively to obtain a solution for the complete domain. As a result, a considerable reduction in the computation time and memory is achieved. This procedure is referred to as the iterative multiregion (IMR) technique. Different enhancement procedures are investigated and introduced toward the construction of this technique. These procedures are the following: 1) a hybrid technique combining the IMR technique and a method of moment technique is found to be efficient in producing accurate results with a remarkable computer memory saving; 2) the IMR technique is implemented on a parallel platform that led to a tremendous computational time saving; 3) together, the multigrid technique and the incomplete lower and upper preconditioner are used with the IMR technique to speed up the convergence rate of the final solution, which reduces the total computational time. Thus, the proposed iterative technique, in conjunction with the enhancement procedures, introduces a novel approach to solving large open-boundary electromagnetic problems including unconnected objects in an efficient and robust way. Contents: Basics of the FDFD Method / IMR Technique for Large-Scale Electromagnetic Scattering Problems: 3D Case / IMR Technique for Large-Scale Electromagnetic Scattering Problems: 2D Case / The IMR Algorithm Using a Hybrid FDFD and Method of Moments Technique / Parallelization of the Iterative Multiregion Technique / Combined Multigrid Technique and IMR Algorithm / Concluding Remarks / Appendices

This book is an indispensable resource for making efficient and accurate formulations for electromagnetics applications and their numerical treatment, Employing a unified and coherent approach that is unmatched in the field, the authors deatil both integral and differential equations using the method-of-moments and finite-element procedures.

This volume will define the direction of eddy-current technology in nondestructive evaluation (NDE) in the twenty-first century. It describes the natural marriage of the computer to eddy-current NDE, and its publication was encouraged by favorable responses from workers in the nuclear-power and aerospace industries. It will be used by advanced students and practitioners in the fields of computational electromagnetics, electromagnetic inverse-scattering theory, nondestructive evaluation, materials evaluation and biomedical imaging, among others, and will be based on our experience in applying the subject of computational electromagnetics to these areas, as manifested by our recent research and publications. Finally, it will be a reference to future monographs on advanced NDE that are being contemplated by our colleagues and others. Its importance lies in the fact that it will be the first book to show that advanced computational methods can be used to solve practical, but difficult, problems in eddy-current NDE. In fact, in many cases these methods are the only things available for solving the problems. The book will cover the topic of computational electromagnetics in eddy-current nondestructive evaluation (NDE) by emphasizing three distinct topics: (a) fundamental mathematical principles of volume-integral equations as a subset of computational electromagnetics, (b) mathematical algorithms applied to signal-processing and inverse scattering problems, and (c) applications of these two topics to problems in which real and model data are used. This will make the book more than an academic exercise; we expect it to be valuable to users of eddy-current NDE technology in industries as varied as nuclear power, aerospace, materials characterization and biomedical imaging. We know of no other book on the market that covers this material in the manner in which we will present it, nor are there any books, to our knowledge, that apply this material to actual test situations that are of importance to the industries cited. It will be the first book to actually define the modern technology of eddy-current NDE, by showing how mathematics and the computer will solve problems more effectively than current analog practice.