Techniques and Results of Magnetotelluric and Geomagnetic Deep Soundings

CONTENTS

1. Introduction, ...3
2. Detection and recording methods of Earth's electromagnetic field variations, ...6
  2.1. Torque balance magnetometers, ...6
  2.2. Induction coil magnetometers, ...9
  2.3. Proton and optical pumping magnetometers, ...10
  2.4. Flux gate magnetometers, ...10
  2.5. Recording methods of electromagnetic field variations and short review of typical variation stations, ...11
3. Statistical methods of Earth electromagnetic field variation treatment, ...12
  3.1. Statistical pattern of Earth's magnetic field, ...13
  3.2. Continuous and discrete Fourier transform, ...14
  3.3. Methods of magnetotelluric analyses, ...17
    3.3.1. Least square method, ...19
    3.3.2. Methods based on calculation of power spectra, ...21
  3.4. Simplifications used in analyses of magnetotelluric variations, ...34
4. Models, ...35
  4.1. Formulating of the problem of plane wave scattering on two- and one-dimensional models, ...36
  4.2. Linear relations between electromagnetic field components, ...39
  4.3. One-dimensional models, ...44
  4.4. Two-dimensional models, ...51
    4.4.1. Two-dimensional models as generalisation of an one-dimensional model, ...51
    4.4.2. Analytical solutions for two-dimensional models, ...56
    4.4.3. Finite difference method for numerical solutions of two-dimensional models, ...58
    4.4.4. Method of integral equations and their numerical solutions for a two-dimensional model, ...66
4.5. Some general regularities of models, ...72
    4.5.1. Damping of electromagnetic waves in a conductive medium, ...72
    4.5.2. Anisotropy and horizontal inhomogeneities, ...75
    4.5.3. Equivalency principle, ...76
5. Interpretation of magnetotelluric and geomagnetic soundings, ...78
  5.1. Interpretation purposes, ...78
  5.2. Model selection principles and comparison of experimental and model data, ...79
  5.3. Methods of fitting experimental data, ...80
6. Empirical curves of deep magnetotelluric soundings, ...81
  6.1. List of sounding curves, ...81
  6.2. Interpretation of experimental curves by simplified models and its limitation, ...104
  6.3. Magnetotelluric soundings in regions of simple conductivity distribution, ...106
7. Geomagnetic soundings, ...112
  7.1. Listing of measurement results of geomagnetic induction vectors, ...113
  7.2. Interpretation of geomagnetic vectors surface distribution, ...115
8. Conclusions and prospects of further research activities, ...120
References, ...123