Contents
1 Development and Prospect of Transient Electromagnetic Method 1
1.1 Overview on TEM Method 1
1.2 The Development Direction of TEM 4
1.3 Frontier Subject of TEM Pseudo-seismic Migration and Imaging 8
1.3.1 TEM Imaging Based on Equivalent Time-Frequency Conversion 8
1.3.2 TEM Imaging Technology Based on the Wave Field Conversion 10
1.3.3 Reverse Time Migration and Imaging Method 11
1.4 Research Progress of Pseudo-seismic Migration and Imaging in TEM 13
References 14
2 Theory and Technology of Full-Zone Wave Field Transformation 17
2.1 Theoretical Formula Construction 18
2.2 Ill-Posedness of Inverse Wave Field Transformation Analysis 19
2.3 Numerical Methods for Wave Field Transformation 20
2.4 Preconditioned Conjugate Gradient Regularization for Inverse Wave Field Transformation 26
2.5 Correlation Stacking Method for Extracting Pseudo Wave Field 31
2.6 Effectiveness Test of the Algorithm 33
References 37
3 Property of TEM Pseudo Wave Field 39
3.1 Two-Layer Model Analysis 39
3.1.1 Wave Field with Single Positive Peak 39
3.1.2 Wave Field with Single Negative Peak 44
3.2 Three-Layer Model Analysis 49
3.2.1 Q-Type Model with Double Positive Peaks 49
3.2.2 H-Type Model with Positive-Negative Peaks 52
3.2.3 K-Type Model with Negative-Positive Peaks 52
3.2.4 A-Type Model with Double Negative Peaks 57
3.3 Wave Field Characteristics of Time-Domain EM Responses with Noise 57
4 Synthetic Aperture Algorithms and Compression of Wavelet Width 75
4.1 Imaging Method Based on Synthetic Aperture 75
4.2 Compression of Wavelet Width 77
4.2.1 The Phenomenon of Waveform Dispersion 77
4.2.2 The Reason of Waveform Dispersion 78
4.2.3 Waveform Dispersion Compression Based on Deconvolution 79
4.2.4 Model Calculations 82
Reference 85
5 Surface Continuation and Imaging of TEM Based on Pseudo Wave Equations 87
5.1 Establishment of Kirchhoff Diffraction Integral 87
5.2 Migration by Kirchhoff Integration (Surface Continuation) 93
5.3 Boundary Element Method for Wave Field Continuation 95
5.3.1 Discretization of Kirchhoff Integration 95
5.3.2 Analysis on Elements 95
5.3.3 Total Matrix 97
5.3.4 Integration Over Elements 98
6 Velocity Analysis of TEM Pseudo Wave Field 105
6.1 Velocity Modelling Based on Equivalent Conductive Plate Method 105
6.1.1 Basic Theory of Equivalent Conductive Plate Method 106
6.1.2 Approximate Calculation of TEM Field at the Surface of a Horizontally Layered Earth 108
6.1.3 Optimized Extraction of Parameter m 110
6.2 Velocity Model for Single Observation Point 112
6.3 Continuous Velocity Analysis 114
6.3.1 Weighted Interpolation Based on Global Distance 114
6.3.2 Localized Linear Interpolation 115
7 Imaging of Theoretical Model and Field Examples 125
7.1 Model Calculations 125
7.1.1 Layered Model 125
7.1.2 Three-Dimensional Model 126
7.2 Examples with Field Data 131
7.2.1 Advanced Detection of Tunnel 131
7.2.2 Detection of Goaf of Coal Mine 135
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