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This paper introduces new technique for qualitative analysis of multi-transient electromagnetic (MTEM) earth impulse response over complex geological structures. Instantaneous phase and frequency attributes were used in place of the conventional common offset section for improved qualitative interpretation of MTEM data by obtaining more detailed information from the earth impulse response. The instantaneous attributes were used to describe the lateral variation in subsurface resistivity and the visible geological structure with respect to given offsets. Instantaneous phase attribute was obtained by converting the impulse response into a complex form using the Hilbert transform. Conversely, the polynomial phase difference (PPD) estimator was favored over the center finite difference (CFD) approximation method in calculating the instantaneous frequency attribute because it is computationally efficient and has the ability to give a smooth variation of the instantaneous frequency over a common offset section. The observed results from the instantaneous attributes were in good agreement with both the subsurface model used and the apparent resistivity section obtained from the MTEM earth impulse response. Hence, this study confirms the capability of both instantaneous phase and frequency attributes as highly effective tools for MTEM qualitative analysis. [ABSTRACT FROM AUTHOR]

In traditional ground penetrating radar (GPR) field data processing, e.g. horizontal stacking and migration, the wave propagating phase velocity is commonly used, while field magnitude decay is neglected. We derived the scalar wave equation of an electric vector field or magnetic vector field component and proved that the solution of this equation is the product of a decaying exponential function factor and a solution factor, which satisfies the pure wave equation. The waveform decomposition allows the evaluation of the absorption coefficient using the amplitudes of GPR waves. A meaningful method for absorption coefficient estimation in the time domain was introduced and tests with synthesized data demonstrated that this method is simple and effective. This method can simplify the process of absorption estimation and has a practical application value. Therefore, it is not only important for GPR data processing but may also yield important information on ground electrical properties. • A new absorption coefficient β is defined. • A simple method for β estimation is introduced. • Stack and migration processing will be efficiently implemented after β is obtained. [ABSTRACT FROM AUTHOR]