Transient CFS response over a two-layer Earth

A Fourier series approach is used for computation of the time domain CFS response over a two-layer earth. The normalised vertical magnetic fields computed with the help of a digital linear filter are summed at each Fourier component composing the excitation pulse to obtain the CFS time domain response. Alternatively, the theoretical expressions for time domain sounding can be evaluated using numerical integration techniques, namely the Gauss-quadrature method and Simpson's rule. The aim of the present paper is to present a comparative study of these three techniques. An error analysis is also done and the results and performances of various computational approaches analysed. The sets of curves computed for two-layer earth models by these three techniques for varying loop radius, r 2 / r 1 ratio and a/h 1 ratio under the influence of a half sinusoidal primary excitation pulse are presented here.