Koefoed has given practical procedures of obtaining the layer parameters directly from the apparent resistivity sounding measurements by using the raised kernel function H(λ) as the intermediate step. However, it is felt that the first step of his method—namely the derivation of the H curve from the apparent resistivity curve—is relatively lengthy. In this paper a method is proposed of determining the resistivity transform T(λ), a function directly related to H(λ), from the resistivity field curve. It is shown that the apparent resistivity and the resistivity transform functions are linearily related to each other such that the principle of linear electric filter theory could be applied to obtain the latter from the former. Separate sets of filter coefficients have been worked out for the Schlumberger and the Wenner form of field procedures. The practical process of deriving the T curve simply amounts to running a weighted average of the sampled apparent resistivity field data with the pre‐determined coefficients. The whole process could be graphically performed within an quarter of an hour with an accuracy of about 2%.

In this paper a fast method is developed for computing apparent resistivity curves for known layer configurations. The method is based on the application of a linear filter to determine the apparent resistivity curve from, the kernel function.

The computation method described in this paper is based on the existence of a linear relationship between the mutual coupling ratio and the kernel function in the integral expression for it. Accordingly, the mutual coupling ratio can be determined by first computing sample values of the kernel function and then subjecting these to a digital linear filter. In the present paper the appropriate sampling distance is determined and the values of the digital filter coefficients are computed, both for electromagnetic sounding with horizontal coils and for electromagnetic sounding with perpendicular coils.

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Malay Basin, a northward-trending pull-apart extensional rift basin, formed during the late Eocene-early Oligocene and then underwent thermal subsidence and sedimentation during the early Miocene. Reorientation of regional stress fields during the mid-Miocene caused structural inversion resulting in east-west anticlines and half grabens.