When modelling EM data, it is not necessary to specify all parts of the transmitter current waveform precisely. Accurate responses can be obtained if the latter part of the waveform is specified precisely; the early part can be expressed approximately, provided the area under the waveform curve is precise.

The SPM decay can be approximated as a decay proportional to time to the inverse power. We use this approximation with least-squares fitting to distinguish SPM effects from the response of a conductor. Application shows that it aids significantly in conductive target identification.

EM34, VLF and DC-resistivity methods have been effectively used to investigate the environmental impact of a coal waste pile at the Alborz Sharghi coal washing plant, north-east Iran. Two-dimensional resistivity sections and quasi-three-dimensional models obtained by the inversion of EM34 conductivity data together with the results of VLF and DC-resistivity methods have identified conductive leachate plumes downstream of the waste pile and decreasing resistivity at deeper levels of the earth due to the migration of contaminated plumes.

In this paper, the split perfectly matched absorbing layer is extended to fluid-saturated porous anisotropic media based on Biot’s equations and the staggered-grid finite-difference method. The results from homogeneous and heterogeneous models show that the algorithm is stable and efficient for modelling in these media.

The confined compressive strength–seismic velocity relationship is modelled by combining two effective-medium models for the confined compressive strength versus porosity and seismic velocity versus porosity. The model is verified through its application to actual seismic P- and S-wave velocities and confined compressive strength data of sedimentary rocks.

A new edge detection filter to delineate the edges of the source automatically, called the improved local phase (ILP) filter, is presented. The ILP filter is formed by the first- and second-order horizontal derivatives, so it is computationally stable.

This paper compares three methods which remove unwanted edge contours from gravity datasets. The first method removes edges which are not present in the data after its upward continuation to a given height, the second method removes edges whose amplitude is below a given threshold, while the final method removes the shortest edge contours.

This paper describes the use of magnetic susceptibility measurements on soil samples. In the deeply weathered lateritic context of the study area, soil magnetic susceptibility reveals similarities with magnetic/geochemical survey results, suggesting this rapid and easy to use technique can be an effective tool for exploration and geological programs.

A novel approach is proposed for estimating uranium grades from gamma-ray probes, which is demonstrated for the Angela deposit. Gamma-ray transport modelling of the unique probe response (including energy threshold) is allied with the response from model pits to correct for casing, water, borehole diameter, dead-time and the Z-effect.