Abstract

Coincident-loop TEM sounding data are often presented by plotting the half-space apparent conductivity as a function of delay time. A new algorithm generates an improved presentation that plots the apparent conductivity as a function of depth. The resulting data may be further processed to sharpen or “spike” the smoothly varying apparent-conductivity/depth curves in an attempt to better represent the rapid changes in conductivity that often exist in the earth. The algorithm described involves an approximation, but is simple, easy to use, and computationally efficient.

A layered conductivity structure is assumed, so the algorithm is best for areas where the geology is approximately horizontal. However, the algorithm can also be used to identify anomalous features that are not infinite horizontal layers. The spiked conductivity models derived from synthetic data are consistent with the original layered-earth models and show a greater resolution than the apparent-conductivity/depth curves, and sometimes amplify noise in the data.

When data are collected along a profile line, the conductivity/depth information can be converted to a color image. For profile data collected over the Elura orebody, the image of the spiked conductivity section shows an anomalous feature at the orebody, and the color contrast is more marked than it is on the apparent-conductivity/depth image.

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