The time-domain electromagnetic response of wedge-like structures

Abstract

Wedges are structures that vary in thickness from top to bottom over length. Despite their application to modelling the regolith, groundwater and bathymetric problems, wedges have not been studied in any great detail. We simulated the response of wedge-like structures using Tempest and HoisTEM-like AEM systems and a fixed-loop SIROTEM ground system. We found that it was very difficult to distinguish between the responses of wedges with different dips until smoke rings had penetrated the conductive outcropping wedge. This means that thinner wedges are easier to see than thicker wedges. It also implies that a vertical block might be a useful approximation to thicker wedges. Differentiation of wedge responses was best achieved using the vertical component of a fixed loop positioned off the wedge. Inline components of central-loop prospecting systems were useful as ``bump detectors'.