The effect of ramp function turn-off on the TEM response of layered earth

Abstract

Formulae for the transient electromagnetic response of a layered half-space for ramp function current turn-offs are derived for coincident loop, vertical dipole and horizontal dipole receiver configurations. For the case of a uniform half-space, these take the form of an easily summed series. The errors involved in assuming the ramp function to be a step function are illustrated for four different earth models. An apparent resistivity algorithm for the coincident loop configuration is also presented.