The characteristic periods of the induction arrows for a conductive-resistive vertical interface—a numerical model study

Abstract

The spatial dependence of the characteristic periods ( T c) of the induction arrows along a profile over a conductive plate-resistive host is investigated for two dimensional numerical models of a conductive plate of (i) semi-infinite and (ii) finite widths in uniform and layered resistive hosts. Induction arrows are computed for a large period range (2–25 600 s) at selected distances on either side of the conductive-resistive interface, and empirical curves for the characteristic period (period at which the quadrature induction arrow reverses sign) as a function of distance from the interface are presented. The characteristic period is seen to have a minimum value at the interface and then to increase with distance from the interface both over the conductive plate and the resistive host. The characteristic period at a given point on either side of the interface is also seen to increase with increasing depth of the conductive substratum. For the case of a finite width plate, a minimum in T c is observed at both plate boundaries. The characteristic periods at the interface, and at points on either side of the interface, are found generally to depend on the conductivities of the plate and host, the depth of burial and dimensions of the plate, and the depth of the conductive substratum. The results show that the characteristic periods at sites along a profile over a 2-D conductive body could, in principle, be used to delineate the location of the conductive-resistive interface, and provide information on the dimensions, depth of burial, and the conductivity of the conductive body in a host earth if the conductivity of the host and substratum were known.