Distortions of EM transients in coincident loops at short time‐delays

Transient electromagnetic measurements with short time‐delays of transients are used for solving different problems within the upper part of a geoelectric section. However, it is necessary to take into consideration distortions connected with self‐transients within the transmitter–receiver system. From the practical point of view, it is important to estimate the minimum time‐delay after which these distortions may be neglected. We present such an estimation which uses a simple approximation method for a single‐loop (or coincident‐loop) configuration. For common values of the loop size (10 m × 10 m to 40 m × 40 m) and of the resistivity of a homogeneous half‐space (1–100 Ωm), the minimum time‐delay beyond which we can use a standard interpretation is in the range of 2–10 µs. This is equivalent to a minimum depth of investigation in the range of 1–30 m.