Airborne Inductively Induced Polarization effects in and their removal from the VTEM data from Mirny, Russia

Abstract

Summary Airborne inductively induced polarization (AIIP TM ) effects, in the form of numerous negative transients, have been observed in the VTEM helicopter time-domain EM (TDEM) data from Mirny, Russia. The survey area is located in the continuous permafrost zone. Inductively induced polarization (IIP) effects in ground TDEM data had earlier been reported from the same region. VTEM data reflect mainly two physical phenomena in the earth: i) electromagnetic induction and ii) airborne inductively induced polarization (AIIP) related to the relaxation of polarized charges in the ground. Typical AIIP effects in the VTEM data from Mirny corrupt only the early to mid-time channels, from 55 s to 400 s. Moreover, the earliest few time channels, from 18 s to 48 s, are not affected by AIIP, because the IP effect takes a finite time to build up. Cole-Cole analysis of the AIIP affected VTEM data showed that the frequency factor and the time constant are close to 0.8 and 0.0001s, respectively. Since the earliest time channel data are not affected by AIIP, the resistivity of the shallow ground can still be precisely determined. As a result, the purely inductive VTEM decay can be accurately modelled and used to remove the AIIP effect from later time-channels.