KEGS Presents: Airborne Inductively Induced Polarization effects in and their removal from VTEM™ data
Airborne inductively induced polarization (AIIP) effects, in the form of numerous negative transients, have been observed in the VTEM™ helicopter time-domain EM 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:
1. Electromagnetic induction related to ground conductivity and
2. 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 µs to 400 µs. Moreover, the earliest few time channels, from 18 µs to 48 µs, 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. AIIP mapping is applied to Mirny VTEM™ data, to extract chargeability and more accurate resistivity. In order to facilitate TDEM data processing software which do not take into account of AIIP, the AIIP effects assumed to be related to permafrost are removed by two ways.
Presented by Karl Kwan, Geotech LTD, at the KEGS (Canadian Exploration Geophysical Society) meeting on May 10, 2016.