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Induced Current System During the On-time of an AEM SystemNormal access

Authors: A. Smiarowski, G. Hodges and T. Chen
Event name: First European Airborne Electromagnetics Conference
Session: Hardware and Software Innovations
Publication date: 06 September 2015
DOI: 10.3997/2214-4609.201413872
Organisations: EAGE
Language: English
Info: Extended abstract, PDF ( 1.2Mb )
Price: € 20

Conductivity depth transforms are a useful tool for quickly creating a subsurface image from airborne electromagnetic data. Time-domain EM (TEM) transforms have utilized the response from a step-off waveform and a thin sheet or homogenous halfspace model to determine exploration depth. The induced current system from a step-off waveform has been studied in the literature. However, the current system from other waveforms, and in particular the current system during the on-time, has not been addressed. Here, we calculate the induced current for a halfsine waveform during the off-time and the on-time. We show that the on-time current density is concentrated near surface compared to the off-time. Using field data, we then compute the halfspace apparent resistivity for an on-time channel and the first off-time channel as well as five frequencies from a frequency domain survey; the on-time apparent resistivity correlates well with the high-frequency apparent resistivity while the first off-time channel correlates with a mid-frequency apparent resistivity.

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