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A new towed-transient electromagnetic system – tTEM, for fast and cost-effective high resolution 3D subsurface mapping

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We present a new and versatile towed- transient electromagnetic system (tTEM), capable of mapping the subsurface up to depth of 100 m. The system is not only suitable for ground-based application but also in aquatic (rivers, lakes etc.) environments. The tTEM system can map the subsurface with high resolution both vertically (shallow resolution is about 2-3 m) and horizontally (down to 10 x 10 m), depending on the resistivity structures. To achieve this goal, the system uses a one-turn 4 x 2 m2 transmitter loop mounted on a frame on sledges and towed by an all-terrain vehicle (ATV). The receiver coil has an effective area of20m2and placed in a 9 m offset configuration. The system operates at low and high transmitter moments (LM, HM) to achieve both shallow and deep information. The LM transmits 9.0 Amp with a turn-off time of 2.8 us and a first usable gate at 4 us (times from beginning of the ramp) while HM transmits 30 Amp. The repetition frequencies for the two moments are approx. 2000 Hz and 800 Hz. A full dataset is obtained every 0.8 sec corresponding to 3 -4 m spacing between soundings with a production speed of 15 – 25 km/h. Data are inverted using Aarhus Workbench following the well-established processing scheme for airborne transient electromagnetic data. In Denmark and other part of Europe, the tTEM system is being used for mapping geology, raw materials, aquifer vulnerability, shallow soil with respect to construction, nitrate-retention potential, and pathways contributing to flow and transport of contaminants. The other version of the system used on water is called FloaTEM. FloaTEM surveys were conducted in Denmark and several parts of United States including the Mississippi delta region for mapping and characterizing the alluvial aquifer system below the river beds. In the presentation, we will discuss the system design and demonstrate the imaging capability of the system with examples.

Original languageEnglish
Title of host publication1st Indian Near Surface Geophysics Conference and Exhibition
Number of pages6
PublisherEuropean Association of Geoscientists and Engineers, EAGE
Publication year2019
ISBN (Electronic)9789462823358
Publication statusPublished - 2019
Event1st Indian Near Surface Geophysics Conference and Exhibition, INSG 2019 - Virtual, Online
Duration: 28 Nov 201929 Nov 2019


Conference1st Indian Near Surface Geophysics Conference and Exhibition, INSG 2019
ByVirtual, Online
Series1st Indian Near Surface Geophysics Conference and Exhibition

Bibliographical note

Funding Information:
The study has been funded by Innovation Fund Denmark, project r Open (Open landscape nitrate retention mapping), Map Field (Field-scale mapping for targeted N-regulation and management) and the Inter reg VB North Sea Region project TOPSOIL. We are also grateful for the permission from Jens Demant Bernth from Orbicon A/S, Rikke Ellemann-Biltoft from Region Northern Jutland and Central Denmark Region to show the mapping examples. Finally, the Aarhus University center for water technologies, WATEC, has supported the developments.

Publisher Copyright:
© 2019 1st Indian Near Surface Geophysics Conference and Exhibition. All rights reserved.

    Research areas

  • 3D Imaging, Electromagnetics, Hydro Geophysics, Resistivity, TEM

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