Improved near-surface resolution in geotechnical applications using very early AEM time gates

Skurdal, Guro Huun; Pfaffhuber, Andreas Aspmo; Davis, Aaron; Bazin, Sara

doi:10.1080/08123985.2019.1691441

Cited by 3 publications

(3 citation statements)

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“…A high altitude (>300 m above ground) test flying was carried out at the beginning and at the end of each flight to measure the primary field response, that is, the effects of the instrument including the helicopter on the receiver coil. The high‐altitude primary field response was used to decouple the system response from the early time gates (∼1 μs) of low moment data (Auken et al., 2020; Skrudal et al., 2020). Thus, the low and the high moment measurements added to the system response decoupling from early gates facilitate usable TEM data starting from 4 to ∼10 μs that results into obtaining high‐resolution subsurface characteristics from very shallow to more than 250 m depth.…”

Section: Methodsmentioning

confidence: 99%

Airborne Electromagnetic Signatures of an Ancient River in the Water‐Stressed Ganga Plain, Prayagraj, India: A Potential Groundwater Repository

Chandra

Tiwari

Vidyasagar

et al. 2021

Geophysical Research Letters

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In the past few decades, rapid population growth, increasing agricultural practices and industrialization have transformed the water ecosystem around the world (Aeschbach-Hertig & Gleeson, 2012). More than 40% world's population currently lives in water stressed river basins. Excessive groundwater exploitation in comparison to the recharge causes depletion and deterioration of groundwater resources, resulting in drying up of the lakes and rivers, etc. Due to heavy dependence of irrigation on groundwater resources many leading food grains producing countries like USA, China, India, and Australia are reaching their water resource limits. India is one of the worst affected countries facing imminent water crisis (NITI, 2018). The Ganga basin known to hold voluminous amount of groundwater in multi-layered aquifer system caters to the groundwater needs of a large population of India (Das & Tamminga, 2012;Bank, 2014). However, it is under heavy stress with a large-scale depletion and quality deterioration of the groundwater leading to environmental, economic and health issues (Asoka et al., 2017;Fendorf & Benner, 2016;Tiwari et al., 2009). The problem is most alarming in the "Doab (interfluve)" region bounded by the Ganga and Yamuna rivers. The poor water quality pervades not only the Ganga and Yamuna Rivers but also seems to be entering the associated aquifers (Misra & Mishra, 2007;Prakash et al., 2020).Managed aquifer recharge (MAR) programs are the most effective and environmental-friendly solution to achieve sustainable water security (Dillon et al., 2010). An effective MAR program necessitates high-resolution

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Section: Methodsmentioning

confidence: 99%

Airborne Electromagnetic Signatures of an Ancient River in the Water‐Stressed Ganga Plain, Prayagraj, India: A Potential Groundwater Repository

Chandra

Tiwari

Vidyasagar

et al. 2021

Geophysical Research Letters

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“…However, AEM has several limitations on its utility for ground investigations. First, the resolution is rather low and may not always be sufficient for all applications, though efforts are ongoing to extract early-time/high-frequency signal to improve near-surface resolution [66]. Second, accounting for 3D effects is computationally intensive, meaning that the most commonly used inversion schemes result in models with a high degree of lateral smoothing.…”

Section: Generalizations: Advantages and Limitations Of Aem For Ground Investigationsmentioning

confidence: 99%

AEM in Norway: A Review of the Coverage, Applications and the State of Technology

Harrison¹,

Baranwal

Pfaffhuber³

et al. 2021

Remote Sensing

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From the first use of airborne electromagnetic (AEM) systems for remote sensing in the 1950s, AEM data acquisition, processing and inversion technology have rapidly developed. Once used extensively for mineral exploration in its early days, the technology is increasingly being applied in other industries alongside ground-based investigation techniques. This paper reviews the application of onshore AEM in Norway over the past decades. Norway’s rugged terrain and complex post-glacial sedimentary geology have contributed to the later adoption of AEM for widespread mapping compared to neighbouring Nordic countries. We illustrate AEM’s utility by using two detailed case studies, including time-domain and frequency domain AEM. In both cases, we combine AEM with other geophysical, geological and geotechnical drillings to enhance interpretation, including machine learning methods. The end results included bedrock surfaces predicted with an accuracy of 25% of depth, identification of hazardous quick clay deposits, and sedimentary basin mapping. These case studies illustrate that although today’s AEM systems do not have the resolution required for late-phase, detailed engineering design, AEM is a valuable tool for early-phase site investigations. Intrusive, ground-based methods are slower and more expensive, but when they are used to complement the weaknesses of AEM data, site investigations can become more efficient. With new developments of drone-borne (UAV) systems and increasing investment in AEM surveys, we see the potential for continued global adoption of this technology.

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“…Near-surface resolution can be further improved when methods are used to incorporate time gates that are either closer to the transmitter current shut-off or are in the on-time of the transmitting waveform. Guro Skurdal, Andi Pfaffhuber, Aaron Davis, and Sara Bezin show that early time gates can improve near-surface resolution in AEM data (Skurdal et al 2019); and Esben Auken, Nikolaj Fogel, Kristoffer Andersen, Niklas Nyboe, and Anders Christiansen demonstrate improved resolution using on-time data .…”

Section: Introduction Aaron Davismentioning

confidence: 99%

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2020

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Improved near-surface resolution in geotechnical applications using very early AEM time gates

Cited by 3 publications

References 10 publications

Airborne Electromagnetic Signatures of an Ancient River in the Water‐Stressed Ganga Plain, Prayagraj, India: A Potential Groundwater Repository

Airborne Electromagnetic Signatures of an Ancient River in the Water‐Stressed Ganga Plain, Prayagraj, India: A Potential Groundwater Repository

AEM in Norway: A Review of the Coverage, Applications and the State of Technology

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