Abstract
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.
Highlights
Uncertainty in subterraneous conditions can pose a risk to land and infrastructure.Traditional ground investigation methods that were once undertaken by foot are costly and time-consuming
One of the first known fixed-wing airborne electromagnetic (AEM) systems were successfully tested in Canada during the summer of 1948
We investigate the current state of AEM surveys in Norway for geological and geotechnical investigations
Summary
Uncertainty in subterraneous conditions can pose a risk to land and infrastructure.Traditional ground investigation methods that were once undertaken by foot are costly and time-consuming. A bedrock model training on over 850 geotechnical soundings only adds to the topographic ‘resolution’, in that high and low features become more exaggerated when compared to the model from five boreholes This shows that the effect of the additional boreholes serves to improve the areas where the 5 and 25 borehole models lack information, in regions of high or low bedrock elevation where they lack training data that would justify such extremes. Even with these extremes, a five borehole bedrock model prediction produces a representative early-stage view of subsurface conditions.
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