A comparison of helicopter-borne electromagnetics in frequency- and time-domain at the Cuxhaven valley in Northern Germany

Steuer, A.; Siemon, B.; Auken, Esben

doi:10.1016/j.jappgeo.2007.07.001

Cited by 110 publications

(76 citation statements)

References 29 publications

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“…However, particular care must be taken to distinguish between fluid resistivity and lithology (Günther and Müller-Petke, 2012). Frequencydomain and time-domain airborne applications are available, and their worth has been proven during the last 10 yr Steuer et al, 2007). The collected data generally show a good data quality.…”

Section: Airborne Electromagnetic Datamentioning

confidence: 99%

Compiling geophysical and geological information into a 3-D model of the glacially-affected island of Föhr

Burschil

Scheer

Kirsch

et al. 2012

Hydrol. Earth Syst. Sci.

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Abstract. Within the scope of climatic change and associated sea level rise, coastal aquifers are endangered and are becoming more a focus of research to ensure the future water supply in coastal areas. For groundwater modelling a good understanding of the geological/hydrogeological situation and the aquifer behavior is necessary. In preparation of groundwater modelling and assessment of climate change impacts on coastal water resources, we setup a geological/hydrogeological model for the North Sea Island of Föhr.Data from different geophysical methods applied from the air, the surface and in boreholes contribute to the 3-D model, e.g. airborne electromagnetics (SkyTEM) for spatial mapping the resistivity of the entire island, seismic reflections for detailed cross-sections in the groundwater catchment area, and geophysical borehole logging for calibration of these measurements. An iterative and integrated evaluation of the results from the different geophysical methods contributes to reliable data as input for the 3-D model covering the whole island and not just the well fields.The complex subsurface structure of the island is revealed. The local waterworks use a freshwater body embedded in saline groundwater. Several glaciations reordered the youngest Tertiary and Quaternary sediments by glaciotectonic thrust faulting, as well as incision and refill of glacial valleys. Both subsurface structures have a strong impact on the distribution of freshwater-bearing aquifers. A digital geological 3-D model reproduces the hydrogeological structure of the island as a base for a groundwater model. In the course of the data interpretation, we deliver a basis for rock identification.We demonstrate that geophysical investigation provide petrophysical parameters and improve the understanding of the subsurface and the groundwater system. The main benefit of our work is that the successful combination of electromagnetic, seismic and borehole data reveals the complex geology of a glacially-affected island. A sound understanding of the subsurface structure and the compilation of a 3-D model is imperative and the basis for a groundwater flow model to predict climate change effects on future water resources.

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Section: Airborne Electromagnetic Datamentioning

confidence: 99%

Compiling geophysical and geological information into a 3-D model of the glacially-affected island of Föhr

Burschil

Scheer

Kirsch

et al. 2012

Hydrol. Earth Syst. Sci.

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“…The study area was covered by two airborne EM surveys using helicopter-borne frequency domain (HEM) and time domain (SkyTEM) systems often used in groundwater studies (Siemon et al, 2009b;Steuer et al, 2009). In a small part, the two surveys overlapped (see Fig.…”

Section: Airborne Emmentioning

confidence: 99%

Combining ground-based and airborne EM through Artificial Neural Networks for modelling glacial till under saline groundwater conditions

Gunnink

Bosch

Siemon

et al. 2012

Hydrol. Earth Syst. Sci.

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Abstract. Airborne electromagnetic (AEM) methods supply data over large areas in a cost-effective way. We used Artificial Neural Networks (ANN) to classify the geophysical signal into a meaningful geological parameter. By using examples of known relations between ground-based geophysical data (in this case electrical conductivity, EC, from electrical cone penetration tests) and geological parameters (presence of glacial till), we extracted learning rules that could be applied to map the presence of a glacial till using the EC profiles from the airborne EM data. The saline groundwater in the area was obscuring the EC signal from the till but by using ANN we were able to extract subtle and often non-linear, relations in EC that were representative of the presence of the till. The ANN results were interpreted as the probability of having till and showed a good agreement with drilling data. The glacial till is acting as a layer that inhibits groundwater flow, due to its high clay-content, and is therefore an important layer in hydrogeological modelling and for predicting the effects of climate change on groundwater quantity and quality.

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“…These systems are generally more expensive to operate than fixed-wing EM systems, but offer better spatial resolution. Time-domain methods offer advantages over frequency-domain methods, such as greater depth of investigation and detail, as well as more accurate mapping of freshwater/saltwater boundaries (Steuer et al 2009). …”

Section: Introductionmentioning

confidence: 99%

Three-dimensional resistivity modeling of GREATEM survey data from Ontake Volcano, northwest Japan

Allah

Mogi

2016

Earth Planet Sp

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Ontake Volcano is located in central Japan, 200 km northwest of Tokyo and erupted on September 27, 2014. To study the structure of Ontake Volcano and discuss the process of its phreatic eruption, which can help in future eruptions mitigation, airborne electromagnetic (AEM) surveys using the grounded electrical-source airborne transient electromagnetic (GREATEM) system were conducted over Ontake Volcano. Field measurements and data analysis were done by OYO Company under the Sabo project managed by the Ministry of Land, Infrastructure, Transport and Tourism. Processed data and 1D resistivity models were provided by this project. We performed numerical forward modeling to generate a three-dimensional (3D) resistivity structure model that fits the GREATEM data where a composite of 1D resistivity models was used as the starting model. A 3D electromagnetic forward-modeling scheme based on a staggered-grid finite-difference method was modified and used to calculate the response of the 3D resistivity model along each survey line. We verified the model by examining the fit of magnetic-transient responses between the field data and 3D forward-model computed data. The preferred 3D resistivity models show that a moderately resistive structure (30-200 Ω m) is characteristic of most of the volcano, and were able to delineate a hydrothermal zone within the volcanic edifice. This hydrothermal zone may be caused by a previous large sector collapse.

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A comparison of helicopter-borne electromagnetics in frequency- and time-domain at the Cuxhaven valley in Northern Germany

Cited by 110 publications

References 29 publications

Compiling geophysical and geological information into a 3-D model of the glacially-affected island of Föhr

Compiling geophysical and geological information into a 3-D model of the glacially-affected island of Föhr

Combining ground-based and airborne EM through Artificial Neural Networks for modelling glacial till under saline groundwater conditions

Three-dimensional resistivity modeling of GREATEM survey data from Ontake Volcano, northwest Japan

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