Application of frequency-domain helicopter-borne electromagnetics for groundwater exploration in urban areas

Siemon, B.; Steuer, A.; Ullmann, A.; Vasterling, Margarete; Voß, W.

doi:10.1016/j.pce.2011.02.006

Cited by 36 publications

(23 citation statements)

References 38 publications

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“…at greater depths, this has to be taken into account during interpretation (Siemon et al . ). 3D effects occur in AEM data if the resistivity varies strongly in lateral direction (Sengpiel and Siemon ).…”

Section: Airborne Surveymentioning

confidence: 97%

Applying airborne electromagnetics in 3D stochastic geohydrological modelling for determining groundwater protection

Gunnink

Siemon

2014

Near Surface Geophysics

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Airborne electromagnetic (AEM) measurements provide information regarding the electrical properties of the subsurface for large spatial coverage in a limited time. In mapping and modelling for geological and geohydrological purposes, electrical properties (e.g. resistivity) need to be converted to relevant parameters, like lithology. Helicopter‐borne frequency‐domain EM measurements from an area in the Netherlands were combined with borehole data to create a 3D model of two contrasting lithologies (sand and clay) that served as proxy for assessing the vulnerability of the aquifer to surface contamination. By comparing the lithology found in boreholes with the resistivity derived from AEM at that location, a probabilistic relationship between these two variables was determined. This relationship was used to convert the AEM resistivity models into a 3D model of clay probability. Using geostatistical Monte Carlo simulations, the boreholes (hard data) and the probability of clay from the AEM resistivity models (soft data) were combined. AEM improved the 3D model substantially, compared to using only borehole data. An independent validation dataset verified the improvement of the 3D model using AEM data. Areas with a high probability of clay occurrence could be distinguished and a clay thickness map with uncertainty (standard deviation) was calculated. Using a simple groundwater model, the capability of the clay to protect the underlying aquifer from contamination was quantified. This resulted in the delineation of distinct areas that are well protected due to the large travel time for infiltrating water from the surface to the aquifer.

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Section: Airborne Surveymentioning

confidence: 97%

Applying airborne electromagnetics in 3D stochastic geohydrological modelling for determining groundwater protection

Gunnink

Siemon

2014

Near Surface Geophysics

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“…Tølbøll, 2007;Siemon et al, 2011). However, the noise effects of anthropogenic structures and soundings in the airborne electromagnetic data can hinder a proper geological interpretation, e.g.…”

Section: Discussionmentioning

confidence: 99%

“…erroneous data from anthropogenic noise (Siemon et al, 2011). 2) 1D AEM inversion models are always simplified realisations of the subsurface resistivity distribution, particularly if only models with few layers are used to explain the AEM data.…”

Section: Oligocenementioning

confidence: 99%

Towards an improved geological interpretation of airborne electromagnetic data: a case study from the Cuxhaven tunnel valley and its Neogene host sediments (northwest Germany)

Steinmetz

Winsemann

Brandes

et al. 2014

Netherlands Journal of Geosciences

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Airborne electromagnetics (AEM) is an effective technique for geophysical investigations of the shallow subsurface and has successfully been applied in various geological settings to analyse the depositional architecture of sedimentary systems for groundwater and environmental purposes.However, interpretation of AEM data is often restricted to 1D inversion results imaged on resistivity maps and vertical resistivity sections. The integration of geophysical data based on AEM surveys with geological data is often missing and this deficiency can lead to uncertainties in the interpretation process. The aim of this study is to provide an improved methodology for the interpretation of AEM data and the construction of more realistic 3D geological subsurface models. This is achieved by the development of an integrated workflow and 3D modelling approaches based on combining different geophysical and geological data sets (frequency-domain helicopter-borne electromagnetic data (HFEM), time-domain helicopter-borne electromagnetic data (HTEM), three 2D reflection seismic sections and 488 borehole logs). We used 1D inversion results gained from both HFEM and HTEM surveys and applied a 3D resistivity gridding procedure based on geostatistical analyses and interpolation techniques to create continuous 3D resistivity grids. Subsequently, geological interpretations have been performed by combining with, and validation against, borehole and reflection seismic data. To verify the modelling results and to identify uncertainties of AEM inversions and interpretation, we compared the apparent resistivity values of the constructed 3D geological subsurface models with those of AEM field measurements. Our methodology is applied to a test site near Cuxhaven, northwest Germany, where Neogene sediments are incised by a Pleistocene tunnel valley. The Neogene succession is subdivided by four unconformities and consists of fine-grained shelf to marginal marine deposits. At the end of the Miocene an incised valley was formed and filled with Pliocene delta deposits, probably indicating a palaeo-course of the River Weser or Elbe. The Middle Pleistocene (Elsterian) tunnel valley is up to 350 m deep, 0.8-2 km wide, and incised into the Neogene succession. The unconsolidated fill of the Late Miocene to Pliocene incised valley probably formed a preferred pathway for the Pleistocene meltwater flows, favouring the incision. Based on the 3D AEM resistivity model the tunnel-valley fills could be imaged in high detail. They consist of a complex sedimentary succession with alternating fine-and coarse-grained Elsterian meltwater deposits, overlain by glaciolacustrine (Lauenburg Clay Complex) and marine Holsteinian interglacial deposits.The applied approaches and results show a reliable methodology, especially for future investigations of similar geological settings. The 3D resistivity models clearly allow a distinction to be made between different lithologies and enables the detection of major bounding surfaces and architectural elements.

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“…The images related to the anomalous magnetic field and the first vertical derivative were generated and interpreted from the aeromagnetic data. Apparent conductivity images for coaxial dipole mode were created and analyzed from the aero-electromagnetic data, at 900 and 4500 Hz frequencies, since they characterize better vertical geologic structures, such as faults and fractures (Siemon et al, 2011). Satellite imaging is a powerful tool in structural analysis of large areas and thus extensively applied for water prospecting in fractured areas (Coriolanus, 2002;Leite, 2008;Ranganai & Ebinger, 2008).…”

Section: Airborne and Ground Geophysics Applied To Groundwater Prospementioning

confidence: 99%

“…The presence of water in these structures creates a good resistivity contrast compared to adjacent non-fractured rocks (Yadav & Singh, 2007), so the electromagnetic geophysical methods are widely applied to map brittle structures capable of storing water in the subsurface (Porsani et al, 2005;Feitosa et al, 2008). This method also provides information on water quality and aquifer conditions since the investigated parameter is electrical conductivity (Paterson & Bosschart, 1987;Siemon et al, 2009;Souza Filho et al, 2010;Siemon et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Airborne and Ground Geophysics Applied to Groundwater Prospection in Hard Rocks in Irauçuba, Ceará State, Brazil

Pinéo¹,

Branco²,

Cunha

et al. 2013

Rev. Bras. Geof.

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ABSTRACT. This work involved geophysical prospecting techniques, remote sensing and litho-structural recognition, applied to groundwater research in a region formed by hard rocks located in Irauçuba, Ceará State, Brazil. Geophysical magnetic and electromagnetic airborne data compiled from PROASNE project (Projetó Agua Subterrânea do Nordeste do Brasil ), Landsat ETM7 satellite images and electromagnetic land data, acquired in this research, were studied and allowed mapping lineaments related to geological structures, properly characterized by structural recognition on the field. The integrated analysis of geophysical and geological data, including hydrogeological information from deep wells, allowed understanding the pattern of fractures in the area, correlating the structures with the geological event responsible for their genesis and determining their hydrogeological potential. The results culminated in a structural-hydrogeological local model to be applied in areas with similar geological features. According to this model, geological brittle structures with approximate N-S direction are little penetrative and contribute to the recharge structures of WNW-ESE direction, which are the most promising for groundwater exploitation through deep wells.Keywords: groundwater in hard rocks, geophysics prospection, remote sensing. RESUMO.Este trabalho envolveu técnicas geofísicas de prospecção, sensoriamento remoto e reconhecimento lito-estrutural, aplicadosà pesquisa deágua subterrânea em uma região formada por rochas cristalinas, localizada no município de Irauçuba, Estado do Ceará, Brasil. Dados geofísicos magnéticos e eletromagnéticos aerotransportados compilados do projeto PROASNE (ProjetoÁgua Subterrânea do Nordeste do Brasil), imagens do satélite LandSat ETM7 e dados eletromagnéticos terrestres, adquiridos nesta pesquisa, foram trabalhados de forma integrada e permitiram cartografar lineamentos referentes a estruturas geológicas diversas, devidamente caracterizados através de reconhecimento estrutural em atividade de campo. A análise integrada dos dados geofísicos e geológicos, incluindo informações hidrogeológicas de poços profundos, possibilitou compreender o padrão de fraturas daárea, correlacionar as estruturas com o evento geológico responsável por sua gênese e determinar o potencial hidrogeológico destas estruturas. Os resultados obtidos culminaram em um modelo estrutural-hidrogeológico local, de aplicação eḿ areas com características geológicas similares. De acordo com o referido modelo, estruturas geológicas rúpteis de direção aproximada N-S são pouco penetrativas e tem como função principal contribuir com a recarga das estruturas de direção WNW-ESE, que são mais promissoras a explotação deágua subterrânea por meio de poço tubular profundo.Palavras-chave: aquifero fissural, geofísica de prospecção, sensoriamento remoto.

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Application of frequency-domain helicopter-borne electromagnetics for groundwater exploration in urban areas

Cited by 36 publications

References 38 publications

Applying airborne electromagnetics in 3D stochastic geohydrological modelling for determining groundwater protection

Applying airborne electromagnetics in 3D stochastic geohydrological modelling for determining groundwater protection

Towards an improved geological interpretation of airborne electromagnetic data: a case study from the Cuxhaven tunnel valley and its Neogene host sediments (northwest Germany)

Airborne and Ground Geophysics Applied to Groundwater Prospection in Hard Rocks in Irauçuba, Ceará State, Brazil

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