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Electric and Electromagnetic Investigation of a Karst SystemNormal access

Authors: M.P. Miensopust, J. Igel, T. Günther, R. Dlugosch and S. Hupfer
Event name: Near Surface Geoscience 2015 - 21st European Meeting of Environmental and Engineering Geophysics
Session: Integration of Geophysics II
Publication date: 06 September 2015
DOI: 10.3997/2214-4609.201413704
Organisations: EAGE
Language: English
Info: Extended abstract, PDF ( 3.67Mb )
Price: € 20

Summary:
The limestone of the western flank of the Innerste Mulde in Lower Saxony, Germany, host a 27 km long karst water system which is surface-mapped by sinkhole and collapse structures. The karst water emerges at springs – one of them is a spring called Kirschensoog near the village of Altwallmoden which only temporarily yields water. From early March to mid March 2015 the water level fell visibly. During that time electric and electromagnetic methods were applied in the field and soil and rock samples were taken for laboratory studies. Field measurements comprise electrical resistivity tomography (ERT), ground penetrating radar (GPR) and 2D nuclear magnetic resonance (NMR) surveys. The laboratory measurements (e.g. NMR and spectral induced polarisation measurements, petrophysical studies, dielectric spectroscopy) are applied to support the interpretation of the field data. The preliminary results show that the covering, clay-rich soil has a strong attenuation restricting the investigation depth of GPR. The ERT models indicate a 3D subsurface structure and – as well as GPR – suggest dipping structures possibly related to the bedding of the limestone or fissures/ fractures. The rather low resistivity of the limestone might be an indication of disruption and presence of fluids.


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