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Mapping geological structures in bedrock via large‐scale direct current resistivity and time‐domain induced polarization tomography
Author(s) -
Rossi Matteo,
Olsson PerIvar,
Johanson Sara,
Fiandaca Gianluca,
Preis Bergdahl Daniel,
Dahlin Torleif
Publication year - 2017
Publication title -
near surface geophysics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.639
H-Index - 39
eISSN - 1873-0604
pISSN - 1569-4445
DOI - 10.3997/1873-0604.2017058
Subject(s) - geology , bedrock , electrical resistivity tomography , subsoil , induced polarization , direct current , electrical resistivity and conductivity , hydrogeology , economic geology , regional geology , environmental geology , gemology , geophysics , tectonics , polarization (electrochemistry) , palaeogeography , borehole , engineering geology , overburden , time domain , geomorphology , seismology , soil science , geotechnical engineering , volcanism , soil water , voltage , chemistry , metamorphic petrology , quantum mechanics , telmatology , physics , electrical engineering , computer science , computer vision , engineering
An investigation of geological conditions is always a key point for planning infrastructure constructions. Bedrock surface and rock quality must be estimated carefully in the designing process of infrastructures. A large direct‐current resistivity and time‐domain induced‐polarization survey has been performed in Dalby, Lund Municipality, southern Sweden, with the aim of mapping lithological variations in bedrock. The geology at the site is characterised by Precambrian granitic gneisses and amphibolites, which are intensely deformed, fractured, and partly weathered. In addition, there are northwest‐trending Permian dolerite dykes that are less deformed. Four 2D direct‐current resistivity and time‐domain induced‐polarization profiles of about 1‐km length have been carefully pre‐processed to retrieve time‐domain induced polarization responses and inverted to obtain the direct‐current resistivity distribution of the subsoil and the phase of the complex conductivity using a constant‐phase angle model. The joint interpretation of electrical resistivity and induced‐polarization models leads to a better understanding of complex three‐dimensional subsoil geometries. The results have been validated by lithological descriptions from several drillings. In addition, direct‐current resistivity and time‐domain induced‐polarization logging has been carried out in two different boreholes, showing a good match with the results of the surface direct‐current resistivity and time‐domain induced‐polarization profiles. The direct‐current resistivity and time‐domain induced‐polarization methodology proved to be a suitable technique for extensively mapping weathered zones with poor geotechnical characteristics and tectonic structures, which can lead to severe problems for infrastructure construction and/or constitute risk zones for aquifer contamination.