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Open AccessArticle

Detection of Cover Collapse Doline and Other Epikarst Features by Multiple Geophysical Techniques, Case Study of Tarimba Cave, Brazil

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Environmental Engineering and Earth Science Department, 445 Bracket Hall, Clemson University, Clemson, SC 29634, USA
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Department of Geography, University of Brasilia, Brasilia 70910-900, Brazil
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Institute of Geosciences, University of Brasilia, Brasilia 70910-900, Brazil
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Institute of Astronomy, Geophysics and Atmospheric Sciences, São Paulo University (USP), São Paulo 05508-090, Brazil
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School of Natural and Built Environment, College of Science and Engineering, University of Derby, Derby DE22 AW, UK
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Facultad de Ingeniería, Universidad Nacional Autónoma de México UNAM, Mexico City 04510, Mexico
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Geology Department, Liège University, 4032 Liège, Belgium
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Department of Civil and Environmental Engineering, Nagaoka University of Technology, 1603-1, Kami-Tomioka, Nagaoka 940-2188, Japan
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Author to whom correspondence should be addressed.
Water 2020, 12(10), 2835; https://doi.org/10.3390/w12102835
Received: 18 August 2020 / Revised: 26 September 2020 / Accepted: 28 September 2020 / Published: 12 October 2020
(This article belongs to the Section Hydrology and Hydrogeology)
Reliable characterization of the karst system is essential for risk assessment where many associated hazards (e.g., cover-collapse dolines and groundwater pollution) can affect natural and built environments, threatening public safety. The use of multiple geophysical approaches may offer an improved way to investigate such cover-collapse sinkholes and aid in geohazard risk assessments. In this paper, covered karst, which has two types of shallow caves (vadose and fluvial) located in Tarimba (Goias, Brazil), was investigated using various geophysical methods to evaluate their efficiency in the delineation of the geometry of sediments filled sinkhole. The methods used for the investigation were Electrical Resistivity Tomography (ERT), Seismic Refraction Survey (SRS), Seismic Refraction Tomography (SRT) and the Very Low Frequency Electromagnetic (VLF-EM) method. The study developed several (2D) sections of the measured physical properties, including P-wave velocity and electrical resistivity, as well as the induced current (because of local bodies). For the analysis and processing of the data obtained from these methods, the following approaches were adopted: ERT inversion using a least-square scheme, Karous-Hjelt filter for VLF-EM data and time-distance curves and Vp cross-sections for the SRS. The refraction data analysis showed three-layered stratigraphy topsoil, claystone and carbonate bedrock, respectively. The findings obtained from ERT (three-layered stratigraphy and sediment-filled doline), as well as VLF-EM (fractured or filled caves as a positive anomaly), were found to be consistent with the actual field conditions. However, the SRS and SRT methods did not show the collapsed material and reached the limited the depth because of shorter profile lengths. The study provides a reasonable basis for the development of an integrated geophysical approach for site characterization of karst systems, particularly the perched tank and collapse doline. View Full-Text
Keywords: ERT; SRS; three-layered stratigraphy; VLF-EM ERT; SRS; three-layered stratigraphy; VLF-EM
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Hussain, Y.; Uagoda, R.; Borges, W.; Prado, R.; Hamza, O.; Cárdenas-Soto, M.; Havenith, H.-B.; Dou, J. Detection of Cover Collapse Doline and Other Epikarst Features by Multiple Geophysical Techniques, Case Study of Tarimba Cave, Brazil. Water 2020, 12, 2835.

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