2D and 3D ERT imaging for identifying karst morphologies in the archaeological sites of Gran Dolina and Galería Complex (Sierra de Atapuerca, Burgos, Spain)

Bermejo, Lucía; Martínez, Ana Isabel Ortega; Guérin, Roger; Benito‐Calvo, Alfonso; Pérez‐González, Alfredo; Parés, Josep M.; Aracil, E.; Castro, José Marı́a Bermúdez de; Carbonell, Eudald

doi:10.1016/j.quaint.2015.12.031

Cited by 25 publications

(13 citation statements)

References 41 publications

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“…Such features were imaged by ERT, for example at X = 58 to 70 m on ERT1, as resistive lenses, and at X = 46 m on ERT1 and X = 58 m on ERT2, as conductive elements, and were also found by trench excavations. Highly heterogeneous structures (E15 in Figure 2b, E27 in Figure 2c) caused ERT to fail to resolve the contact between the urban fill and limestone, even within the interpretable DOI (as shown by Bermejo et al, 2017). Nevertheless, fixing EC 2 (the conductivity of the limestone) as 400 Ω m improved the consistency of the geophysical models obtained from the ERT and ES interpretations.…”

Section: Discussionmentioning

confidence: 96%

Geometrical characterization of urban fill by integrating the multi‐receiver electromagnetic induction method and electrical resistivity tomography: A case study in Poitiers, France

Fraga

Schamper

Noël

et al. 2019

European J Soil Science

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A geophysical survey including electromagnetic induction (EMI) and electrical resistivity tomography (ERT) methods was applied and assessed with a 40‐trench sampling grid to delineate the geometry of an urban fill layer. Classical investigation techniques, such as excavation, offer localized information and suffer from time and budget constraints for environmental assessments. Near‐surface geophysics can provide the required spatial sampling to evaluate the coverage of anthropogenic soils in a time‐effective and quasi‐continuous manner. Fast‐acquisition and high‐spatial‐coverage EMI mapping and high‐vertical‐resolution ERT were implemented to delineate a suspicious urban fill on a 5‐ha site in a suburban region, which will host the buildings of a commercial complex. The ERT data and 40 trench excavations revealed an urban fill thickness ranging from 0.4 to 3.6 m overlying a calcareous substratum. After ERT–EMI calibration, a two‐layer model was introduced into the one‐dimensional (1‐D) inversion of the EMI data for estimating the geometry of the urban fill layer across the study site. The EMI 1‐D inversion results indicated that the predicted urban fill thicknesses were consistent with 70% of the measured values (27 out of 40 excavation sites). Resistive ground, large 3‐D structures and the heterogeneity of urban fill affected the EMI and ERT measurements and increased the difficulty of estimating its spatial distribution. In this paper, we present a measurement protocol that can guide land‐use development and be reproduced to investigate brownfield sites. Highlights Urban soils are poorly characterized by localized investigations for environmental assessments. Spatial EMI data from an urban fill context were calibrated by ERT for thickness inversion. The ERT–EMI inversion reconstructed the urban fill thickness for 70% of the excavation points. Geophysical techniques can reduce uncertainties for site rehabilitation and land‐use development.

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Section: Discussionmentioning

confidence: 96%

Geometrical characterization of urban fill by integrating the multi‐receiver electromagnetic induction method and electrical resistivity tomography: A case study in Poitiers, France

Fraga

Schamper

Noël

et al. 2019

European J Soil Science

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“…Generally, in karstic aquifers, low resistivities can be associated with the high clay content (e.g., marlstone), or soils and weathered with a relatively high water content (Zhu et al 2011). Following previous studies (Robert et al 2011;Xu et al 2016;Bermejo et al 2017;Keshavarzi et al 2017) and an understanding of the characteristics of Chenqi watershed (e.g., brown clay and layered rock stratum), the resistivity distribution can be divided into three categories: (i) a soil layer, including Quaternary deposits (resistivity < 100 Ωm); (ii) extensively weathered rock (100 Ωm < resistivity < 400 Ωm); (iii) compact limestone (resistivity > 400 Ωm). Although this may be somewhat simplistic, it helps identify common features (at least based on their geoelectrical properties).…”

Section: Resistivity Along the Main Valley Channelmentioning

confidence: 95%

“…Therefore, low resistivity features are not necessarily associated with high hydraulic conductivity. The magnitude of resistivity contrasts can be site-specific due to other contributing factors (e.g., Robert et al 2011;Xu et al 2016;Bermejo et al 2017;McCormack et al 2017;Keshavarzi et al 2017), highlighting a limitation of using electrical geophysics in isolation of other observations. Electrical resistivity tomography is typically used to derive 2D images of the subsurface, i.e., it is assumed that resistivity does not vary in the strike direction (normal to the ERT survey line).…”

Section: Introductionmentioning

confidence: 99%

Characterization of karst structures using quasi-3D electrical resistivity tomography

et al. 2019

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Karst is characteristically complex, hydrogeologically, due to a high degree of heterogeneity, which is often typified by specific features, for example, cavities and sinkholes, embedded in a landscape with significant spatial variability of weathering. Characterization of such heterogeneity is challenging with conventional hydrogeological methods, however, geophysical tools offer the potential to gain insight into key features that control the hydrological function of a karst aquifer. Electrical resistivity tomography (ERT) is recognized as the most effective technique for mapping karstic features. This method is typically carried out along transects to reveal 2D models of resistivity variability. However, karstic systems are rarely 2D in nature. In this study, ERT is employed in valley and hillslope regions of a karst critical zone observatory (Chenqi watershed, Guizhou province, China), using a quasi-3D approach. The results from the extensive geophysical surveys show that there is a strong association between resistivity anomalies and known karstic features. They highlight the significance of a marlstone layer in channeling spring flow in the catchment and confining deeper groundwater flow, evidenced by, for example, localized artesian conditions in observation wells. Our results highlight the need to analyze and interpret geophysical data in a threedimensional manner in such highly heterogeneous karstic environments, and the value of combining geological and hydrogeological data with geophysical models to help improve our understanding of the hydrological function of a karst system.

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“…Nonetheless, ERT results interpretation can be used as a posterior validation tool for conduit geometries and more broadly the groundwater flow path. This point may constitute an open question for further investigations about hydrogeophysics since recent studies highlighted successfully applied geophysics applications for karst features detection [71][72][73].…”

Section: Discussionmentioning

confidence: 99%

Coupling SKS and SWMM to Solve the Inverse Problem Based on Artificial Tracer Tests in Karstic Aquifers

Sivelle

Renard

Labat

2020

Water

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Artificial tracer tests constitute one of the most powerful tools to investigate solute transport in conduit-dominated karstic aquifers. One can retrieve information about the internal structure of the aquifer directly by a careful analysis of the residence time distribution (RTD). Moreover, recent studies have shown the strong dependence of solute transport in karstic aquifers on boundary conditions. Information from artificial tracer tests leads us to propose a hypothesis about the internal structure of the aquifers and the effect of the boundary conditions (mainly high or low water level). So, a multi-tracer test calibration of a model appeared to be more consistent in identifying the effects of changes to the boundary conditions and to take into consideration their effects on solute transport. In this study, we proposed to run the inverse problem based on artificial tracer tests with a numerical procedure composed of the following three main steps: (1) conduit network geometries were simulated using a pseudo-genetic algorithm; (2) the hypothesis about boundary conditions was imposed in the simulated conduit networks; and (3) flow and solute transport were simulated. Then, using a trial-and-error procedure, the simulated RTDs were compared to the observed RTD on a large range of simulations, allowing identification of the conduit geometries and boundary conditions that better honor the field data. This constitutes a new approach to better constrain inverse problems using a multi-tracer test calibration including transient flow.

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2D and 3D ERT imaging for identifying karst morphologies in the archaeological sites of Gran Dolina and Galería Complex (Sierra de Atapuerca, Burgos, Spain)

Cited by 25 publications

References 41 publications

Geometrical characterization of urban fill by integrating the multi‐receiver electromagnetic induction method and electrical resistivity tomography: A case study in Poitiers, France

Geometrical characterization of urban fill by integrating the multi‐receiver electromagnetic induction method and electrical resistivity tomography: A case study in Poitiers, France

Characterization of karst structures using quasi-3D electrical resistivity tomography

Coupling SKS and SWMM to Solve the Inverse Problem Based on Artificial Tracer Tests in Karstic Aquifers

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