scholarly journals Electrical Resistivity Tomography (ERT) for the Investigation of Erosion site in Oredide Village, Auchi in Etsako West LGA of Edo State, Southern Nigeria

2021 ◽  
Vol 25 (5) ◽  
pp. 887-891
Author(s):  
D.A Babaiwa ◽  
O.J. Airen
Keyword(s):  
Electrical Resistivity Tomography ◽  
Electrode Spacing ◽  
High Resistivity ◽  
Depth Range ◽  
Resistivity Structure ◽  
Resistivity Tomography ◽  
Near Surface ◽  
The Third ◽  
Value Range ◽  
Edo State

The Dipole –Dipole array was used for Constant Separation Traversing (CST) to investigate subsurface lithology in Oredide village, Auchi, Edo state with a view to determining the vulnerability or otherwise of the menace of erosion in the area. All the traverses were carried out with electrode spacing of 10 m with a spread of 200 m. The data was obtained using Pasi terrameter (16-GL) and processed with the Dipro software. The results revealed that the subsurface is underlain by the topsoil, lateritic sand, sand and sandstone. 2D results indicate topsoil with resistivity value range of 309 to 40130 Ωm within the depth range of 0 to 5 m. The second layer corresponds to sandy, lateritic sand, sand and sandstone having resistivity values ranging from 2186 to 60350 Ωm to a depth of 10.0 m. The third layer has resistivity values indicating lateritic sand, sand and sandstone layer with resistivity values ranging from 2186 to 60350 within the depth of 20 m. The fourth layer connotes lateritic sand, sand and sandstone to a depth of 30 m. The fifth horizon has resistivity values in the range of 585.2 to 35732.4 Ωm which is representative of sand and sandstone.The maximum depth imaged was 47.7 m.The inverted 2-D resistivity structure shows high resistivity distribution near-surface >1000 Ωm, which are indications of vulnerabilities to erosion in the study area with depth of scouring being 15 m.

scholarly journals Exploring the regolith with electrical resistivity tomography in largescale surveys: electrode spacing related issues and possibility

2020 ◽  
Author(s):  
Laurent Gourdol ◽  
Rémi Clément ◽  
Jérôme Juilleret ◽  
Laurent Pfister ◽  
Christophe Hissler
Keyword(s):  
Electrical Resistivity ◽  
Apparent Resistivity ◽  
Large Scale ◽  
Electrical Resistivity Tomography ◽  
Subsurface Layer ◽  
Electrode Spacing ◽  
High Resistivity ◽  
Constant Thickness ◽  
Resistivity Tomography

Abstract. Within the Critical Zone, regolith plays a key role in the fundamental hydrological functions of water collection, storage, mixing and release. Electrical Resistivity Tomography (ERT) is recognized as a remarkable tool for characterizing the geometry and properties of the regolith, overcoming limitations inherent to conventional borehole-based investigations. For exploring shallow layers, a small electrode spacing (ES) will provide a denser set of apparent resistivity measurements of the subsurface. As this option is cumbersome and time-consuming, smaller ES – albeit offering poorer shallow apparent resistivity data – are often preferred for large horizontal ERT surveys. To investigate the negative trade-off between larger ES and reduced accuracy of the inverted ERT images for shallow layers, we use a set of synthetic conductive/resistive/conductive three-layered soil–saprock/saprolite–bedrock models in combination with a reference field dataset. Our results suggest that an increase in ES causes a deterioration of the accuracy of the inverted ERT images in terms of both resistivity distribution and interface delineation and, most importantly, that this degradation increases sharply when the ES exceeds the thickness of the top subsurface layer. This finding, which is obvious for the characterization of shallow layers, is also relevant even when solely aiming for the characterization of deeper layers. We show that an oversized ES leads to overestimations of depth to bedrock and that this overestimation is even more important for subsurface structures with high resistivity contrast. To overcome this limitation, we propose adding interpolated levels of surficial apparent resistivity relying on a limited number of ERT profiles with a smaller ES. We demonstrate that our protocol significantly improves the accuracy of ERT profiles when using large ES, provided that the top layer has a rather constant thickness and resistivity. For the specific case of large-scale ERT surveys the proposed upgrading procedure is cost-effective in comparison to protocols based on small ES.

scholarly journals Exploring the regolith with electrical resistivity tomography in large-scale surveys: electrode spacing-related issues and possibility

2021 ◽  
Vol 25 (4) ◽  
pp. 1785-1812
Author(s):  
Laurent Gourdol ◽  
Rémi Clément ◽  
Jérôme Juilleret ◽  
Laurent Pfister ◽  
Christophe Hissler
Keyword(s):  
Electrical Resistivity ◽  
Apparent Resistivity ◽  
Large Scale ◽  
Electrical Resistivity Tomography ◽  
Subsurface Layer ◽  
Electrode Spacing ◽  
High Resistivity ◽  
Constant Thickness ◽  
Resistivity Tomography

Abstract. Within the critical zone, regolith plays a key role in the fundamental hydrological functions of water collection, storage, mixing and release. Electrical resistivity tomography (ERT) is recognized as a remarkable tool for characterizing the geometry and properties of the regolith, overcoming limitations inherent to conventional borehole-based investigations. For exploring shallow layers, a small electrode spacing (ES) will provide a denser set of apparent resistivity measurements of the subsurface. As this option is cumbersome and time-consuming, larger ES – albeit offering poorer shallow apparent resistivity data – is often preferred for large horizontal ERT surveys. To investigate the negative trade-off between larger ES and reduced accuracy of the inverted ERT images for shallow layers, we use a set of synthetic “conductive–resistive–conductive” three-layered soil–saprock/saprolite–bedrock models in combination with a reference field dataset. Our results suggest that an increase in ES causes a deterioration of the accuracy of the inverted ERT images in terms of both resistivity distribution and interface delineation and, most importantly, that this degradation increases sharply when the ES exceeds the thickness of the top subsurface layer. This finding, which is obvious for the characterization of shallow layers, is also relevant even when solely aiming for the characterization of deeper layers. We show that an oversized ES leads to overestimations of depth to bedrock and that this overestimation is even more important for subsurface structures with high resistivity contrast. To overcome this limitation, we propose adding interpolated levels of surficial apparent resistivity relying on a limited number of ERT profiles with a smaller ES. We demonstrate that our protocol significantly improves the accuracy of ERT profiles when using large ES, provided that the top layer has a rather constant thickness and resistivity. For the specific case of large-scale ERT surveys the proposed upgrading procedure is cost-effective in comparison to protocols based on small ES.

scholarly journals Determination of dipping contacts using electrical resistivity tomography

2012 ◽  
Vol 42 (2) ◽  
pp. 161-180
Author(s):  
René Putiška ◽  
Ivan Dostál ◽  
David Kušnirák
Keyword(s):  
Electrical Resistivity ◽  
Electrical Resistivity Tomography ◽  
Image Resolution ◽  
High Resistivity ◽  
Depth Range ◽  
Electrode Arrays ◽  
Resistivity Tomography ◽  
Imaging Geometry ◽  
Lithostratigraphic Units

Determination of dipping contacts using electrical resistivity tomographyGenerally, all electrode arrays are able to delineate the contact of two lithostratigraphic units especially with very high resistivity contrast. However, the image resolution for the location of vertical and dipping structures is different. The responses of dipole-dipole (DD), Wenner alpha (WA), Schlumberger (SCH) and combined pole-dipole (PD) arrays have been computed using the finite difference method. Comparison of the responses indicates that: (1) The dipole-dipole array usually gives the best resolution and is the most detailed method especially for the detection of vertical structures. This array has shown the best resolution to recognize the geometrical characterisation of the fault. (2) The pole-dipole has shown the second best result in our test. The PD is an effective method for detection of vertical structures with a high depth range, but the deepest parts are deformed. (3) Wenner alpha shows a low resolution, inconvenient for detailed investigation of dip structures. (4) The Schlumberger array gives a good and sharp resolution to assess the contact between two lithological units but gives poor result for imaging geometry of dipping contact.

Decennial multi-approach monitoring of thermo-hydro-mechanical processes, Kammstollen outdoor laboratory, Zugspitze (Germany)

2021 ◽  
Author(s):  
Riccardo Scandroglio ◽  
Till Rehm ◽  
Jonas K. Limbrock ◽  
Andreas Kemna ◽  
Markus Heinze ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Electrical Resistivity Tomography ◽  
Environmental Research ◽  
Permafrost Degradation ◽  
Earth Surface ◽  
Data Set ◽  
Resistivity Tomography ◽  
Near Surface ◽  
Permafrost Rock ◽  
Austrian Alps

<p>The warming of alpine bedrock permafrost in the last three decades and consequent reduction of frozen areas has been well documented. Its consequences like slope stability reduction put humans and infrastructures at high risk. 2020 in particular was the warmest year on record at 3000m a.s.l. embedded in the warmest decade.</p><p>Recently, the development of electrical resistivity tomography (ERT) as standard technique for quantitative permafrost investigation allows extended monitoring of this hazard even allowing including quantitative 4D monitoring strategies (Scandroglio et al., in review). Nevertheless thermo-hydro-mechanical dynamics of steep bedrock slopes cannot be totally explained by a single measurement technique and therefore multi-approach setups are necessary in the field to record external forcing and improve the deciphering of internal responses.</p><p>The Zugspitze Kammstollen is a 850m long tunnel located between 2660 and 2780m a.s.l., a few decameters under the mountain ridge. First ERT monitoring was conducted in 2007 (Krautblatter et al., 2010) and has been followed by more than one decade of intensive field work. This has led to the collection of a unique multi-approach data set of still unpublished data. Continuous logging of environmental parameters such as rock/air temperatures and water infiltration through joints as well as a dedicated thermal model (Schröder and Krautblatter, in review) provide important additional knowledge on bedrock internal dynamics. Summer ERT and seismic refraction tomography surveys with manual and automated joints’ displacement measurements on the ridge offer information on external controls, complemented by three weather stations and a 44m long borehole within 1km from the tunnel.</p><p>Year-round access to the area enables uninterrupted monitoring and maintenance of instruments for reliable data collection. “Precisely controlled natural conditions”, restricted access for researchers only and logistical support by Environmental Research Station Schneefernerhaus, make this tunnel particularly attractive for developing benchmark experiments. Some examples are the design of induced polarization monitoring, the analysis of tunnel spring water for isotopes investigation, and the multi-annual mass monitoring by means of relative gravimetry.</p><p>Here, we present the recently modernized layout of the outdoor laboratory with the latest monitoring results, opening a discussion on further possible approaches of this extensive multi-approach data set, aiming at understanding not only permafrost thermal evolution but also the connected thermo-hydro-mechanical processes.</p><p> </p><p> </p><p>Krautblatter, M. et al. (2010) ‘Temperature-calibrated imaging of seasonal changes in permafrost rock walls by quantitative electrical resistivity tomography (Zugspitze, German/Austrian Alps)’, Journal of Geophysical Research: Earth Surface, 115(2), pp. 1–15. doi: 10.1029/2008JF001209.</p><p>Scandroglio, R. et al. (in review) ‘4D-Quantification of alpine permafrost degradation in steep rock walls using a laboratory-calibrated ERT approach (in review)’, Near Surface Geophysics.</p><p>Schröder, T. and Krautblatter, M. (in review) ‘A high-resolution multi-phase thermo-geophysical model to verify long-term electrical resistivity tomography monitoring in alpine permafrost rock walls (Zugspitze, German/Austrian Alps) (submitted)’, Earth Surface Processes and Landforms.</p>

scholarly journals CONTRIBUTION OF DEEP ELECTRICAL RESISTIVITY TOMOGRAPHY TECHNIQUE TO HYDROGEOLOGICAL STUDIES: CASES FROM AREAS IN KAVALA (NORTH GREECE)

2017 ◽  
Vol 43 (4) ◽  
pp. 1962
Author(s):  
G. Vargemezis ◽  
P. Tsourlos ◽  
I. Mertzanides
Keyword(s):  
Electrical Resistivity ◽  
Electrical Resistivity Tomography ◽  
Geological Structure ◽  
Resistivity Tomography ◽  
Near Surface ◽  
Resistivity Method ◽  
Area Of Interest ◽  
Vertical Electric Sounding ◽  
Hydrogeological Studies ◽  
2D And 3D

The most common geophysical method widely used in hydrogeological surveys concerning deep investigations (150-300m of depth) is the resistivity method and particularly the Vertical Electric Sounding (VES) using the Schlumberger array. VES interpretations assume 1D geoelectrical structure yet it is obvious that such an interpretation assumption is not valid in many cases where 2D and 3D geological features exist. In such cases the application of geoelectrical techniques which can provide both vertical and lateral information concerning the resistivity variations is required. Techniques such as the electrical resistivity tomography, mostly used for the 2D and 3D geoelectrical mapping of near surface applications can be adapted to be used for larger investigation depths provided that modified equipment (viz. cables) is used. In the present paper, the application of deep electrical resistivity tomography (ERT) techniques is applied. ERT array of 21 electrodes, at a distance of 50 meters between them (total length 1000 meters) has been used in several studied areas located in the prefecture of Kavala (North Greece). In several cases near surface structure has been compared with VLF data. The aim of the survey was to study in detail the geological-hydrogeological structure the area of interest in order to suggest the best location for the construction of hydrowells with the most promising results. The 2D images of the geological structure down to the depth of at least 200 meters allowed the better understanding of the behaviour of layered geological formations, since in several cases resistivity values have been calibrated with data from pre-existing boreholes.

scholarly journals Application of electric resistivity tomography for investigation of geological situation closed to railways

2019 ◽  
Vol 265 ◽  
pp. 03005
Author(s):  
Dmitriy Gorbach ◽  
Valeriya Yakimenko ◽  
Olga Konovalova
Keyword(s):  
Electrical Resistivity ◽  
Electrical Resistivity Tomography ◽  
Electric Resistivity ◽  
Practical Work ◽  
Surface Zone ◽  
Two Dimensional ◽  
Resistivity Tomography ◽  
Near Surface ◽  
Geological Situation ◽  
Engineering Geophysics

The paper reviews methods of engineering geophysics which can be applied to sections of railway tracks. The method of electrical resistivity tomography is used to study the properties of the geological situation under an engineering structure. In the course of practical work, two-dimensional geoelectric sections were obtained. Interpretation of the sections allowed to understand the structure of the near-surface zone.

scholarly journals Combining Electrical Resistivity Tomography and Satellite Images for Improving Evapotranspiration Estimates of Citrus Orchards

2019 ◽  
Vol 11 (4) ◽  
pp. 373 ◽  
Author(s):  
Daniela Vanella ◽  
Juan Ramírez-Cuesta ◽  
Diego Intrigliolo ◽  
Simona Consoli
Keyword(s):  
Electrical Resistivity ◽  
Water Stress ◽  
Soil Water ◽  
Electrical Resistivity Tomography ◽  
New Technologies ◽  
Water Status ◽  
Irrigation Season ◽  
Resistivity Tomography ◽  
Near Surface ◽  
Near Surface Geophysics

An adjusted satellite-based model was proposed with the aim of improving spatially distributed evapotranspiration (ET) estimates under plant water stress conditions. Remote sensing data and near surface geophysics information, using electrical resistivity tomography (ERT), were used in a revised version of the original dual crop coefficient (Kc) FAO-56 approach. Sentinel 2-A imagery were used to compute vegetation indices (VIs) required for spatially estimating ET. The potentiality of the ERT technique was exploited for tracking the soil wetting distribution patterns during and after irrigation phases. The ERT-derived information helped to accurately estimate the wet exposed fraction (few) and therefore the water evaporated from the soil surface into the dual Kc FAO-56 approach. Results, validated by site-specific ET measurements (ETEC) obtained using the eddy covariance (EC) technique, showed that ERT-adjusted ET estimates (ETERT) were considerably reduced (15%) when compared with the original dual Kc FAO-56 approach (ETFAO), soil evaporation overestimation being the main reason for these discrepancies. Nevertheless, ETFAO and ETERT showed overestimations of 64% and 40% compared to ETEC. This is because both approaches determine ET under standard conditions without water limitation, whereas EC is able to determine ET even under soil water deficit conditions. From the comparison between ETEC and ETERT, the water stress coefficient was experimentally derived, reaching a mean value for the irrigation season of 0.74. The obtained results highlight how new technologies for soil water status monitoring can be incorporated for improving ET estimations, particularly under drip irrigation conditions.

Target-oriented optimized survey design and quantitative comparison for 3D electrical resistivity tomography

2020 ◽  
Author(s):  
Lincheng Jiang ◽  
Gang Tian ◽  
Bangbing Wang ◽  
Amr Abd El-Raouf
Keyword(s):  
Electrical Resistivity ◽  
Electrical Resistivity Tomography ◽  
Survey Design ◽  
Quantitative Comparison ◽  
Data Set ◽  
Resistivity Tomography ◽  
Near Surface ◽  
Target Set ◽  
Survey Designs

<p>In recent decades, geoelectrical methods have played a very important role in near-surface investigation. The most widely used of these methods is electrical resistivity tomography (ERT). Regardless of the forward and inversion algorithms used, the original data collected from a survey is the most important factor for quality of the resulted model. However, 3D electrical resistivity survey design continues to be based on data sets recorded using one or more of the standard electrode arrays. There is a recognized need for the 3D survey design to get better resolution using fewer data. Choosing suitable data from the comprehensive data set is a great approach. By reasonable selecting, better resolution can be obtained with fewer electrodes and measurements than conventional arrays. Previous research has demonstrated that the optimized survey design using the 'Compare R' method can give a nice performance.</p><p>This paper adds target-oriented selection and modified the original 'Compare R' method. The survey design should be focused on specific target areas, which need a priori information about the subsurface properties. We select electrodes and configurations as the target set by the comprehensive set firstly which meets the requirements of the target area. The number of measurements and electrodes is much less than the comprehensive set and the model resolution matrix takes less time to calculate. At the next step for rank, we calculate the sensitivity matrix of the target set only once and then calculate the contribution degree of each measurement separately from it. The time of iterative calculation of the resolution matrix when measurements set changing is less than the original method.</p><p>The traditional method of evaluating RMS is not appropriate for comparing the quality of collected data by different survey designs. SSIM (structural similarity index) gives more reliable measures of image similarity better than the RMS. The curves of SSIM values in three dimensions and the average SSIM are given as quantitative comparisons. Besides, the frequency of electrodes utilized given to guides on selecting the highest used electrodes. Finally, the curves of the average relative resolution S and the number of electrodes as the number of measurements increase are given, which proves the method works effectively.</p><p>The results show the significance of using target-oriented optimized survey design, as it selects fewer electrodes and arrays than the original CR method. Also, it produces better resolution than conventional arrays and takes less calculation time. 3D SSIM, frequency of electrodes used, the relationship between average relative resolution, number of electrodes and number of measurements, these quantitative comparison methods can effectively evaluate the data collected in various survey designs.</p>

scholarly journals Electrical resistivity tomography applied to geologic, hydrogeologic, and engineering investigations at a former waste-disposal site

Geophysics ◽  
2006 ◽  
Vol 71 (6) ◽  
pp. B231-B239 ◽  
Author(s):  
Jonathan E. Chambers ◽  
Oliver Kuras ◽  
Philip I. Meldrum ◽  
Richard D. Ogilvy ◽  
Jonathan Hollands
Keyword(s):  
Electrical Resistivity ◽  
Electrical Resistivity Tomography ◽  
Site Investigation ◽  
High Resistivity ◽  
Potential Zone ◽  
Resistivity Tomography ◽  
L2 Norm ◽  
Resistivity Model ◽  
2D And 3D ◽  
2D Resistivity

A former dolerite quarry and landfill site was investigated using 2D and 3D electrical resistivity tomography (ERT), with the aims of determining buried quarry geometry, mapping bedrock contamination arising from the landfill, and characterizing site geology. Resistivity data were collected from a network of intersecting survey lines using a Wenner-based array configuration. Inversion of the data was carried out using 2D and 3D regularized least-squares optimization methods with robust (L1-norm) model constraints. For this site, where high resistivity contrasts were present, robust model constraints produced a more accurate recovery of subsurface structures when compared to the use of smooth (L2-norm) constraints. Integrated 3D spatial analysis of the ERT and conventional site investigation data proved in this case a highly effective means of characterizing the landfill and its environs. The 3D resistivity model was successfully used to confirm the position of the landfill boundaries, which appeared as electrically well-defined features that corresponded extremely closely to both historic maps and intrusive site investigation data. A potential zone of leachate migration from the landfill was identified from the electrical models; the location of this zone was consistent with the predicted direction of groundwater flow across the site. Unquarried areas of a dolerite sill were imaged as a resistive sheet-like feature, while the fault zone appeared in the 2D resistivity model as a dipping structure defined by contrasting bedrock resistivities.

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