Electrical Resistivity Survey Research Articles

A Comparison Between Schlumberger and Wenner Configurations in Delineating Subsurface Water Bearing Zones: A Case Study of Rawalakot Azad Jammu and Kashmir, Pakistan

The Schlumberger and Wenner Electrical Resistivity Survey techniques have been used in comparison for the determination of groundwater potential in District Rawalakot, Azad Jammu and Kashmir. The terameter SAS4000 with accessories was used for data acquisition. The data were processed by employing IPI2WIN software to determine the depth, thickness and true resistivity of the subsurface layers. The present study indicated the subsurface depth coverage of Schlumberger configuration is greater than Wenner configuration. The apparent resistivity maps using both Wenner and Schlumberger techniques at the same locations have been prepared at 3m, 4m, 9m, 10m, 27m, 30m, 50m, 51m, 100m, and 150m depths respectively for groundwater assessment. The differences in resistivity contour closures, in both types of maps, arise due to lateral variations of subsurface lithology. Longitudinal conductance, transverse resistance and anisotropic maps were also prepared. The different contour closures in the Wenner map were due to mixed lithology of alluvium with variable water contents. The subsurface geology i.e. clay, sandstone boulder clay, and dry sandy soil were interpreted which are in close agreement with the surface geology of the area. The aquifers of the project area are designated as confined and unconfined good water potential indicated by low values of resistivity. The water-bearing strata consist of sand, gravel, boulder clay and sandy clay.

Exploration of Shallow Geothermal Energy Aquifers by Using Electrical Resistivity Survey in Laki Range Jamshoro district Sindh, Pakistan

Geothermal water is increasingly used around the world for its exploitation. Bulk electrical resistivity differences can bring significant information on variation of subsurface geothermal aquifer characteristics. The electrical resistivity survey was carried out in Laki range in lower Indus basin in the study area to explore the subsurface geothermal aquifers. The Schlumberger electrode configuration with range from 2 m to 220 m depth was applied. Three prominent locations of hot springs were selected including Laki Shah Saddar, Lalbagh and Kai hot spring near Sehwan city. After processing resistivity image data, two hot water geothermal aquifers were delineated at Laki Shah Sadder hot springs. The depth of first aquifer was 56 m and its thickness 38 m in the limestones. The depth of second aquifer of 190 m and with thickness of 96 m hosted in limestone. In Lalbagh hot springs two geothermal aquifers were delineated on the basis of apparent resistivity contrast, the depth of first aquifer zone in sandstone was in sandstone 15 m and thickness 12 m, while the depth of second aquifer was 61m and thickness was 35m. In Kai hot springs two hot water geothermal aquifers were delineated. The depth of first geothermal aquifer was 21m and thickness was 18 m and the depth of second aquifer was 105 m and thickness was 61m present in sandstone lithology. Present work demonstrates the capability of electrical resistivity images to study the potential of geothermal energy in shallow aquifers. These outcomes could potentially lead to a number of practical applications, such as the monitoring or the design of shallow geothermal systems.

Lateral Constrained Inversion of DC-Resistivity Data Observed at the Area North of Tenth of Ramadan City, Egypt for Groundwater Exploration

In the arid climate area north of Tenth of Ramadan City, southeast of the Nile Delta, Egypt, it is necessary to search for additional water resources for sustainable developments such as agricultural and industrial activities. Thirty two vertical electrical soundings (VES) of a electrical resistivity (DC) survey were carried out along four main profiles by using the Schlumberger array with electrode distances (AB/2) up to 500 m, to explore the shallow Pleistocene groundwater aquifer. The collected data was interpreted by a one-dimensional laterally constrained inversion (1D-LCI) and two-dimensional inversion algorithms to derive a best fit layered-earth resistivity model. The derived resistivity sections are geologically well interpreted based on information taken from the available water boreholes (P2-Well and P3-Well). The lateral constraints are part of the inversion where all data sets are inverted simultaneously, and consequently the output models are balanced between the constraints and the data-model fit. The 1D-LCI offers good analysis of the model parameters, which was successfully used to characterize a zone of groundwater aquifer, as it produces a laterally smooth model with sharp layer boundaries. The 1D-LCI inversion results show that the study area is subdivided into five geo-electrical layers of varied resistivity and thickness. In particular, the resistivity values of the last layer range between 9.3 and 110 Ωm representing the existing shallow Pleistocene aquifer located at depths between 134.5 and 118.4 m. Such results are tied and confirmed well with the results of the 2D inversion of the DC data. It reveals three interpreted geo-electric layers along the four profiles and shows that the area is affected by some normal faults striking nearly in the E–W direction. The very low resistivities of the groundwater aquifer beneath the agricultural part of the survey area probably indicates contamination due to the possible effect of irrigation operated in the cultivated lowlands. The results obtained could help the stakeholder to find additional information about the ground water aquifers in the newly reclaimed arid area and possible locations of new sites for drilling new water wells as additional water resources.

Delineation of Lithological Formation in Bukit Merah, Semanggol, Perak Using Groundwater Modelling Software

The knowledge of lithological formation is important to determine the potential aquifer for water resources management. This study aims to delineate the lithological formation of Bukit Merah, Semanggol using geological data. The preparation of lithological formation in the study was based on several factors such as electrical resistivity survey data, available well lithologies, geological map, and geological-related studies in the study area. The Electrical Resistivity Tomography (ERT) profile produced from the resistivity survey was interpreted based on previous studies to determine the subsurface materials on the location. The estimation of soil lithology for the remaining wells was done to generate the overall subsoil pattern in the study area. A total of 15 types of soil were classified to represent the actual lithology in the study area. The simplification of the actual lithology was carried out based on rocks and soils group. The elevation of the ground surface and each soil layer were imported into Visual MODFLOW software, then the interpolation of elevation points was done. Two interpolators; Kriging and Natural Neighbouring were used to generate ground surface and model layers similar to the topography in the study area. As a result, it has been identified that the study areas consist of 4 main layers of lithological formation which are unconsolidated deposit, sedimentary, metamorphic, and granite. The upper layer is dominated by unconsolidated with a maximum thickness of about 150 m in the coastal area. Hence, it is concluded that the unconsolidated deposit layer in Bukit Merah is highly potential with groundwater resources in the alluvium aquifer at the upper layer which has the potential to be developed for purpose of irrigation in a paddy field in the Kerian area.

Application of 3D Electrical Resistivity Tomography in the Yeoncheon Titanomagnetite Deposit, South Korea

The Yeoncheon titanomagnetite deposit formed by Precambrian magma differentiation is located in Gyeonggi-do, South Korea. Our team conducted an airborne magnetic survey for multiscale mineral exploration and then selected a promising survey area. An electrical resistivity survey was carried out in the potential area to image subsurface structure. Because ore minerals are mainly distributed in gabbro monzodiorite rather than quartz monzodiorite, we applied three-dimensional inversion of electrical resistivity tomography (ERT) data to identify lithology boundaries related to magma differentiation. The resistivity criterion distinguishing the lithologies of gabbro and quartz monzodiorite was determined from laboratory resistivity experimental results performed on drilling cores. The selected region for gabbro monzodiorite extends to the northeast direction, which is consistent with the geology map, magnetic anomaly, and drilling data. The inversion results of ERT can help in selecting the location of geophysical survey or drilling.

Geophysical surveys integrated with rainfall data analysis for the study of soil piping phenomena occurred in a densely urbanized area in eastern Sicily

The occurrence of strong and abrupt rainfall, together with a wrong land use planning and an uncontrolled urban development, can constitute a risk for infrastructure and population. The water flow in the subsoil, under certain conditions, may cause underground cavities formation. This phenomena known as soil piping can evolve and generate the surface collapse. It is clear that such phenomena in densely urbanized areas represent an unpredictable and consistent risk factor, which can interfere with social activities. In this study a multidisciplinary approach aimed to obtain useful information for the mitigation of the risks associated with the occurrence of soil piping phenomena in urban areas has been developed. This approach is aimed at defining the causes of sudden soil subsidence events, as well as the definition of the extension and possible evolution of these instability areas. The information obtained from rainfall data analysis, together with a study of the morphological, geological and hydrogeological characteristics, have allowed us to evaluate the causes that have led to the formation of soil pipes. Furthermore, performance of 3D electrical resistivity surveys in the area affected by the instability have allowed us to estimate their extension in the subsoil and identifying the presence of further areas susceptible to instability.

Rapid characterisation of landslide heterogeneity using unsupervised classification of electrical resistivity and seismic refraction surveys

The characterisation of the subsurface of a landslide is a critical step in developing ground models that inform planned mitigation measures, remediation works or future early-warning of instability. When a landslide failure may be imminent, the time pressures on producing such models may be great. Geoelectrical and seismic geophysical surveys are able to rapidly acquire volumetric data across large areas of the subsurface at the slope-scale. However, analysis of the individual model derived from each survey is typically undertaken in isolation, and a robust, accurate interpretation is highly dependent on the experience and skills of the operator. We demonstrate a machine learning process for constructing a rapid reconnaissance ground model, by integrating several sources of geophysical data in to a single ground model in a rapid and objective manner. Firstly, we use topographic data acquired by a UAV survey to co-locate three geophysical surveys of the Hollin Hill Landslide Observatory in the UK. The data are inverted using a joint 2D mesh, resulting in a set of co-located models of resistivity, P-wave velocity and S-wave velocity. Secondly, we analyse the relationships and trends present between the variables for each point in the mesh (resistivity, P-wave velocity, S-wave velocity, depth) to identify correlations. Thirdly, we use a Gaussian Mixture Model (GMM), a form of unsupervised machine learning, to classify the geophysical data into cluster groups with similar ranges and trends in measurements. The resulting model created from probabilistically assigning each subsurface point to a cluster group characterises the heterogeneity of landslide materials based on their geophysical properties, identifying the major subsurface discontinuities at the site. Finally, we compare the results of the cluster groups to intrusive borehole data, which show good agreement with the spatial variations in lithology. We demonstrate the applicability of integrated geophysical surveys coupled with simple unsupervised machine learning for producing rapid reconnaissance ground models in time-critical situations with minimal prior knowledge about the subsurface.

Geological controls on brine discharge in Itumbula Salt Dam within the Rukwa Rift in Momba District, Tanzania

The Itumbula salt dam of the Rukwa Rift Basin is a depression formed through extraction of spring-derived salt crystals. Brine yield by springs which is the primary cause of significant amounts of salt in the dam required further geological investigations to understand yield controls. In this study, detailed field geological investigations in the salt dam and its surroundings were conducted to ascertain brine discharge controls. These included documentation of lithology and surface manifestations of brine deposition. Geophysical methods (i.e. magnetic and electric surveys) for studying geologic structures associated with brine deposits, and laboratory analysis of cations and anions (e.g. chlorides, bicarbonates or sulphates) essential to characterize composition of waters were also performed. The information on the springs discharge rate was retrieved from the previous studies. The magnetic profile revealed a very low magnetic anomaly across the salt dam, trending NW to SE direction, which is interpreted to be the main structure that controls fluid movements in the dam. Electric resistivity survey results delineated a low resistivity body in the central part of the dam interpreted as porous formation with saline water. Hydro-chemistry of the hot spring brines indicated high levels of sodium and chloride ions contents than magnesium, calcium, potassium, sulphate, and carbonate and bicarbonate ions, interpreted to be mature water with minimal water mixing. The structurally controlled brines of approximately 2.5 kg/s are discharged in the study area.
 Keywords: Geologic Structures, Brine, Salt Production, Momba, Rukwa Basin.

Impact Assessment of Dumpsite Effect on Groundwater Quality Using Geophysical and Geochemical Techniques in Balogun Iwaya, Lagos Southwestern Nigeria

Waste disposal and management is a challenge in developing countries and has great influence on the groundwater quality. This research aimed at assessing the impact of leachate on nearby wells within the vicinity of active dumpsite in Yaba, Lagos, Nigeria. Four vertical electrical sounding and four electrical resistivity tomography using Schlumberger and Wenner electrode configurations respectively were carried out at the dumpsite. Physicochemical analysis of water samples from neighbouring wells were also conducted. The geo-electric curve showed four different subsurface layers. The electrical resistivity surveys revealed low resistivity values of s uspected leachate between 1.77 and 39.1 Ωm at a maximum depth of 20.8 m from the subsurface. The leachate polluted area is characterized by low resistivity values ranging from 1 to 10 Ωm, the thickness ranged from 0.5 to 9.2 m and the dir ection of leachate flow is from the northeast to southwest of the canal. The physicochemical analysis revealed that SO42- (70 - 89 mg/l) and Cl- (115.7 - 190.5 mg/l) have values within the World Health Organization (WHO) permissible limit. The pH (5.08 - 6.07), Electrical conductivity (774-1028 μS /cm) and the total dissolved solids values fall below WHO limit. The impact assessment of dumpsite effect revealed that the groundwater quality was affected by the leachate flow.

Potential Groundwater Exploration in Use of 2-D Electrical Resistivity Tomography (ERT) Techniques at the Department of Agriculture Kelantan Research and Developmental Platform Padang Raja Kelantan

2-D electrical resistivity has been a proper investigation survey for determination of subsurface geophysical in describing the complex features geology profile. In this study, an electrical resistivity survey was conducted at paddy cultivation area located in Melor, Kelantan, Malaysia. Since the end plot of paddy field experiences water scarcity especially during dry season, there is a need to find other alternative water source. The study was conducted on 1st and 2nd February 2020 to identify zone area of groundwater for Melor, Kelantan. Four resistivity lines using Induced Polarization (IP) and 2-D Electrical Resistivity Imaging Technique were conducted using a set of ABEM Terrameter SAS4000. Short resistivity survey was applied to gained detail of subsurface formation near the ground, while the longer resistivity survey was applied to obtain deeper subsurface delineation. Measured data obtained was analyzed using RES2DINV software and result of contrast resistivity values was used to determine the geological structures, while the chargeability values were analyzed accordingly to determine area of expected potential groundwater zone. Results from the resistivity profiles show a range values of 0 Ωm to 50,000 Ωm with total maximum acquired depth of 65.6 m below ground surface. The chargeability profiles show a range values of 0 msec to 500 msec, that shows potential of groundwater zone area lies at 0 to 4 msec. It was found that at a depth of 60 to 75 m, 30 m from center of Profile B was suitable for a production well which was expected to be a potential area for groundwater zone.

Engineering Geophysical Investigation of Road Failure in a Basement Complex Terrain, Southwestern Nigeria

Geoelectrical and geotechnical investigations were conducted to determine factors responsible for pavement failure in some segments of Adebayo Alao-Akala road in Ibadan, southwestern Nigeria. The geoelectrical investigation employed Schlumberger vertical electrical sounding conducted at fifteen stations occupied along two failed segments and one stable segment of the road, using station spacing of 25 m and maximum electrode spread of 100 m. 2D electrical resistivity survey was also conducted using the dipole-dipole electrode array with electrode spacing, a, of 1 m and expansion factor, n varied from 1 to 5 m. The VES data were interpreted quantitatively by partial curve matching and computer iteration technique and geoelectric sections were generated while 2D resistivity structures of the subsurface were produced from the inverted 2D resistivity data. The geotechnical investigation involved Grain size distribution, Atterberg limits, Compaction and California Bearing Ratio tests conducted on subsoils collected beneath the segment. The failed segments are underlain by low-resistivity clayey subgrade of resistivity mostly less than 100Ωm while the stable segment overlies sandy clay/clayey sand mixture of relatively higher resistivity, ranging from 200Ωm to 530Ωm. The subsoils of the failed segments comprise high-plasticity sandy clay and sandy gravelly clay while those of the stable segment are medium plasticity sandy clayey gravel. The values of maximum dry density are 1.46 Mg/m3-1.73 Mg/m3, 1.71 Mg/m3-1.86 Mg/m3 and 1.75 Mg/m3-1.82 Mg/m3 respectively, with corresponding optimum moisture content of 7%-8%, 11%-20% and 10%-17% and California bearing ratio under soaked condition for 48 hours of 7%-8%, 17%-20% and 11%-17% respectively. The failure of the road pavement is attributable to the clayey nature of the subgrade, and poor drainage. The stable segment is underlain by excellent-to-good subgrade materials. Ingress of surface water into the clayey subgrade occasioned by poor drainage of run-off resulted in deformation of the road pavement in response to vehicular load.

Modelling the effect of geo-matrix conduction on the bulk and pore water resistivity in hydrogeological sedimentary beddings

Generally, the electrical method of geophysics is potentially valuable in typifying the subsurface conductivity and its surrounding medium. Sixteen datasets of 1-D electrical resistivity survey was integrated with 8 core samples, which were taken in the neighbourhood of eight of the sixteen VES datasets. The two sets of data were intertwined with geological and hydrogeological datasets to enhance the realization of unique results used in assessing the aquifer geo-matrix and pore water geo-resistivity in four counties in the coastal province of Akwa Ibom State, southern Nigeria. The current electrode separations of 1-D resistivity data were extended up to 300 m to ensure that the prolifically exploited water-bearing units were assessed. The VES data were manually and electronically modeled and each of them showed characteristic four geo-electric layers with KH, HK, KQ, HA and A group of curves. The core samples, which cut across the local Government Areas under survey, included sandy clay (12.5%), fine-grained sand (50.0%), medium-grained sand (12.5%) and coarse sand (25.0%). Bulk resistivities of water-bearing units and other primary geo-electrical indices were measured in all sixteen locations. However, in the eight aquifer core sample locations, water resistivities were measured in situ. The core samples were taken to the laboratory for measurements of fractional porosity and volumetric water content. The measured fractional porosity ranged from 0.189 to 0.267 with an average of 0.232, whilst volumetric water content varied from 0.23 to 0.31 with an average value of 0.268. The transmission coefficients were computed from volumetric water content and other parameters in the work. The values ranged from 0.4135 to 0.5612 with an average value of 0.4945. Fractional porosity was also modeled from field parameters and the results showed a good match with laboratory measurement as the root—mean square error was just 1.3%. Intrinsic specific resistance and conductivity of soil aquifer matrix were found to be $$3.333 \times 10^{3} \;\Omega {\text{m}}$$ and $$3.000 \times 10^{ - 4} \;{\text{Sm}}^{ - 1}$$ respectively. The study has provided useful information about the geo-electrical and geo-pore properties of the prolifically exploited aquifers in the study area. The aquifer parameter contour maps have been delineated and these, together with other parameter relations generated in this study could help in predicting the volumetric conductivity between pore water and the matrix texture of hydrogeological units in the study area and other areas with similar geology.

Parallel tunnel channels of the Huron-Erie Lobe of the Laurentide Ice Sheet: A variation of tunnel channels with implications on lobe history and subglacial meltwater dynamics

Newly available high resolution elevation data across North America and Europe have revealed previously unknown glacial landforms. This study focuses on the morphology and stratigraphy of a variation of tunnel channels with unique morphology that we have named parallel tunnel channels (PTCs). They are found in northeastern Indiana, northwestern Ohio, and southeastern Michigan, which were previously glaciated by the Huron-Erie Lobe (HEL) of the Laurentide Ice Sheet (LIS). PTCs are discontinuous, quasi-parallel pairs of depressions separated by a continuous central ridge that can extend upwards of 50 km, cross-cut multiple recessional moraines, and transition into standard tunnel channels. The PTCs range in width from 200 to 900 m, and the depressions range in width from 100 to 200 m and in depth from 3 to 10 m. Using water well logs and multiple electrical resistivity surveys, we determined that the stratigraphy beneath and surrounding the PTCs consists of a lower layer of sand and gravel (confined aquifer) and an upper layer of New Holland till, both of the Lagro Formation. A vibracore and multiple resistivity surveys reveal that depressions are filled with ~4 m of lacustrine sediment and occasionally are floored with gravel channel deposits. The depressions are erosional in origin, rather than a product of ice block melt-out and are cut into the upper surface of the New Holland till. We interpret the PTCs as subglacial, erosional landforms, similar to tunnel channels, which represent distinct pathways transporting subglacial meltwater from the interior to the ice margin. Identification of these landforms has several important implications for understanding the deglaciation of the HEL: 1) the major recessional moraines may not record the final deglaciation of the HEL (i.e., are palimpsest features); 2) a large portion of the HEL must have stagnated to preserve the subglacial landscape including the PTCs; and 3) the combined network of PTCs, tunnel channels, and proglacial spillways may represent a partially complete subglacial drainage network with distinct morphological changes as meltwater was transported from the interior to the margin of the HEL. An initial formational model is proposed for the formation of the PTCs by way of a supra- and/or subglacial lake draining through an ice-walled subglacial tunnel, but additional work is required to understand the distinct pattern of depressions observed.

Multisource data integration for groundwater prospecting in Precambrian shear zones, Espírito Santo State (Southeastern Brazil)

The Precambrian metamorphic rocks in the southern region of the Espírito Santo State(southeastern Brazil) is intercepted by ductile and brittle/ductile shear zones over which towns like Guaçuí, Marechal Floriano and Domingos Martins were established. In the years of 2014 to 2016 the Espírito Santo State faced the worst drought in the past 80 years. In situations like that, the only source of fresh water available is underground. Therefore, the purpose of this study was to integrate multisource data for groundwater prospecting and management. The study area comprises the central sectors of the Guaçuí and Batatal shear zones. Methodology involved the interpretation of stereo-pairs for the identification of lineaments, electrical resistivity surveys and geological fieldwork. The results were tentatively validated with available groundwater well production data. Six resistivity profiles with a total length of 2,400 m were surveyed and 15 outcrops were described across these structures. Results have shown that the structural framework of the shear zones is predominantly made of NW to NNW and NE to NNE-trending lineaments. The former is related to brittle tectonics and the latter coincides with the ductile Precambrian fabric of the crystalline basement rocks. A near-surface porous aquifer regarded to the regolith and recent unconsolidated sedimentary deposits presenting resistivity values < 1,372 Ohm.m and depths < 30 m have good potential for groundwater storage. However, results arenot conclusive about the hydrogeological significance of tectonic structures for groundwaterprospection in the study area.

Evaluation of the potential of refuse-derived fuel recovery in the open dump by resistivity survey prior to mining

Currently, there is no technique to characterise the waste composition that can be processed into refuse-derived fuel in the open dumpsite. This study’s objective is to investigate the feasibility of applying resistivity measurements to evaluate waste composition in the open dumpsite. Electrical resistivity surveys were performed in two open dumpsites. One hundred waste samples were collected from both sites to classify the composition. The relation between resistivity and waste composition was then studied. The result showed a high correlation between resistivity and the composition of plastic (r2 = 0.809), characterising the waste in the dumpsite. The waste with resistivity values range 0.1–80 Ωm, 80–250 Ω·m and above 250 Ωm have compositions of plastic equalling 25–35%, 30–45% and above 40%, respectively. This finding can be used as a guideline to characterise the waste composition before mining. The resistivity measurement provides a reliable result but is labour-intensive.

Spatio-Temporal Variation of Seawater Intrusion (SWI) inferred from geophysical methods as an ecological indicator; A case study from Dikili, NW İzmir, Turkey

Water resources are fundamental components of ecological life that must be maintained since they are at the risk of both pollution and depletion. Recently, one of the main factors threatening water resources is the groundwater salinization.In this study, electrical resistivity method via vertical electrical sounding (VES) technique and time-domain induced polarization (IP) method were applied on 34 points to show the electrical characteristic of the coastal area of Dikili district, NW İzmir, Turkey. Possible freshwater/seawater interface and the existence of the geothermal potential were successfully elucidated by a joint interpretation of the results inferred from both methods. Four different types of water resources were classified according to the apparent resistivity and chargeability values, which is freshwater (<10 Ω.m and 10–620 msec.), saline water (<0.6 Ω.m and 600 > msec.), geothermal water (8–150 Ω.m and > 14,000 msec.) and mixed water (0.5–60 Ω.m and 200–1600 msec.).To show the temporal and spatial change of the geo-electrical properties in the subsurface, geoelectrical sections obtained from 1D and 2D inversion of resistivity data were compared with those of an electrical resistivity survey conducted on 119 VES points in 1978 by the General Directorate of State Hydraulic Works (DSI in Turkish acronym).The results of this study highlight significant areas where the resistivity values are lower than <0.6 Ωm as this implies evidence of presumable seawater intrusion (SWI), while previous resistivity values below 10 Ωm denote salt intrusion restricted in narrow areas. A comparison of the two resistivity sections indicates evidence of SWI into the fresh groundwater that spatially has been extended as 20 km2. We suggest streams that are cut by faults and anthropogenic effects, instead of rising sea level, likely govern the salinization in the district of Dikili during a short time period of 40 years.

Pore resistivity variation by Resistivity imaging technique in sedimentary part of main Gadilam river basin, Cuddalore District, Tamil Nadu, India

Electrical resistivity is the only property of physics which give information of subsurface moisture content in the formation, Hence geophysical electrical resistivity survey was carried out to investigate the nature of shallow subsurface formations and geological contact in the main Gadilam river basin of Cuddalore District in Tamil Nadu. Twenty-seven vertical electrical soundings (VES) were conducted by Schlumberger configuration in the basin. Data is interpreted by curve matching techniques using IPI2 WIN software, layer parameters like apparent resistivity (?a) and thickness (h) interpretation were exported to Geographic Information System (GIS). Interpretation distinguishes three major geoelectric layers like topsoil, sandy clay layer, clayey sand layer along the contact zone in the basin. Interpreted VES sounding curves are mostly four-layer cases of QH, H, HA and KH type. Investigation demarcates lithology of subsurface and hydrogeological set up by employing maximum possible electrode sounding to infer saline water and freshwater occurrence based on resistivity signals. Zone of groundwater potential map was prepared with the combination of resistivity (?= ?1+ ?2+ ?3+ ?4) and corresponding thickness (T= T1+T2+T3+T4). High resistivity value of &gt;200 ? m and low resistivity value of &lt;10 ? m show the occurrence of alkaline and saline water within the formation aquifers as a result of possible rock water interaction and saline water dissolution. Four-layer resistivity cases from the matched curve (namely KH, AH, QA, and KA type) show the resistivity distribution/variation. It separates the freshwater depth wish from 1 to 140 ? m in fluvial sediments. Flood basin, sandstone and clay layer with low resistivity value of 3.16 - 7.5 ? m indicates contact with saline and freshwater aquifer. The Iso – resistivity map delineates saline water and freshwater zones with in the fourth layer cases in the same locations to indicate the irrational way of abstracting groundwater, resulting in saltwater ingress.

Characterization of a Karst Site using Electrical Resistivity Tomography and Seismic Full Waveform Inversion

Karst geology is characterized by the presence of sinkholes and voids, which may pose significant risk to existing infrastructure. Sinkhole formation is often observed near active quarries, where dewatering operations can alter regional groundwater flow patterns leading to subsidence and increased void formation. In these areas, identifying locations which may be susceptible to sinkhole formation requires an ability to map dissolution features within the rock. Traditional geotechnical explorations alone are not well-suited to this effort as they only provide subsurface information at discrete points and therefore may miss voids within the rock. Geophysical methods offer a means to produce continuous profiles of the rock surface and possible locations for voids but interpreting the results of these tests in karstic geology can be challenging. This study uses 2D electrical resistivity and seismic surveys at a site with previous sinkhole activity along an interstate in central Alabama. The site is adjacent to a limestone quarry. Resistivity data is collected using 2D dipole-dipole and strong-gradient arrays. The seismic data is processed using a full waveform inversion (FWI) technique. Subsurface profiles interpreted from the geophysical surveys are then compared to borehole data from previous site investigations. Results from the geophysical surveys are found to be consistent with borehole data regarding variation of bedrock depth and identification of possible sinkhole features. Potential limitations and sources of error pertaining to each survey type are considered.

Integration of electrical resistivity and soil analysis for Agricultural soil characterization—a case study

Integration of 2D electrical resistivity method and soil analysis was used to characterize the topsoil in the farmland of Federal University Oye-Ekiti, Nigeria, to determine its suitability for agricultural purposes. A 2D electrical resistivity survey was carried out along four traverses using Wenner array electrode configuration with electrode spacing ranging from 1 to 5 m and station interval of 1 m. The acquired 2D electrical resistivity data were processed and inverted using DIPRO version 4.01 software. Forty (40) soil samples were collected along the established traverses at depth intervals of 0.5 and 1.0 m to estimate the moisture contents and grain size distributions. The 2D inverted resistivity sections revealed three probable geologic materials namely clay, clayey sand, and sand. Grain size analysis showed that the farmland is made up of gravel, sand, and fines (silts and clay) with mean percentage distributions of 8.77%, 80.08%, and 11.15% respectively. The moisture content of the forty (40) soil samples analyzed ranges from 10.2 to 18.6%, with an average value of 11.91%. Areas of low electrical resistivity values were observed to coincide with zones of fine particles and high moisture content and are identified to be favorable for crops in the farmland. This study shows the effectiveness of the electrical resistivity method and soil analysis in determining the variability of soil moisture content at shallow depth and in selecting soil that can aid the optimum production of crops.

Assessment of groundwater potential zone using GIS-based multi-influencing factor (MIF), multi-criteria decision analysis (MCDA) and electrical resistivity survey techniques in Raipur city, Chhattisgarh, India

Abstract The present study involved the combined applications of advanced techniques and tools like remote sensing, geographic informatic system (GIS), electrical resistivity, MCDA, to assess the potential zones of groundwater occurrence. Several prepared thematic layers, including geology, geomorphology, rainfall, lineament, land use land cover (LULC), drainage density, soil type, slope, and soil texture, were assigned with a weight, depending on their influence on groundwater potential. Normalization concerned with relative contribution is applied in this study using the AHP method. Vertical electrical sounding has been conducted on different points to locate water-bearing formations/fracture zones. The resulting groundwater potential areas that are delineated applying these methods have been categorized into five zones, low, medium, medium-high, high, and very high potential. The groundwater potential zones demarcated show that high potential zones are present in the west and north-eastern portion, while low to medium groundwater potential is located in the central and eastern portion. The obtained result was validated using well yield data, and ROC method from which result accuracy obtained is 80% and the area under the ROC curve is found to be 0.857 at a significance value of less than 0.001, which justifies the efficacy of the proposed approach in the demarcation of groundwater potential zone.