INTEGRATED METHODS USING MULTICHANNEL ANALYSIS OF SURFACE WAVES (MASW) AND ELECTRICAL RESISTIVITY TOMOGRAPHY (ERT) FOR GEOTECHNICAL HAZARD ASSESSMENT (A Case Study of Queen Ede, Benin City, Edo State)

Identification of Areas at Risk of Abrasion Application of Electrical Resistivity Tomography (ERT) Method on Nangai Beach, North Bengkulu

A study of the underground structures in areas prone to abrasion of Nangai Beach, North Bengkulu Regency. In this study, 2D images of the subsurface structure at the Nangai Beach site were obtained using the Wenner-Schlumberger configuration, while 3D representations were obtained using the Electrical Resistivity Technique (ERT). To protect coastal materials, the main objective of this research is to identify rock types that are resistant to seawater erosion and measure the resistivity of rocks that can be eroded. In addition, software (ERT LAB 64, View Lab 3D and Res2Dinv) was used to analyze the data by processing it and displaying animage of the resistivity value. The interpretation results show that the coastal zone of the study area is dominated by clays with resistivity (> 34 m). The shoreline of Nangai beach consists of shale clay (>> 437 m). Rocks having a resistivity value (437 m) are not easily eroded by erosion in shale clay. This is because the rocks known as shale clay have low porosity, resulting in compact rock density. Restoring damaged soil and planting trees near the coast are two ways to slow down the abrasion process.

Application of 2-D Electrical Resistivity Tomography and Radiometric Techniques in Assessing Groundwater Vulnerability and Soil Contamination in Jos Mining Area, Nigeria

Groundwater resources within mining environments are increasingly threatened by contaminant infiltration and radionuclide migration resulting from intensive mineral exploitation. This study integrates Vertical Electrical Sounding (VES), Two-Dimensional Electrical Resistivity Tomography (ERT), and radiometric techniques to assess groundwater vulnerability and soil contamination in the Rayfield mining area of Jos Plateau, North-Central Nigeria. Geoelectrical investigations were conducted to delineate subsurface lithology, identify aquifer units, and evaluate groundwater vulnerability, while radiometric analyses were performed to determine the distribution and potential hazards of naturally occurring radionuclides. The VES results revealed a seven-layer geoelectric succession characterized by an HQ-type curve, with resistivity values ranging from 20.5 to 509 Ωm. A thick fractured basement aquifer with a resistivity of 271 Ωm and thickness of approximately 36.2 m constitutes the principal groundwater reservoir. ERT imaging delineated three distinct subsurface zones comprising a conductive contaminated zone, saturated weathered materials, and consolidated lateritic-basement formations. A prominent low-resistivity anomaly (<36.5 Ωm) was interpreted as a contaminant plume associated with mining-derived leachates and radionuclide-enriched pore fluids, indicating active contaminant migration through weathered and fractured pathways. Radiometric assessment showed mean values of 88.91 Bq kg⁻¹, 279.4 μSv y⁻¹, 0.24, 0.33, and 0.17 × 10⁻³ for Raeq, AGED, Hex, Hin, and ELCR, respectively, all below internationally recommended limits. However, localized radionuclide enrichment was observed at specific lithological horizons. The integrated interpretation indicates moderate to high groundwater vulnerability despite favourable groundwater potential. The study demonstrates that combining geoelectrical and radiometric methods provides an effective framework for identifying contaminant migration pathways, evaluating environmental risks,...

Groundwater Identification Using the Geoelectric Method (Electrical Resistivity Tomography/ERT) For the Utilization of Mining Areas

Assessment of hydrogeophysical delineation of groundwater zones using vertical electrical sounding (VES) in Jeypore Block, Koraput District, Odisha

Groundwater occurrence in hard-rock terrains is complex and spatially heterogeneous, controlled by weathered and fractured zones with limited surface expression. This research integrates Vertical Electrical Sounding (VES) with remote sensing, GIS and Analytical Hierarchy Process (AHP) for groundwater potential mapping of Jeypore Block, Koraput District, Odisha. This area is underlain by Eastern Ghats Mobile Belt rocks such as khondalites, charnockites, and granite gneisses. Fifteen VES surveys using Schlumberger configuration were conducted across the study area, with electrode spreads up to 800 m. Resistivity data were interpreted using IPI2WIN software, producing one-dimensional resistivity models and Dar-Zarrouk parameters. Subsurface profiling revealed distinct lithological layers consisting of topsoil, laterite, sandstone, weathered/fractured granite, and compact bedrock. Layer thicknesses ranged from 0.6 to 20.4 m in the first layer to 99.5 m in the third layer. Iso-resistivity maps generated using Surfer-25 showed significant lateral heterogeneity. Low-resistivity zones (2.6–105.2 Ωm) indicated saturated formations, whereas high-resistivity values (> 150 Ωm) represented compact basement rocks. Curve-type analysis identified predominantly AAA-type curves, which indicate increasing resistivity with depth. HA-type curves observed at two locations suggested the presence of conductive, water-saturated layers favourable for aquifer development. VES-derived parameters were integrated with twelve geospatial thematic layers, including geology, geomorphology, soil, NDVI, lineament density, drainage density, rainfall, slope, physiography, land use, groundwater fluctuation, and hydrogeology, using the AHP framework. The consistency ratio of the model was 2.36%, indicating reliable thematic weighting. Validation via pumping tests and ROC analysis (AUC = 0.86) confirmed model reliability. This approach offers a scientifically robust framework for sustainable groundwater management in structurally complex hard-rock terrains.

Integrated Electrical Resistivity Tomography and SPAC Microtremor for Local Site Response Assessment toward Sustainable Disaster Risk Reduction: A Case Study of Setiling Village, Central Lombok

Local geological conditions strongly influence seismic-wave propagation and earthquake ground response, particularly in heterogeneous volcanic environments. This study aimed to characterize shallow subsurface conditions and assess local seismic site response in Setiling Village, Central Lombok, Indonesia, by integrating two-dimensional Electrical Resistivity Tomography (ERT) using the Wenner–Schlumberger configuration with Spatial Autocorrelation (SPAC)-based microtremor analysis. Three ERT profiles and twenty SPAC measurement points were acquired to evaluate subsurface heterogeneity and near-surface stiffness. The ERT results revealed significant resistivity variations associated with volcanic lithology, weathering intensity, moisture content, and groundwater conditions. Conductive zones (<100 Ωm) were interpreted as highly weathered volcanic deposits, whereas higher resistivity zones (>600 Ωm) represented relatively competent volcanic materials. SPAC-derived Vs30 values ranged from 150 to 525 m/s, corresponding to NEHRP Site Classes C, D, and E. Integrated interpretation demonstrated a consistent relationship between resistivity and Vs30, indicating that progressive volcanic weathering simultaneously reduces electrical resistivity and subsurface stiffness. The integrated ERT–SPAC approach provides a reliable framework for village-scale seismic site characterization, supporting seismic hazard assessment, risk-informed spatial planning, resilient infrastructure development, and disaster risk reduction in tropical volcanic regions.

Shear Wave Velocity Profiling & Rock Mass Characterization at Pavagadh Hill Using the Multichannel Analysis of Surface Waves (MASW)

Multichannel Analysis of Surface Waves (MASW) is a geophysical method used for subsurface characterization by measuring the variation of shear-wave velocity (Vs) with depth and evaluating the stiffness properties of near-surface materials. The prime focus of this study is MASW testing was carried out at multiple locations situated at different elevations of Pavagadh Hill to characterize subsurface rock mass conditions and to understand the variation of engineering parameters along the hill slope. Conventional borehole-based seismic testing methods such as cross-hole and downhole testing are expensive, intrusive and spatially limited in heterogeneous geological conditions. Surface wave based geophysical techniques have therefore emerged as efficient and non-destructive alternatives for continuous subsurface characterization. Among these techniques, the Multichannel Analysis of Surface Waves (MASW) method has become one of the most accepted approaches for estimating shear-wave velocity profiles using the dispersive characteristics of Rayleigh waves propagating through layered media. The obtained Vs profiles were used to evaluate variation in subsurface stiffness and rock mass conditions with depth at different elevations. Further, Vs₃₀ values were calculated for selected locations and the sites were classified according to NEHRP site classification criteria. Based on the estimated shear wave velocity important engineering parameters such as shear modulus (G), rock mass deformation modulus (Em), Geological Strength Index (GSI), Uniaxial Compressive Strength (UCS) and bearing capacity were evaluated. The results obtained from this study provide valuable input for safe foundation design, slope stability assessment and infrastructure development at Pavagadh Hill.