Integration of Electrical Resistivity Tomography and Seismic Refraction Tomography to Investigate Subsiding Sinkholes in Karst Areas

Abstract

Operational and safety issues associated with subsiding sinkholes in karst areas start with the definition of fractures and joints, causing ground weakness. Conventional geotechnical boreholes and geological mapping must be complemented with indirect subsurface exploration techniques to detail those structures. This work aims to use electrical resistivity tomography (ERT) and seismic refraction tomography (SRT) near-surface geophysical techniques to infer the 2D and 3D geometry of sediment-infilled sinkholes formed by the conjunction of fractures and joints in karst areas. Geophysical surveys were performed in a sediment-infilled sinkhole area with two sectors of different subsiding and infilling degrees formed by the conjunction of two fault systems in an experimental research area in the Sierra de Gádor Mountains in southeastern Spain. The ERT survey delimited the geometry of the sinkhole area, including the main fault-boun4ded limits, other minor faults, buried epikarst forms, and the distribution of coarse and clay-rich infilling. The SRT survey corroborated the structure and disambiguated clay-rich and high-moisture-content structures giving similar velocity fields. The integration of the ERT and SRT techniques provides indirect 2D and 3D visualizations of the ground of interest in predicting weakness-triggering mechanisms associated with the regional karst structure. This trial in an experimental uninhabited area, with the possibility of exploring subsiding karst structures is of special interest for designing operational and safety measures in urban areas, where similar karst structures may go undetected and monitoring capability is often more limited. The technological development of the used techniques enables the periodical geophysical monitoring of karst structures, thus making the identification of structural changes modifying the land safety and hydrological mechanisms feasible over time.

Application of Electrical Resistivity Tomography in Geotechnical and Geoenvironmental Engineering Aspect

“…It is a nondestructive test, and the purpose of electrical surveys is to determine the subsurface resistivity distribution by making measurements on the ground surface and also characterize subsurface properties, i.e., structure, water content, or fluid composition [2]. This method is widely used in hydrogeological, environmental, and geotechnical research as it can potentially reveal the subsurface image [3][4][5][6][7][8][9][10]. This technique is used for the investigation of morphotectonic [11], weathering studies [12], landform evolution in mountain areas [13], permafrost detection [14], and exploration of underground karst structures [15].…”

“…That is why the ERT technique is now often used in landfills to inspect the moisture variation in the landfilled waste and the rate of waste degradation to have controlled leachate generation [25]. Apart from this, ERT technology is now vastly being used in geotechnical investigation [4][5][6][7][8][9][10]21,26]. To determine the unknown foundation depth, slope failure investigation, crack detection, the existence of sinkholes, foundation failure, moisture variation in pavement base materials, soil movement, etc., are broadly examined by the ERT method.…”

Application of Seismic Refraction Tomography in Determining the Soil Hardness Level in IKN Nusantara Area

“…Seismic Refraction Tomography (SRT) has become a common method for exploring the geotechnical properties of soil (Asamoah et al, 2018;Whiteley et al, 2018;Oladotun et al, 2019;Adewoyin et al, 2021;Shin et al, 2022;Opemipo et al, 2022;El Hameedy et al, 2023). According to Jabrane et al (2023) and Abudeif et al (2023), this technique relies on the principle of seismic wave retardation, which is dispersed by layers of rocks beneath the surface. This dispersion produces a representation of the variation in compressional wave velocity (P-wave velocity -Vp) within the earth.…”

Integrated geophysical methods for studying the karst system of Ravansar

“…ERT has proven to be highly effective in these applications (Ismail & Anderson, 2012). Cavities, which can contain water, loose sediments, or air, exhibit distinct resistivity values that differ from their surroundings (Jabrane et al, 2023;Martínez-Moreno et al, 2014;Vargemezis et al, 2007). However, in certain cases, the precise delineation of cavities can be challenging due to exceptionally high resistivity conditions or the presence of a mineralconductive layer surrounding the cavity (Martínez-Moreno et al, 2014;Putiška et al, 2012).…”