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Rock salt is considered a suitable medium for the permanent disposal of heat-generating radioactive waste due to its isolation properties. However, excavation damage and heating induce complex and heterogeneous thermal-hydrological-mechanical (THM) processes across different zones. Quantifying this heterogeneity is crucial for accurate long-term performance assessment models, but traditional methods lack the necessary resolution. This study employs 4D electrical resistivity tomography (ERT) monitoring during controlled heating experiments in a salt formation to unravel the spatiotemporal dynamics of THM processes. Advanced time-lapse inversion and clustering analysis quantify subsurface properties and map the heterogeneity of THM dynamics. The ERT results can estimate subsurface properties and delineate the damaged and intact zones, enabling appropriate parameterization and representation of processes for long-term modeling. This approach may be used in further improving the predictive models and ensuring the safe long-term disposal of radioactive waste in rock salt.

The fault fracture zone is closely related to groundwater activity, which is a common target for water exploration and well drilling. It is often located below the cover layer, which is difficult to identify solely through geological surveys due to its concealment. Geophysical methods are a common and effective means of quickly identifying fault fracture zones. The fault fracture zones and the developed fissures within them often manifest as low-resistivity anomalies. When under low-resistivity background conditions, the identification difficulty of the fault fracture zone increases. A single geophysical method often has ambiguity and uncertainty in identifying fault fracture zones. Therefore, this paper uses integrated geophysical methods to determine the location, depth, and properties of a fault fracture zone and further assess it based on geological data, achieving good results. First, electrical resistivity tomography is used to determine the approximate location and range of the fault fracture zone. The abnormal feature is a low-resistivity strip with a localized low-resistivity trap. The low-resistivity trap area is a concentrated zone of fault fracture with fractured lithology. The audio-frequency magnetotelluric method is used to determine the depth of the bottom boundary of the fault fracture zone The anomalous feature presents a wide and gentle U-shaped low resistivity. The drilling depth is determined by inferring the depth of the bottom boundary of the fault fracture zone using the audio-frequency magnetotelluric method. The composite profiling method is used to accurately locate the fault fracture zone and determine the drilling position. The anomalous feature is determined to be a synchronous low-resistivity anomaly, which changes from a V-shaped to a U-shaped from shallow to deep. As the electrode distance increases, the inferred width of the fault fracture zones change from narrow to wide. To reduce the ambiguity and uncertainty in identifying fault fracture zones in low-resistivity environments using conventional electrical and electromagnetic methods, the microtremor horizontal-to-vertical spectral ratio (HVSR) method is used to further review the location of the fault fracture and fissure zones. The abnormal feature is a horizontal-to-vertical (H/V) high-value trap. The apparent resistivity sounding curve is used to determine the burial depth of water-bearing fissure zones in the fault fracture zone. The anomalous feature is a V-shaped low-resistivity anomaly. Then, the water content of the hanging and foot walls of the fault based on hydrogeological conditions is analyzed. Finally, on the basis of the construction site conditions, a drilled hole is performed near the fault fracture zone (342.5 measuring points), with a depth of 160.3 m. When the water level drawdown is 6.90 m, the water inflow is 107.40 m3/day. After drilling verification, the selection and application process of the above method is a scientifically reasonable water exploration model that can be applied to the same geological background conditions. The case study results show that the combination of geophysical prospecting methods, namely, electrical resistivity tomography, audio-frequency magnetotelluric method, composite profiling method, microtremor HVSR method and apparent resistivity sounding curve can effectively explore the fault fracture zones under low-resistivity background conditions. [ABSTRACT FROM AUTHOR]

Salt marshes are ecologically and economically valuable ecosystems, yet are vulnerable to marsh dieback, the rapid death of marsh vegetation, which has affected coastal areas along the southeastern and Gulf coasts of the United States in recent decades. This study used multichannel electrical resistivity tomography (ERT) surveys to investigate the shallow hydrostratigraphy (up to 39.2 m depth) of three dieback-affected salt marshes along the Georgia coast to evaluate the influence of site location, vegetation status (dieback versus healthy), and tidal conditions on ERT profiles. ERT profiles revealed consistent subsurface resistivity patterns across the marsh platforms, with low resistivity (0.2 ohm-m) at shallow depths indicating saltwater saturation and a transition to higher resistivity (up to 8.1 ohm-m) at greater depths, potentially signifying a shift to brackish conditions and/or sandy strata. The ERT data indicated that the hydrostratigraphy is similar across all study sites. Furthermore, the ERT data remained consistent regardless of vegetation status, tidal variations, and seasonal changes, suggesting that the processes driving the recovery of marsh dieback are independent of the shallow marsh stratigraphy. These findings enhance our understanding of marsh subsurface conditions, supporting efforts to better understand marsh resilience and guide future research on salt marshes. [ABSTRACT FROM AUTHOR]

Seepage accelerates the weathering and destruction of cultural heritage sites, posing a major preservation challenge, while the concealed nature of seepage channels complicates their detection due to noninvasive requirements. In this study, we applied a comprehensive geophysical approach, integrating electrical resistivity tomography (ERT) and self-potential (SP) techniques, to image seepage channels within the Leitai heritage site. These potential seepage channels have already caused a collapse pit measuring 3.1 m × 2.7 m on the site's surface. We began with 2D ERT surveys, which were then combined for 3D inversion to reveal the resistivity structure of the site. Subsequently, SP data were extracted along typical survey lines using interpolation algorithms, and these were inverted to supplement and verify the resistivity structure. The results from both techniques were highly consistent, indicating the presence of internal channels within the site. This comprehensive geophysical approach provides critical insights and references for the subsequent restoration efforts of the Leitai heritage site, ensuring the protection and preservation of this culturally significant landmark. Moreover, the method proposed in this study can be easily applied to the preservation of similar cultural heritage sites elsewhere. [ABSTRACT FROM AUTHOR]

Among the common arrays of electrical resistivity tomography, the pole-dipole array is widely used due to its unique advantages such as more apparent resistivity information in the measured profile and the ability to realize advanced detection. However, this array requires an infinite pole, and there is still no uniform standard on the least amount of distance from the survey line that can be regarded as infinity, which is crucial in some space-limited measurement environments. Therefore, in this study, the geometric factor K of the pole-dipole array and quadrupole array is analyzed first, and the root mean square error rate (RMSE%) between different geometric factors is calculated. Then the threshold is set to 5% to determine the theoretical infinite pole minimum multiple [ m ] t = 2 . With the premise that the survey line length is L and the distance between the infinite pole and the starting electrode of the survey line is m*L, when the survey line length multiple is m ≥ [ m ] t = 2 , the influence of the infinite pole on the measured data can be ignored in engineering. Finally, verification experiments are carried out in different environments with anomalous bodies of different properties as test objects, and it is proved that the theoretical value [ m ] t = 2 is applicable to various modes of pole-dipole array and tested objects with different properties. [ABSTRACT FROM AUTHOR]

Infrastructure development into peat necessitates geotechnical engineers to find a better profiling method. The conventional profiling carried out by either a localized peat augering or a borehole drilling is often subjective, lacking of details, time consuming and high cost. This paper presents results and analysis of in-situ tests that combines Electrical Resistivity Tomography (ERT) and Multichannel Analysis of Surface Wave (MASW) methods. The results show that ERT method is a good tool for delineating the boundary between peat and underlying mineral soil using their large contrast in electrical resistivity values. The ERT enables the peat thickness to be determined accurately, but lacks of information regarding peat mechanical properties. On the other hand, the MASW provides a lower contrast between the peat and the mineral soil layers compared to the ERT, but it can provide the mechanical properties of the two layers based on shear wave velocity measurements. Hence, the combination of these two methods were found to be improving the peat profiling for engineering application. The results correlate well with the existing peat auger and borehole records in the study area. The combined ERT and MASW methods is recommended to be practically used by engineers as the current best solution for peat profiling. [ABSTRACT FROM AUTHOR]

Electrical Resistivity Tomography (ERT) can be a key tool for aiding in characterization of karst geohazard risks at proposed landfill sites. This study is proximal to the south-central Kentucky karst and Mammoth Cave National Park and possesses siliciclastic cap rock upland areas that pose relatively high groundwater-contamination risks due to adjacent ravines floored by carbonates. Complex stratigraphy associated with the Mississippian-Pennsylvanian unconformity and juxtaposition of heterolithic sedimentary rocks in general presents further challenges for demarcating hydrogeological characterization of the base of engineered landfills. A conceptual site model integrates ERT surveying and field geology that both satisfactorily characterize the site and risks to groundwater resources without conducting multiple borings. The proposed landfill site is compared to well-known and mapped caves at a landfill near Bowling Green, Crumps Cave near Smiths Grove, and River Styx Spring at Mammoth Cave. Our work entails review of ERT datasets at known cave sites and compares these to two ERT profiles that traversed the proposed landfill site, which are integrated with study of outcrops, and an excavated pit and trench. ERT data range from several low 10 s to about 400 Ω-meter values for mud rock units whereas sandy units possess ERT values from approximately 500 to several tens of thousands of Ω meters. The greatest values are indicative of basal Pennsylvanian Caseyville Sandstone, and these exceed 32,000Ω meters. In comparison, ERT values at known cave sites range from one to 100,000 Ω meters, with elevated, dry rock or possibly dry (air filled) caves interpreted from the greatest values and low values reflective of conductive underground cave streams and moist caves. An unexpected challenge specific to the Hart County landfill study includes occurrence of well-drained and highly weathered Caseyville at the highest elevations of the site causing increased electrical contact resistance during ERT surveying. The overall ERT contrast however, between quartz-rich and clay poor strata (high-resistivity rocks and regolith) and clay-rich strata (low-resistivity rocks) provides independent data consistent with the observed stratigraphy exposed in site exposures. Nonuniqueness of conductive intervals at the Hart County site contrasts with other conductive areas at depth associated with moist or wet cave passages as documented at Crumps Cave and Mammoth Cave. [ABSTRACT FROM AUTHOR]

Karst sinkholes pose a great danger to people and infrastructure in many countries, so effective methods for assessing karst hazard are needed. However, there are currently no modern regulatory documents and methods for assessing the danger of karst sinkholes. The article describes the methods and provides examples of the application of several methods for assessing karst hazard, tested in real conditions in the karst zone of the Bryansk region [ABSTRACT FROM AUTHOR]

Talcher Coalfield is one of the most important coalfields considering thermal grade coal reserves in India; nevertheless, hardly any published geophysical study is available for mapping the subsurface coal, in-crop zone, fault location, formation boundary, etc. In the present study, a combined analysis of electrical resistivity tomography (ERT) in five profiles and high-resolution shallow seismic (HRSS) survey in two profiles was carried out in Goribandh at the northern–eastern part of the Talcher Coalfield, Odisha, India, to study the structural control of coal seams and to delineate the coal potential zone and non-coal zone. Geological core data from three boreholes were utilized to validate the ERT and HRSS results. Three ERT profiles (ERT_P1, ERT_P2, and ERT_P3) data were acquired in perpendicular to the strike direction, and two ERT profiles (ERT_P4 and ERT_P5) data were collected in the strike direction. The purpose of the acquisition of ERT data in the strike direction is to correlate the resistivity values at the cross point of dip lines and strike lines. Two HRSS profiles (HRSS_P1 and HRSS_P2) data were collected along the same two corresponding dip lines of the ERT profiles (ERT_P1 and ERT_P2). The ERT data were collected using Wenner–Schlumberger array at 10 m electrode spacing with multiple roll-along sequences to cover the desired profile length with an approximate profile line spacing of 200 m. The Res2Dinv program was used to execute the inversion of the combined data set. The HRSS data were acquired by 'End-on-Shooting' method using 24-fold common depth point survey at 4 m geophone spacing with multiple roll-along sequences to cover the desired profile length with approximate profile line spacing of 200 m, where near trace and far offsets trace were 88 and 276 m, respectively. HRSS data were analyzed using Paradigm 19 seismic processing software. Comprehensive analysis of five numbers of 2D ERT sections (ERT_P1-ERT_P5) and two numbers of HRSS sections (HRSS_P1 and HRSS_P2) indicates that the southern part of the study area is characterized by relatively low to moderate high resistivity (100–500 Ωm) distribution while seismic sections demonstrate multiple strong reflecting horizons, due to carbonaceous beds as identified in the boreholes, indicating Barakar formation. The northern part is characterized by high resistivity (200–1000 Ωm) distribution, while seismic sections exhibit multiple distributed minor reflectors due to boulder beds and or compact sandstone. The combined study of ERT and HRSS data delineates a prominent fault zone F4, indicating a contact boundary between the Talchir and Barakar formations. [ABSTRACT FROM AUTHOR]

The joint inversion of radio magnetotelluric and electrical resistivity tomography data has the potential to reduce the uncertainties in the subsurface conductivity model. This is particularly beneficial when the data sets offer complementary information about the subsurface. However, the traditional gradient-based inversion methods pose challenges in quantifying uncertainty, as they yield a single model with limited appraisal of parameter uncertainty. The Bayesian inversion approach stands out for its capacity to provide quantitative assessments of uncertainty in the inverted model parameters. This is accomplished by generating an ensemble of models, leading to a posterior distribution that encapsulates both prior information concerning model parameters and the data set information. We have implemented a transdimensional Markov chain Monte Carlo algorithm to perform the joint inversion of radio magnetotelluric and electrical resistivity tomography data. Through synthetic data studies, we illustrate how the inclusion of two complementary data sets can effectively reduce uncertainties in model parameters and how the model parameter uncertainties can be quantified. Subsequently, the developed algorithm is tested using exemplary field data from a waste site near Roorkee, India. Intensive prior geoelectric and transient electromagnetic as well as radio magnetotelluric studies investigated possible waste water seepage with a potential to contaminate the shallow aquifers. The derived subsurface structure from our transdimensional Bayesian results compare well with the deterministic results for the exemplary profile, but in addition provide comprehensive uncertainty estimates. [ABSTRACT FROM AUTHOR]

Electrical resistivity tomography inversion often encounters uncertainty stemming from two primary sources: epistemic uncertainty, arising from imperfect underlying physics and improper initial approximation of model parameters, and aleatory variability in observations due to measurement errors. Despite the widespread application of electrical resistivity tomography in imaging, the resistivity distribution of subsurface structures for various hydro-geophysical and engineering purposes, the assessment of uncertainty is seldom addressed within the inverted resistivity tomograms. To explore the combined impact of epistemic and aleatory uncertainty on resistivity models, we initially perturb the observed data using non-parametric block-wise bootstrap resampling with an optimal choice of the block size, generating different realizations of the field data. Subsequently, a geostatistical method is applied to stochastically generate a set of initial models for each bootstrapped data set from the previous step. Finally, we employ a globally convergent homotopic continuation method on each bootstrapped data set and initial model realization to explore the posterior resistivity models. Uncertainty information about the inversion results is provided through posterior statistical analysis. Our algorithm's simplicity enables easy integration with existing gradient-based inversion methods, requiring only minor modifications. We demonstrate the versatility of our approach through its application to various synthetic and real electrical resistivity tomography experiments. The results reveal that this approach for quantifying uncertainty is straightforward to implement and computationally efficient. [ABSTRACT FROM AUTHOR]

Although relatively far (over 100 km) from the epicenter of the 17 August 1999 İzmit earthquake, the Istanbul/Avcılar region suffered unexpected severe damage to many buildings and some casualties. Since future earthquakes in this highly populated region are expected in the following decades, it is crucial to assess the seismic risk to develop mitigation strategies. Critical faults in the sea of the study area were mentioned in previous studies, and their possible connections were mentioned, but a dataset showing their connections was not presented. To investigate this aspect further, we performed a geo-electrical survey around Küçükçekmece Lake, which included 14 inverted vertical electrical soundings (VESs) to provide resistivity vs depth sections. We also collected three 2D electrical resistivity tomography (ERT) data profiles. The ERT and inverted VES data show that a network of faults cut the most recent sedimentary units, causing sharp resistivity changes. In this study, land faults for the city of Istanbul were shown for the first time through geophysical studies. Because this area lies off the principal displacement zone of the North Anatolian Fault in this region, such features could represent the reactivation of old tectonic structures. However, we stress that the peculiar geological setting of the Istanbul/Avcılar region should be considered when evaluating seismic scenarios given that a future earthquake will affect the Istanbul metropolitan area. [ABSTRACT FROM AUTHOR]

The present study adopts an integrated approach, combining geophysical and geotechnical techniques for subsurface exploration of a karst limestone site affected for future development of an industrial project. The results from electrical resistivity tomography (ERT) have revealed numerous anomalies suggesting structural discontinuities in the ground at the project site. This discovery has prompted a strategic reassessment, leading to the incorporation of direct methods, particularly core drilling, and deferred loging to validate and further enhance the insights obtained from ERT. Through correlation of the acquired data, the results unveil relatively uniform lithological formations, punctuated by localized anomalies associated with cavities/paleokarsts filled by collapsed materials within deep limestone layers. Additionally, drilling log results emphasize the existence of narrow dissolution zones within the depth range of 60 to 70 m. These structures have the potential to develop into cavities over time. The integration of geophysical and geological data acts as a guide for subsequent geotechnical analyses, enabling informed decision-making for the project's design and foundation to ensure long-term stability. Ultimately, this information has unveiled the complexities of the site, providing an enhanced understanding of underground geological conditions. This knowledge serves as a robust assurance tool for developers, underscoring the essential role of geo engineering in delineating terrain conditions and mitigating potential hazards. [ABSTRACT FROM AUTHOR]

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Observing the subsurface architecture of the deep Critical Zone (CZ), which lies beyond the uppermost layer of accessible soil, is a complex but crucial task. Near‐surface geophysics offers an alternative to accessing the deep CZ at scales relevant to fluid, nutrient and gas transport. As geophysical instruments are sensitive to different subsurface physical properties, their combination can enhance insight into CZ architecture. However, the agreement between and complementarity of multiple geophysical techniques has not been widely assessed for CZ‐related questions. This study employed geophysics to image a highly weathered lateritic hill rich in iron oxides developed from Archean granite within the Avon River Critical Zone Observatory, Western Australia. Data gathered from an electrical resistivity tomography (ERT) and horizontal‐to‐vertical‐spectral‐ratio (HVSR) passive seismic transect were used to visualise CZ architecture through specific resistivity values and ambient noise contrasts. Both techniques revealed a notable degree of lateral variability consistent with the formation of the ~3–4 m thick duricrust‐capped hilltop, the creation of gullies in the sodic material of the pallid zone exposed along the slope and the deposition of ~11 m thick colluvial sediment at the foot slope. Calculated bedrock depth was consistent between the HVSR and ERT instruments along the hilltop plateau but varied from ~23 m to 31 m on the slope and 32 m to 39 m at the foot slope, respectively. Overall, the vertical variation depicted by the ERT, including the differentiation of two layers within the lateritic weathering profile ‐ the pallid zone and saprolite – made up for the inaccuracy of the HVSR technique in depicting layers of similar composition. Moreover, the HVSR method clearly depicted bedrock depth, overcoming the partial masking of the bedrock by saline groundwater in the ERT model. The complementarity of these two methods allowed the development of a detailed conceptual model of subsurface CZ architecture within a saline lateritic weathering profile. [ABSTRACT FROM AUTHOR]

This study presents case studies conducted in northeast Thailand, where sinkhole collapses have continuously occurred in certain areas. Rapid descent of groundwater in a karst aquifer has the potential to induce sinkhole collapses within the karst morphology. Field investigations have revealed surface expressions of potentially hazardous sinkholes associated with zones of groundwater depression and abandoned groundwater wells. 2D electrical resistivity tomography (ERT) profiles were executed along the trend of such sinkhole collapses. The ERT results were combined to outline potentially dangerous cavities and continuous fractures. Sinkhole collapses in this scenario are primarily induced by groundwater depression and rainfall. Groundwater flows through conduits connecting a quarry with a karst cavern network, and dewatering of the quarry reduces the surrounding groundwater level. Runoff from rainfall percolates within overburden and enters air‐filled cavities. Additionally, quarry blasting activities may cause vibrations that trigger the formation of sinkholes. Observations of surficial collapse features were generally consistent with geophysical ERT‐interpreted subsurface cavities and fractures. Consequently, implementing regulatory measures to restrict the depth of limestone quarrying that affects groundwater levels may be necessary to prevent sinkhole collapses. The sinkhole formation phenomenon underscores a critical link between groundwater fluctuations and the stability of karst landscapes. [ABSTRACT FROM AUTHOR]

Thailand’s fossil forests hold international importance for a variety of reasons. The operation of a gravel mine exposed sediment layers containing petrified wood logs, highlighting the critical need to preserve these unique artifacts and address associated environmental concerns. A comprehensive lithological study was conducted on pit walls. Employing 2D ERT and 2D IP methods, geology was classified from the ground surface and validated through drilling logs. The sediment and deposit categorization at gravel pit sites revealed four distinct units: Unit I, conglomeratic sand, exhibiting characteristics typical of fluvial deposits; Unit II, indicating alluvial fan deposition with lenticular gravel and sand highlighting the presence of petrified wood logs; Unit III, massive gravel suggesting channel deposits of an alluvial fan with an abundance of petrified wood; and Unit IV, red soil (collapsible soil). The 2D ERT method successfully examined the boundary sediment layer and mudstone, though classification of sediment units was not achieved. Quaternary terrace sediments underlie the mudstone, identified as an aquitard that effectively prevents surface contamination of the groundwater aquifer. The data from this study serves as fundamental geological information, providing remarkable and essential evidence for the preservation of petrified wood and the safeguarding of the groundwater environment. This site is particularly an outstanding geosite. This research contributes to our understanding of depositional environments and geological processes and proposes conservation strategies. [ABSTRACT FROM AUTHOR]

This article discusses the significance of geophysical research in the context of historical renewal, emphasizing its contributions to risk assessment, sustainable redevelopment, and non-uniqueness in geophysical interpretation. The geophysical studies were conducted in the surroundings of the Palace of Rzuchów, timing to locate the modern infrastructure, historical objects, and other environmental elements that can either threaten the renewal process or add value to the historical heritage. We used three geophysical methods to study the palace surroundings: frequency domain electromagnetics, magnetometry, and electrical resistivity tomography. The findings revealed significant anomalies corresponding to buried modern infrastructure and historical artifacts, offering critical insights for preserving cultural heritage while planning sustainable redevelopment, thus demonstrating the practical utility of integrating geophysical methods in complex historical and environmental contexts. [ABSTRACT FROM AUTHOR]

Permafrost landscapes are becoming increasingly susceptible to widespread thaw due to climate change. Collating historical and ongoing data are critical for assessing permafrost conditions and spatiotemporal changes. Electrical resistivity tomography (ERT) is a geophysical technique that has become standard practice for characterizing permafrost. However, resistivity data—particularly raw measurements—often go unpublished and unshared, resulting in missed opportunities for knowledge exchange and collaboration. To fill this gap, we created the Canadian Permafrost Electrical Resistivity Survey database and established clear guidelines for data archival and reuse. Here, we present the first release of the database, which currently houses 280 ERT datasets, including standardized metadata, collected between 2008 and 2022 in British Columbia, Labrador, Northwest Territories, Québec, Yukon, and Alaska. These data present unique opportunities to better understand spatial and temporal variability of permafrost conditions across North America.

Abstract Submarine Groundwater Discharge (SGD) is a major pathway for the discharge of fresh and saline groundwater and associated dissolved compounds into marine environments. However, assessing SGD processes in coastal aquifers is challenging due to inaccessibility, dynamic conditions, complex subsurface geology, and the need for long-term monitoring to capture temporal and spatial variations in SGD rates accurately. This study employs marine continuous resistivity profiling (MCRP) as a main method to assess the presence of freshwater or brackish SGD offshore and to examine its potential seasonal variations. The method has been applied in the coastal alluvial aquifer of Maresme (Spain) and validated with other methods to trace SGD, including salinity profiles, Ra isotopes, and piezometric levels. Several MCRP transects of 700 m long, perpendicular to the coastline, were performed in a coastal marine area to obtain electrical resistivity data of the seabed covering an area of 3 km2. The data was acquired in two field campaigns with contrasting hydrological conditions (dry and wet seasons). The MCRP results allow the identification of areas of fresh SGD in marine sediments, with a clear seasonal variability that indicates a higher discharge of fresh groundwater in the wet season.

The development of fracture zones (broken zones) and underground karst rivers in underlying granite can significantly reduce the recovery rate of ion-adsorption-type rare earth ores. Additionally, leaching solutions flowing along unfavorable geological formations can lead to environmental pollution. Therefore, investigating the development of fracture zones (leakage channels) in granite basements is of great significance. In Changting, Fujian, China, several methods have been used in exploration areas (C1 and C2) to study the characteristics of rare ores. This study has focused on the stratigraphic and structural characteristics of the C2 exploration area. Twelve exploration profiles were designed to collect data using electrical resistivity tomography, and a deep electrical structure model of the study area was obtained through inverse calculations. The results indicated that the exploration profiles effectively delineated the thickness of the weathered granite layer and the spatial distribution characteristics of the deep-seated fault structures, which were consistent with the drilling results within the study area. These findings provide important reference materials for the assessment of ion-adsorption-type rare earth ore reserves, blocking leakage channels, and the layout of recovery tunnels. [ABSTRACT FROM AUTHOR]

In the field of groundwater, accurate delineation of contaminant plumes is critical for designing effective remediation strategies. Typically, this identification poses a challenge as it involves solving an inverse problem with limited concentration data available. To improve the understanding of contaminant behavior within aquifers, hydrogeophysics emerges as a powerful tool by enabling the combination of non-invasive geophysical techniques (i.e., electrical resistivity tomography—ERT) and hydrological variables. This paper investigates the potential of the Ensemble Smoother with Multiple Data Assimilation method to address the inverse problem at hand by simultaneously assimilating observed ERT data and scattered concentration values from monitoring wells. A novelty aspect is the integration of a Convolutional Neural Network (CNN) to replace and expedite the expensive geophysical forward model. The proposed approach is applied to a synthetic case study, simulating a tracer test in an unconfined aquifer. Five scenarios are compared, allowing to explore the effects of combining multiple data sources and their abundance. The outcomes highlight the efficacy of the proposed approach in estimating the spatial distribution of a concentration plume. Notably, the scenario integrating apparent resistivity with concentration values emerges as the most promising, as long as there are enough concentration data. This underlines the importance of adopting a comprehensive approach to tracer plume mapping by leveraging different types of information. Additionally, a comparison was conducted between the inverse procedure solved using the full geophysical forward model and the CNN model, showcasing comparable performance in terms of results, but with a significant acceleration in computational time. [ABSTRACT FROM AUTHOR]

The combination of electrical resistivity and seismic refraction tomography is a common practice for the characterization of subsurface features. Presently, the cross-gradient inversion scheme stands out as one of the most robust joint approaches, and some authors modified it to manage complex topographies on unstructured meshes even if at the expense of introducing additional parameters in the inversion process. We propose in this work a cross-gradient algorithm for jointly inverting electrical and seismic tomographic data on structured meshes in cases with non-flat topography. The proposed approach preserves the benefit of the classical cross-gradient approach without the need to impose physical length scales, as for irregular meshes. The quality of the results is evaluated in comparison with independent inversion through a new standardized cross-gradient index and a fuzzy c -means analysis that provides an assessment of the reconstruction accuracy through the membership function. The proposed method was applied to both synthetic models and field-scale examples located in Central Italy, where an accurate geophysical reconstruction is needed for the rehabilitation of existing dams. For all cases, joint inversion yielded superior results compared to independent inversion, demonstrating better agreement with available borehole data. The effectiveness of the joint approach was also demonstrated by the post-inversion tools, where the new cross-gradient index highlighted changes in structural similarity whilst fuzzy c -means clustering allowed for a quantitative reconstruction (position and shape) of the main units at the sites, facilitating the detection of site layering modifications. [ABSTRACT FROM AUTHOR]

Mobile cranes are essential for transporting heavy materials at construction sites, but their operation carries significant safety risks, particularly due to the potential for overturning accidents. These accidents can be classified into two main categories: mechanical accidents, which are caused by factors such as outrigger failure, excessive load weight, and operator skill, and environmental accidents, which arise from ground subsidence due to groundwater and sinkholes. While numerous studies have addressed the causes and prevention of mechanical accidents, there has been a lack of research focusing on the prevention of environmental accidents. This study presents the development of an Electrical Resistivity Measurement System (ERMS) designed to prevent overturning accidents caused by ground subsidence at mobile crane work sites. The ERMS, mounted on a mobile crane, continuously monitors the ground conditions in real time and predicts the likelihood of ground subsidence to prevent accidents. Unlike typical buried electrode methods, the proposed system features a foldable electrode mechanism and a water supply device, thereby making installation and removal more efficient. Furthermore, it uses a ground stability determination algorithm that qualitatively assesses soft ground conditions, which are the primary cause of ground subsidence. The performance of the ERMS was validated through comparisons with commercial equipment, and its applicability was further confirmed through field tests conducted at mobile crane installations. The ERMS is expected to significantly reduce the risk of accidents caused by ground subsidence during mobile crane operations and to contribute to enhancing overall safety in construction environments. [ABSTRACT FROM AUTHOR]

The Longmen Shan fold and thrust belt, situated on the eastern margin of the Qinghai–Tibet Plateau, is prone to disasters like earthquakes and debris flows. Thus, applying rapid assessment methods for emergency water sources in disaster-affected areas is crucial for local populations and ensuring an effective response to disasters. In this study, we employed electrical resistivity tomography (ERT) to investigate groundwater resources in post-disaster regions. By integrating the results from ERT profiles with geological and borehole information, we determined the lithology and depth of aquifers. Additionally, we analyzed groundwater recharge and discharge patterns relative to surface water during various precipitation periods and generated a hydrogeological profile for the region. Borehole information confirmed our inferred lithology and aquifer depth, thereby ensuring a reliable water supply during emergencies. This study demonstrates the feasibility of ERT for rapidly identifying water resources in geologically complex environments, providing a scientific foundation for water resource management in disaster-prone regions. [ABSTRACT FROM AUTHOR]

The location of covert graves is an important but challenging part of missing persons investigations. Although traditional search techniques, such as foot searches and cadaver dogs, have proved successful, the incorporation of higher technology methods, such as geophysical techniques, can be used to increase the chances of locating covert graves. This article will present a field method for the use of two geophysical techniques, including ground penetrating radar and electrical resistivity tomography, which can successfully locate covert graves in an Australian environment. If the soil and climate conditions permit, this technical protocol can be applied to other clandestine grave search sites as well. Ultimately, by increasing chances of locating the covert grave, and by extension the missing person, a successful judicial outcome can be achieved and highly sought after answers can be provided to the family. [ABSTRACT FROM AUTHOR]

Landslides are one of the primary geological disasters posing significant threats to life and property. Strengthening the monitoring of rainfall-induced landslides is, therefore, crucial. The Direct Resistivity (DC) method can accurately map the subsurface electrical resistivity distribution, making it an essential tool for predicting the position of the slide face. However, when conducting landslide surface DC surveys, various undulating terrains such as ridges and steep slopes often pose accessibility challenges. In such topographies, conventional regular grid measurements become very difficult. Additionally, when the terrain is highly undulating and complex, interpreting apparent resistivity data can lead to erroneous results. In this study, we propose using the DC method to monitor rainfall-induced landslides. By moving away from traditional device setups and utilizing an arbitrary dipole–dipole observation system, we aim to improve efficiency, enhance data resolution, and reduce costs. The resistivity of the slope was found to change significantly during the incubation, formation, and development of a landslide in physical model experiments. Furthermore, the feasibility of our proposed method for assessment rainfall-induced landslides was illustrated by a real case study in South China. [ABSTRACT FROM AUTHOR]

In an irrigated paddy terraced field, subsurface return flow within the plots potentially occurs as long-term ponding water may lead to shallow groundwater uplift to the soil surface. However, subsurface water remains hidden from direct observations. Using an irrigated paddy terraced field located on Ewei Mountain, Taipei, as the study area, we investigated subsurface water during both irrigation and non-irrigation periods by employing electrical resistivity tomography (ERT) and monitoring the groundwater level in wells. The ERT results provided two-dimensional (2D) electrical resistivity sections. The sections show that the subsurface moisture was higher during the irrigation period than during the non-irrigation period. The ERT results indicate the possible location of the shallow groundwater layer and the presence of preferential flows beneath the embankments. Information gathered from rock cores, groundwater level records, and ERT was used to delineate the boundary between the topsoil layer and other geological materials. Rainfall and irrigation can dramatically increase the groundwater table, although it hardly exceeds this boundary. Our findings suggest that considering the subsurface return flow within plots may not be essential in this study area. The investigation with ERT helped assess whether the subsurface return flow needs to be considered in the irrigation management of a terraced paddy field. [ABSTRACT FROM AUTHOR]

This study conducts numerical simulations using the boundary integral equations method to model electric resistivity tomography for investigating an embankment dam. Computational speed is enhanced by formulating the direct problem in integral equations and employing the Fourier transform along the strike direction, thereby reducing the 2.5D problem to a set of 1D integral equations. Synthetic data obtained for potential installations are interpreted using the inversion programme ZondRes2D. The impact of varying dam slope angles and the resistivity of interfacing media on interpretation outcomes is systematically evaluated across different dam models. Main geometric anomalies associated with the three‐dimensional structure of the dam are described. [ABSTRACT FROM AUTHOR]

Locating clandestine graves presents significant challenges to law enforcement agencies, necessitating the testing of grave detection techniques. This experimental study, conducted under Australian field conditions, assesses the effectiveness of time-lapse ground-penetrating radar (GPR) and electrical resistivity tomography (ERT) in detecting pig burials as simulated forensic cases. The research addresses two key questions: (1) observability of graves using GPR and ERT, and (2) changes in geophysical responses with reference to changing climatic conditions. The principal novelty of this research is its Australian focus—this is the first time-lapse GPR and ERT study used to locate clandestine graves in Australia. The results reveal that both GPR and ERT can detect graves; however, ERT demonstrates greater suitability in homogeneous soil and anomalously wet climate conditions, with the detectability affected by grave depth. This project also found that resistivity values are likely influenced by soil moisture and decomposition fluids; however, these parameters were not directly measured in this study. Contrastingly, although GPR successfully achieved 2 m penetration in each survey, the site's undeveloped soil likely resulted in inconsistent detectability. The findings underscore the significance of site-specific factors when employing GPR and/or ERT for grave detection, including soil homogeneity, climate conditions, water percolation, and body decomposition state. These findings offer practical insights into each technique's utility as a search tool for missing persons, aiding law enforcement agencies with homicide cases involving covert graves. [ABSTRACT FROM AUTHOR]

Road pavements undergo various environmental factors such as temperature changes, precipitation, and traffic exposure, which can lead to cracks in asphalt pavements compromising road user safety and necessitating costly repairs. To gain a deeper understanding of the mechanisms behind asphalt pavement cracking, this study proposes the utilization of the electrical resistivity tomography method to measure the electrical resistivity of soil‐supporting road pavements. Electrical resistivity measurements were conducted on soil‐supporting road pavements at various times, both before and during the winter season, in four different road sections. Two of these sections were located on Regional Road N707 in the Ifrane region, while the other two were located on National Road N13 in the Azrou and Timahdite regions. The results of the geophysical campaign provided valuable insights into the impact of the winter season on soil resistance and the formation of cracks in asphalt pavements. To achieve this, electrical tomography was employed to generate 2D images of the electrical resistivity of the soil, which were subsequently compared to asphalt cracking data collected in the field through visual surveys and/or asphalt cores. The 2D analysis of the electrical resistivity images of the road pavements under study revealed a decrease in electrical resistivity values during the winter season. This decrease can be attributed to a combination of factors including asphalt pavement cracking, water infiltration during winter, and soil characteristics supporting the asphalt pavement. These findings offer valuable insights intro targeted maintenance and repair efforts. [ABSTRACT FROM AUTHOR]

ABSTRACT This study presents the results of aerial and geophysical measurements carried out on the Notre‐Dame‐du‐Val chapel in Sotteville‐sur‐Mer (Normandy, France), a former leprosarium dating from the 15th century; the chapel is now deconsecrated and has been showing signs of ageing in recent years. Restoration work is planned, and geophysical investigations of the area around the chapel have been commissioned. In this article, we propose a robust methodology combining aerial and terrestrial measurements in the visible range with surface prospecting methods. Compiling all the measurements within a perfectly georeferenced 3D model allows the joint analysis of the results of different physical measurement methods to provide unexpected architectural and archaeological information. Photos were taken from the ground and using a drone to build photogrammetric models of the interior and exterior of the chapel. Ground‐penetrating radar (GPR) and electrical resistivity tomography (ERT) were the two survey methods deployed in the area surrounding the chapel. The geophysical measurements clearly reveal traces of apses—which have now disappeared—at the crossing of what would have been the building's transept, which match up with the filled‐in openings that are present. The existence of these apses can only be assumed from inside the chapel. The resistivity anomalies are perfectly correlated with the radar anomalies and allow new hypotheses to be formulated about the original structure of the chapel. Finally, mapping the local geology of the surroundings based on a geophysical survey provides crucial information about the history of the church's construction. Bringing this unknown architectural element to light and carrying out precise mapping of the local geology surrounding the chapel constitute a major breakthrough, as this will make it possible to improve our knowledge of the history of the chapel, in particular its origins, through research based on archaeological surveys. [ABSTRACT FROM AUTHOR]