Self-potential Values Research Articles

An Integrated Geophysical Investigation for Detecting Seepage-prone Zones in the Basement of a Building

The underground basement of a building is highly affected by anomalous seepage problems. Detection of seepage-prone regions through and around buildings becomes a need in other to sustain their stability. It is of great importance as well to have targeted remedies. However, traditional methods for examining these areas are often destructive and expensive, compelling the use of non-destructive geophysical techniques. This work aims to utilize and demonstrate the hands-on application of ground penetrating radar (GPR) and self-potential (SP) methods as an innovative combination to study seepage-prone zones in the basement of a building. Simulated responses of various seepage zones have been generated based on several significant factors. For better visualization, all 2D radargrams of a block were combined to produce a 3D model using GPR Slice software to distinguish various features at different depths. Higher positive SP values show the presence of high moisture or seepage-prone regions. Conclusively, the combined geophysical method of GPR and SP is trustworthy for conducting a quick and effective inspection of seepage-prone regions and probable source points for detailed characterization of the basement of a building. Keywords: GPR, SP, Geophysical methods, Seepage, Basement.

Geometry, Extent, and Chemistry of Fermentative Hot Spots in Municipal Waste Souk Sebt Landfill, Ouled Nemma, Beni Mellal, Morocco

The presence of fermentative hotspots in municipal waste dumps has been reported for several decades, but no study has focused on their size and shape. The uncontrolled landfill of Soub Sekt, covering an area of about 8 hectares in the Tadla plain in Morocco, is the source of a permanent pollution plume in the groundwater, detected by self-potential (SP) measurements. The study aims to detect and characterize these hotspots as well as the leachates that form within them. These hotspots are typically circular and smaller than 3 m in size, and they are concentrated within recent waste deposits. Intense electron transfer activities, particularly during redox reactions leading to metal solubilization, result in very low SP values (down to −60 mV), facilitating their detection. Several successive field campaigns suggest that they are active for 2–3 weeks. Due to the low permeability of the soils, highly mineralized leachates (average Electrical Conductivity 45 mS cm−1) rich in organic ions accumulate on the soil surface at the base of the waste windrows. There, they evolve by concentration due to evaporation and oxidation due to slow diffusion of atmospheric O2. Despite the small size of the hotspots generating the leachates, the accumulation of leachates in ponds and the low soil permeability limits the percolation rate, resulting in moderate but permanent groundwater pollution.

New Insights into the Gold Mineralization in the Babaikundi–Birgaon Axis, North Singhbhum Mobile Belt, Eastern Indian Shield Using Magnetic, Very Low-Frequency Electromagnetic (VLF-EM), and Self-Potential Data

The North Singhbhum Mobile Belt (NSMB) in the eastern Indian shield is an excellent example of a diverse lithological domain with multiphase shear/fracture zones. It is a well-acknowledged prospective region known for various mineralizations, e.g., Cu, Au, U, and Fe. The present study was conducted in the Babaikundi–Birgaon Axis (a shear and fracture zone within NSMB) within Babaikundi village. The study suggests that anomalous zones are possibly related to gold-associated sulfide mineralization using photomicrography and geophysical methods such as magnetic, self-potential (SP), and very low-frequency (VLF) electromagnetic (EM) methods. Photomicrography on quartz samples and Scanning Electron Microscope (SEM) Backscattered-Electron (BSE) images show that gold particles are present in the quartz reef vein in Babaikundi. Magnetic data are presented in the total magnetic intensity (TMI), upward continuation, and analytical signal maps. VLF-EM data were analyzed using different processing techniques to delineate anomalous auriferous zones. Furthermore, the SP data were inverted using the Particle Swarm Optimization (PSO), Very Fast Simulated Annealing (VFSA), and Genetic Algorithm (GA) approaches for comparative study of the resultant model parameters and their suitability considering a 2D inverted resistivity section derived using VLF-EM. The photomicrography study indicates the existence of gold/ pyrite/pyrrhotite within the Babaikundi–Birgaon axis, which corresponds to a low magnetic anomaly based on a magnetic study; a high current density, a high Fraser value, and a low resistivity based on the VLF-EM study; and a negative SP value was found based on the SP study. The combined study generally supports mapping auriferous zones and demarcates the Babaikundi–Birgaon axis within the Babaikundi–Birgaon area.

REVIEW OF IDENTIFIED SHORTCOMINGS IN AQUIFER VULNERABILITY ASSESSMENTS

Several studies have successfully carried out aquifer vulnerability evaluations using a combination of geophysical and biogeochemical methods. Unfortunately, some identified shortcomings have often led to inaccurate assessments. This review attempts to identify some of these drawbacks and suggest better ways to improve upon analysis and interpretation of results. Articles reviewed were sourced publicly and subjected to systematic analysis based on fundamental principles. The outcomes of each analysis were discussed, among which was a study that applied Ohmega Resistivity meter to acquire Self-Potential (SP) data without specifying the nature of electrode used. The result indicated large SP readings ≥200mV attributed to high fluid flow. According to analysis, when copper stakes are used, spurious SP readings occur in contrast to lower SP values of roughly 10 mV when suitable non-polarizable electrodes of Cu/CuSO4 porous pots are utilized to collect SP data. The review made clear the importance of providing detailed explanation of the nature of materials used. Another study solely collected samples for groundwater quality assessments during dry season, ignoring the effects of seasonal variation on water parameters. This must have had an impact on the results of the investigations. Research examined the aquifer problems in Gosa area of Abuja, utilizing only the Vertical Electrical Sounding (VES) technique. The study suggested basaltic intrusion as probable cause of borehole failures in the area. A different research which incorporated VES and data from the hill-shaded Shuttle Radar Topography Mission (SRTM), suggested insufficient interconnectivity within the fractures as conditions controlling groundwater occurrence in the area. The study illustrated the need for integrating geophysical methods for effective target detection. To map the infiltration of leachate into the subsurface, a study applied only the VES technique. Studies, however, showed that the VES method only provided average resistivity readings, suppressing some features. The study suggested the combination of VES and 2-D imaging for more accurate results. Another study obtained data via the ADMT Groundwater Detector. At the interpretation stage, the author interpreted ADMT data as VES, which was perceived as inaccurate as their principles and methodologies are different. Another study was noted to have presented results without categorizing the Aquifer Protective Capacity (APC) rating in percentages (%). It was assessed that a framework that accurately categorized the APC of each transversal using common statistics guidelines would have made it simpler to understand and aided decision-making. Future research is advised to take some of the noted flaws into account in order to enhance data processing and interpretation.

Assessment of Unconfined Aquifer Hydraulic Characteristics Using Self-Potential Method: Case Study in Laylan Sub-Basin, Kirkuk, Iraq

This study aims to evaluate the hydraulic characteristics of the unconfined aquifer in the Laylan area, Kirkuk, Iraq. The pumping test was carried out on four wells in the Laylan area. all wells penetrate the quaternary sediment, which consists of sand, gravel and clay, the monitoring of the change in the groundwater table was carried out by the groundwater depth detector and the self-potential device, as the purpose of this study was to find an alternative to the traditional methods that monitor the draw down during pumping test, whose use is often accompanied by many obstacles and especially most of the wells belong privately to the farmers, where the goal was to find a relationship between the self-potential readings and the change of the water depth that measured by groundwater depth detector. a mathematical relationship was obtained that links the values of the two variables. In addition, the conductivity value was calculated by substituting the self-potential value in the equation to find the draw down values and then entering into the aquifer-win program. The geophysical self-potential value is very sensitive to the groundwater level changes the correlation coefficient between each of them as in the wells (pw1, pw2, pw3 ) is 0.95,-0.83 and -0.86 respectively, It is a strong and inverse relationship. Transmissivity values for the wells PW1,PW2,PW3 ,PW4 were 12.32 m2 /day, 17.22 m2/day, 78.29 m2/d (10 m2/d) respectively and the hydraulic conductivity for the wells PW1, PW2, PW3, PW4 were 0.113 m/day, 0.21 m/day, 1.74 m/day, 0.25 m/day respectively the obtained hydraulic conductivity value was an approach to the hydraulic conductivity values obtained in the traditional methods. Therefore, the equation can be used in aquifers if it was in the same conditions as this basin. Therefore, the SP device can be considered a successful alternative to traditional measurement methods.

Correlation of 2D Electrical Resistivity and Self-Potential Methods for the Assessment of the Integrity of Goronyo Dam NW Nigeria

Abstract In this research, combined 2D electrical resistivity and self-potential (SP) methods were employed to locate anomalous electrical conductivity around the Goronyo dam in order to determine the condition of the embankment of the earth dam. The data were taken with the reference to resistivity and SP values using Wenner configuration. The results obtained from these techniques shows that the area was underlain by four stratigraphic layers, namely; clayey sand, wet sandy clay, laterite and partially weathered basement complex rock as compared with the resistivities of common rocks and borehole lithology of the area. The low SP (< 200 mV)/high resistivity zones in the overburden of profiles P1, P2 and P3 shows the presence of partially weathered basement complex rocks which was probably due to compactness and dryness around the dam. However, the zones of high SP (≥ 200 mV)/low apparent resistivity regions (z1 and z2) of profiles P1 (2 Ωm to 27 Ωm), P2 (3 Ωm to 25 Ωm) and P3 (3 Ωm to 14 Ωm) have revealed the weak zones associated with wet sandy soil. Results obtained from 2D electrical resistivity (z1) technique have correlated well with the results of SP sections (z2). These regions of weak zones occupied the x-distance along the profiles; P1/or S2 (120 m to 200 m and 250 m to 400 m), P2/or S2 (1 m to 156 m and 192 m to 400 m) and P3/or S3 (48 m to 400 m) with their corresponding depth y, ranging from 23 m to 30 m, 26 m to 30 m and 23 m to 30 m. Keywords: 2D Electrical Resistivity Tomography (ERT), Self-Potential (SP), Dam, Subsurface, Seepage, Condition

Study of Fluid Flow Movement by Using Self Potential Data

The Self-Potential (SP) method is passive method in geophysics which works based on the natural presence of an electric field on the surface due to anomalies below the surface. SP value on surface can be generated by fluid flow through rock pores or fractures. We study fluid flow movement in subsurface using the velocity value of fluid flow derived from SP values measured on surface. For that purpose, we carried out mathematical modelling, connecting the Helmholtz-Smoluchovsky’s electrokinetic potential gradient equation with Darcy’s law. The velocity of fluid flow depends on the intrinsic permeability of rocks, electrokinetic potential gradient and electrohydrolic conductivity constant. We tested derived velocity of fluid flow on the SP data from a pilot project test site. Study results show that fluid flow in vertical direction can be identified from SP data at locations where there are significant changes of positive and negative SP values. Fluid flows from a high SP value to a low SP value and this flow is opposite the positive SP gradient. The SP value at study site lie in the range -80mV to -160mV, whereas the value of the water flow velocity lie in the range 0.08 cm/s - 0.21 cm/s.

ANALYSIS OF ELECTRICAL CHARACTERISTICS OF MINING DESTRUCTION ON COAL SEAM ROOF AND FLOOR WITH SIMULTANEOUS DYNAMIC MONITORING METHOD

As the depth of coal mining increases, the water hazards in mining under the deep and complicated conditions become increasingly serious. The dynamic monitoring of roof and floor failure in the coal mining process under complex conditions is of great significance to the prediction of water inrush at the mining face and the improvement of coal mining methods. Based on the parallel electrical monitoring technology, and combining the dual-mode electrode data collection method, we monitor and research the geoelectric field characteristics of the full space of coal seam roof and floor at the coal mining face simultaneously. Additionally, we obtain the synchronous response characteristics of resistivity and self-potential of the coal seam roof and floor surrounding rock before and after the mining at the first time. Research findings are as follows. The dynamic change of the cross-hole resistivity monitoring of the roof and floor can show the dynamic variation of the inter-hole resistivity with the gradual advancement of the coal mining face. It can also demonstrate the development range of the roof and floor failure zone effectively. Besides, the degree of resistivity variations caused by the apical plate collapse is greater than the degree of resistivity change caused by the bottom plate rupture. Self-potential data can reflect the roof and floor rock and fissure expansion and closure forms, and the degree of rupture. The self-potential value of the apical plate in the study area is obviously higher than the bottom plate, and the self-potential change intensity caused by the apical plate rupture is obviously greater than the bottom plate rupture. Multi-parameters are used to synchronously and dynamically monitor the roof and floor mining damage of coal seams, which has real application value to guarantee the safe mining of the mining face.

GROUNDWATER POTENTIALS ESTIMATION USING SELF-POTENTIAL METHOD AS AN EARLY PREDICTION OF LAND SUBSIDENCE IN GAMPONG LENGKONG LANGSA CITY

The Self-Potential (SP) method was used to identify changes in the potential groundwater in the area of Gampong Lengkong, Langsa City. The data acquisition technique was carried out with a fixed base technique with a measurement count of four acquisition line. Research is conducted for two months that July and August are the same in order to monitor the changes in the SP value associated with the change of SP anomaly. Interpretation is done qualitatively and quantitatively. Qualitative interpretation through analysis maps of the isopotential contours compared between the first month and the second month of measurements in the field. The interpretation is quantitatively by assuming the source of the subsurface anomaly fix geometry models of cylinders or sphere is done by the inversion modeling using the Levenberg-Marquardt method. The results showed that there was a reduction in SP value in the second month, indicating the potential shortage of groundwater in the region. The decrease in groundwater potential is also shown in the inversion results where the result of the calculation of SP anomaly source parameters in the first month is estimated to be at 7.77 meters to 11.05 meters below the ground in the monthly measurements second.

Self Potential (SP) and Resistivity Methods of Discriminating Lithologies in a Landslide Areas of Ohafia Town, Nigeria

This research presents the application of geophysical self-potential (SP) and resistivity methods in evaluating subsurface phenomenon in Ohafia Area. Two communities were covered with three profile lines of 200 m spread occupied in each location. The data were acquired using ABEM SAS 300C Terrameter and later processed with EarthImager 1D inversion modelling software. Self-Potential values ranged from -107.8 to 112.3 mV in Amaekpu and -100 to 150 mV in Elu area. Positive SP values indicated lithologies with low permeability while negative SP values showed permeable lithologies. Six geologic layers were inferred for Amaekpu area while seven layers were inferred from Elu area. Layer 1, 3 and 5 are low permeable lithologies while Layer 2, 4 and 6 are permeable intervals in Amaekpu. In Elu, Layers 1, 3, 5 and 7 are having low permeability while Layers 2, 4 and 5 are highly permeable lithologies. Lithologic intervals inferred from inverted resistivity data which include sands, sandstones and gravels conformed with regions having negative SP values. Similarly, depth intervals identified as topsoil, siltstones and clay conformed with positive SP values.

Detection of the piping processes analyzed through the Self Potential method, in the peripheral area of the Dognecei Mountains

The water movement in the soil contributes to entrainment of particles of varying sizes, and over time, some tendency for the orientation of this flow may occur. In the areas with particular soil characteristics, an internal discrete drainage network appears, that manifests differently depending on the causative factors. The aim of the recording and monitoring of this concentrated water flow movement that contributes to soil erosion as a pipe network through a geophysical method is to understand its evolution. Using a method such as the Self Potential (SP) allows the study of the piping processes in a quantitative manner. In the peripheral area of the Dognecei Mountains, specifically near the Doclin village, it was analyzed one such area in which this process occurs.It was analyzed the evolution of a site in periods with different climatic parameters which are the ones that act as the active elements.The amplitude of the SP values (mV) differs based on the causative environmental factors, with negative values in the dry period and positive values when the soil is wet, the values having fluctuation up to 15 mV. The piping processes contribute to soil degradation and the knowledge of the areas affected by this processes and particularly of the factors influencing its occurrence can be achieved with good results by using the Self Potential method.

Landslide investigation using self potential method and electrical resistivity tomography (Pasanggrahan, South Sumedang, Indonesia)

Landslide is a geological event that occurs because the movement of slope-forming material in the form of soil, rock or combination of material type to a lower place due to the influence of gravity. The trigger factor of landslide in Pasanggrahan, South Sumedang, Indonesia is the increase of water content in the slope and the slip plane. The slip plane began to actively to turn on when the rainy season arrives. The infiltration of rainwater into slopes as an avalanche trigger can be detected by Self Potential (SP) method. SP measurements were performed to determine changes in subsurface water flow. SP data acquisition using fixed base technique and leap frog technique. The rocks in the research area that serve as the slip plane are clays associated with Volcanic Breccia. One of the geophysical methods that can identify the slip plane is the Electrical Resistivity Tomography Method. The ERT method can detect slip plane based on rock resistivity. Based on the local geology that has been correlated with the value of Self Potential and Electrical Resistivity Tomography, the following results are obtained: water table : (1 - 13) Ohm.m and SP value : (16 - 50) mV, clay : (72 - 100) Ohm.m and volcanic breccia: (171 - 550) Ohm.m.

Mitigation of Land Movement using Self Potential Method in Ling-Anjung Region Sumedang Regency

Land movement occurs due to reduced soil strength which is affected by water pressure. The Self Potential (SP) method is a geoelectric method that can detect well the flow of groundwater. The Self Potential method can also be used to detect the presence of debris flow in the form of weathered soil, tuff sand, cobble gravel and other rock fragments that have mixed with water. Based on the results of the SP measurement, debris flow has a medium SP with a value (3 - 12) mV, rock that has shifted (sandstone associated with andesite fragment) has a SP value < 2mV, while water seepage and water flow has an SP value (13 - 36) mV.

Detection and delineation of coal mine fire in Jharia coal field, India using geophysical approach: A case study

Coal mine fire is a serious problem in Jharia coal field, India. The coal mine fire can be detected with different techniques such as borehole temperature measurement, thermo-compositional analysis, remote sensing techniques, thermo-graphic measurement and geophysical methods. In this study, various geophysical methods were used to detect the surface and subsurface coal mine fires. Geophysical techniques used in the present study are apparent resistivity, self-potential (SP), magnetic method and thermography. Geophysical anomalies such as low SP value of \(-60\hbox { mV}\), high negative magnetic response and low apparent resistivity value helped us to detect and delineate the fire and non-fire areas laterally as well as depthwise. Furthermore, the thermography survey was carried out in the coal field using thermal imaging camera in order to substantiate the geophysical methods. This integrated approach was found to be more advantageous for the detection and delineation of surface and subsurface fire with respect to use of any specific techniques. Moreover, the level of threat towards the locality, national railway line was also assessed unambiguously using the above techniques. Hence, proper planning and implementation towards the mitigation of hazard can be achieved on the basis of the reported results.

Identification of Self-Potential Anomalies of a Diffusion–Absorption Origin

Diffusion and adsorption (DA) potentials are frequently the sources of self-potential (SP) anomalies, but they do not arouse practical interest in contrast to anomalies of oxidation–reduction and filtration origins. DA anomalies are common and geophysicists sometimes mistakenly consider DA anomalies as examples of filtration anomalies. Identification of DA anomalies is based on correlation of SP and apparent resistivity values along the same profiles. During the student geophysical training workshop for students of the Moscow State University (Aleksandrovka village, Kaluga Region) we obtained profiles with SP and resistivity anomalies with good correlation between them. This makes it possible to consider such SP anomalies as a result of DA processes.

Experimental study of the self-potential anomaly caused by coal fires

Self-potential method has been used to detect coal fires for decades. However, the origin of self-potential anomaly relating to coal fires is still unclear. In this paper, we first analyze three possible sources of self-potential anomaly that relating to coal fires, i.e., the thermoelectric potential, the redox potential and the streaming potential, among which the streaming potential is negligible. Then, an experimental system is designed to research the above-mentioned three possible sources, in which six experiments are conducted finally. The results verify the existence of the thermoelectric potential and the redox potential. The self-potential that measured on the surface increases with the increase of temperature of the heat source, but decreases dramatically with the increase of its buried depth. Furthermore, the redox potential reduces the total self-potential values on the surface.

SIMULASI HIDROTERMAL DAERAH KAWAH DOMAS DENGAN PEMODELAN KONTINU 2-D ANOMALI SELF POTENTIAL (SP)

Hydrothermal system research using Self Potential (SP) Method, 2-D DC Resistivity and surface temperature, has been done at Domas Crater (1700 masl). Potential anomaly which is associated with subsurface structure is obtained by SP measurement, whereas temperature measurement is done to get information about surface temperature distribution laterally and resistivity distribution of volcano structures is known by 2-D DC Resistivity measurement. Hydrothermal activities, which cause the existence of SP value, are modeled using this scheme modeling. This schema modeling is validated by comparing the value of SP model with field measurement. The shallow hydrothermal activities at Domas Crater are influenced by meteoric and subsurface water. The velocity of hydrothermal activities are about 10-9 - 10-7 m/s. 16.64% root mean square error is obtained by Comsol modeling, whereas 6.54% root mean square error is obtained by modeling using finite element method.

Dam Seepage Investigation of an Earthfill Dam in Warren County, Missouri Using Geophysical Methods

Electrical resistivity tomography (ERT), induced polarization (IP) and spontaneous potential (SP) data were acquired across and in proximity to a leaking earth-fill dam (Wolf Creek dam) in Warren County, Missouri. The objectives were to identify and map probable seepage pathways through the dam and to determine if the outlet works drainage pipe used in the construction of the dam was leaking. On the basis of the integrated interpretation of the acquired geophysical data two probable seepage pathways through the leaking earth-fill dam were identified and mapped. These two pathways are referred to as the Groin Leak and Water Fall Leak, respectively. The Groin Leak and Water Fall Leak seepage pathways are both characterized by relatively low resistivity and low chargeability. It is also concluded that there is high probability that water is leaking from the downstream end of the outlet works drainage pipe. The interpreted drainage pipe leak (Outlet works Leak) is characterized by relatively low resistivity, high chargeability and negative self-potential values.

Transport Processes in Porous Media by Self-Potential Method

A controlled diffusion/infiltration column experimental activity was carried out with the aim of monitoring the leakage of a salty water plume by time-lapse self-potential (SP) measurements. In particular, three tracer tests with different NaCl concentrations (6.00, 1.00, and 0.25 g L−1) were performed and all the measured SP signals showed a sharp reduction corresponding to the arrival of saline front with negative electrical potential values (−78.99±3.24 mV, −54.52±2.28 mV, and −24.12±1.21 mV) which decrease with increasing volume of tracer introduced into the column. Then, measured self-potential values were converted into salt concentration ones by the Planck-Henderson equation and sand diffusion(D)and longitudinal dispersivity (αL) values were estimated by modelling the transport equations in the COMSOL Multiphysics environment. Finally, the results show that measured and estimated NaCl concentrations are well correlated.

Characteristics of Resistivity and Self-Potential Anomalies over Agbani Sandstone, Enugu State, Southeastern Nigeria

The characteristics of the Resistivity and Self-Potential (SP) anomalies over Agbani Sandstone have been carefully and painstakingly carried out. The study was aimed at investigating the possible rock types and their mineralogical potentials. Data was acquired using the high resolution versatile ABEM SAS 4000 resistivity meter, employing the profiling method. Datasets were analyzed using the Excel toolkits. Interpretation was basically qualitative. Based on the resistivity interpretation, Agbani Sandstone is laterally limited in extent while the mineralization potential is high as a result of the high negative SP anomalies. The negative SP values range is -200mV to -500mV. This is practically indicative of a sulphide orebodies – possibly pyrite (FeS2). Comparative profile plots show that the observed zones of sulphide orebodies are within the gradational contact of Agbani Sandstone with Awgu Shale. Stream sediment analysis and rock geochemical study are recommended. However, the study has shown that contact zones of sandstone deposits are possibly ore enrichment zones.