Geoelectrical Measurements Research Articles

Electrical Resistivity Tomography and Boreholes Data to Investigate the Near-Surface Structure under the Campus Area of Çanakkale Onsekiz Mart University, Çanakkale, Turkey (Türkiye)

We study the soil foundation underneath the Çanakkale Onsekiz Mart University (ÇOMU) campus, Çanakkale, Türkiye by employing the electrical resistivity tomography – ERT supported by 27 boreholes data. The studied area taking place in southwest Marmara region was historically affected by large earthquakes () created by the North Anatolian Fault system. The boreholes data show that the near surface structure beneath the ÇOMU campus is made of mostly silty sands and marls. A high sensitivity resistivity instrument is used to collect the field data in which nine ERT profiles reaching lengths as long as 315 m are utilized. The current geoelectrical measurements are simulated by using two numerical models to estimate the inversion depth sensitivity from which it is found satisfactory in the depth range 0-30 m and then somewhat decreasing. The observed electrical resistivity values are in the range 2-160 W m. The geoelectrical structure corresponding to the silty sands are represented by low resistivities (<20 W m) while the high resistivity (>40 W m) depth sections are associated with the marl units. The resistivity structure beneath the ÇOMU campus is complex where both low and high resistivity depth sections reside side by side. The groundwater and clay mineralogy contribute to the broad changes in the subsurface resistivities. The groundwater flow below the steep terrain of the ÇOMU campus causes low resistivities (<10 W m) deeper than 10-m depth. The boreholes data superimposed on the two-dimensional (2-D) ERT profiles show consistency with the resistivity-depth distributions at corresponding depths.

Identification of Slip Surface Using Geoelectric Methods in post Cianjur Earthquake Landslide

Abstract The landslide occurrence after the 2022 earthquake was influenced by the geographical location of Cianjur Regency, located at the foot of Mount Gede, so the morphology of the highland relief is dominant. An earthquake measuring 5.6 on the Richter scale due to the movement of the Cugenang Fault triggered landslides at various points, one of which was in Cugenang District. This research aims to identify the slip surface of landslides in Cugenang District using the geoelectric method due to the 2022 Cianjur earthquake. This method is used to map subsurface resistivity values, producing 2D modeling. Surface slip inference is estimated at significant differences in subsurface resistivity values. The results of the interpretation of geoelectric measurements show the detection of slip surfaces at varying depths from the surface ranging from 5 to 15 meters, a distance of 20-90 meters from the first electrode with resistivity distribution values ranging from 0.01 Ωm to 155 Ωm. Consequently, the contact is considered to be the interface between the tuff breccia and the clay layer. This finding is confirmed by the shape of the layer which is thought to function as a sliding surface, which shows a concave/rotational shape following the slope in the geographically corrected 2D modeling.

Application of Experimental Configurations of Seismic and Electric Tomographic Techniques to the Investigation of Complex Geological Structures

The main purpose of this study is the subsurface investigation of two complex geological environments focusing on the improvement of data acquisition and processing parameters regarding electric and seismic tomographic techniques. Two different study areas, in central–east Peloponnese and SE Attica, were selected, where detailed geological mapping and surface geophysical survey were carried out. The applied geophysical survey included the application of electrical resistivity tomography (ERT), seismic refraction tomography (SRT) and ground penetrating radar (GPR). The geoelectrical measurements were acquired with different arrays and electrode configurations. Moreover, various types of seismic sources were used at seventeen shot locations along the seismic arrays. For the processing of geoelectrical data, clustered datasets were created, increasing the depth of investigation and discriminatory capability. The seismic data processing included the following: (a) the creation of synthetic models and seismic records to determine the effectiveness and capabilities of the technique, (b) spectral analysis of the seismic records to determine the optimal seismic source type and (c) inversion of the field data to create representative subsurface velocity models. The results of the two techniques successfully delineated the complex subsurface structure that characterizes these two geological environments. The application of the ERT combined with the SRT are the two dominant, high-resolution techniques for the elucidation of complex subsurface structures.

Determination of Rock Properties Based on Electrical Resistivity Tomography (ERT) in Taebenu, Kupang, East Nusa Tenggara

Determining rock properties is very important for various needs in engineering design. It requires samples of soil and rock that are representative enough for laboratory test. The effort to obtain rock properties through laboratory testing is arduous, therefore, it is anticipated that geophysical technique may be able to ease the process without reducing the quality of data. This research aims to determine rock properties based on resistivity. The rock properties data (stength, wet density, moisture content) was obtained through laboratory test on soil and rock samples from a drilling activity, while the resistivity data was obtained by using geoelectric measurement at the drilling locations as the trajectories. There were 10 boreholes with the depths varying between 30-100 m, while geoelectric surveying depth of investigation reached to about 80 m with a 500 m trajectory. The research was conducted that the study area is covered with Quaternary deposits which are mainly consist of clay and pebble sediments. A statistical method was performed to analyze the relationship between rock properties and resistivity. The result shows that in Quaternary rocks, there is sufficient evidence to conclude that there are significant linear relationships between resistivity and strength as well as natural moisture content, but not for wet density. This approach to the relationship of resistivity and rock properties can be utilized in geotechnical analysis for various purposes. The results of this analysis can be used as a reference when carrying out any future geotechnical analysis by combining resistivity measurements within the same study area.

IDENTIFICATION OF HYDROTHERMAL DISTRIBUTIONS USING THE WENNER-SCHLUMBERGER CONFIGURATION GEOELECTRIC METHOD IN LEMEU VILLAGE, LEBONG REGENCY, BENGKULU

The hot spring pool, Lemeu Village, Lebong Regency, is one of the geothermal fields. This research aims to identify the study area's geothermal potential and lithology. This is illustrated by the correlation method of resistivity and electrical conductivity values of rocks based on geoelectric measurements. This research uses the Wenner-Schlumberger configuration geoelectric method, as many as four tracks spread around the hot spring hill with a length of 480 meters, which are used to see variations in resistivity values that can indicate the presence of hydrothermal potential. The result is a 2D Resistivity model processed with Res2DinvX32 software. Based on the interpretation results, the subsurface rock lithology in each track is relatively similar in color, texture, grain size, and composition because it is around the hill. The Hulusimpang formation consists of clay, silty sand, tuff, andesite, basalt, and granite. Hydrothermal is found on lines 2 and 4 with resistivity values of 7.3 and 10.1 Ωm at a depth of 26 meters. Geothermal potential in the research area is divided into several temperature categories; some have low, medium, and high temperatures. In the research area, tracks 1 and 3 have low temperatures.

Geophysical Description of a Groundwater Aquifer Using the Combination of Geoelectric Measurements and Sub-Bottom Profiling

Geophysical Description of a Groundwater Aquifer Using the Combination of Geoelectric Measurements and Sub-Bottom Profiling

Interpretasi Material Pada Rancang Bak Ukur Skala Laboratorium Dengan Pendekatan Konfigurasi Wenner, Wenner – Schlumberger dan Dipole-dipole

Geoelectric measurements have been carried out using multichannel ResistivityMeter (Geores) tools with Wenner, Wenner-Schlumberger, and Dipole-dipole Configuration approaches on the influence of materials arranged in a laboratory-scale measuring tub design with dimensions of 194x184x80 cm. The measured method is the variation in resistivity value against each trajectory of the material. The method used is the variation of resistivity values for each path of the material that has been arranged in a laboratory scale measuring design. Geoelectric measurements were carried out on 7 lines (5 line in the West-East direction and 2 line in the North-South direction). The spacing between the electrodes of each line is 10 cm with 16 electrodes in one line so that each line has a length of 160 cm or 1.6 m which corresponds to the length and width dimensions of a laboratory scale measuring design. The electrode arrangement parameters are constant with respect to changes in the configuration selected from the geores parameters during geoelectric measurements. The measurement results showed that the identified depth reached 31.2 cm. The low resistivity value category has an interval of 374-4,397 ohm.meters at a depth of 0-12.5 cm, which is the influence of building sand material containing water and soil, while the depth interval is 12.5 - 31.2 cm ohm.meters (material category that is influenced by 2 iron rods, tin tailings sand, granite, gravel) with resistivity values ranging from 12,378–67,498 ohm.meters. From experiments on the influence of the resistivity values of the three Wenner, Wenner-Schlumberger, and Dipole-dipole configurations, it was obtained that the smallest absolute error resistivity value in the Wenner configuration was 5.01% against the overall average absolute error resistivity value of 10.16%.

Groundwater Potential of the East and North Sides of Gunungmasigit Village: A Case Study

The purpose of this research is to conduct a groundwater survei by analyzing the availability of groundwater on the east and north sides of Gunungmasigit Village, Kec. cipatat, kab. west bandung (case study: PPSDM Geominerba field campus KESDM). The aim of this study was to determine the potential for groundwater in the northern area of the PPSDM Geominerba Field Campus and to find information regarding the absence of groundwater after drilling was carried out in 2019 in the area on the east side of the PPSDM Geominerba Field Campus. The research administrative area is located in Gunungmasigit Village, Kec. Cipatat, Kab. West Bandung (PPSDM Geominerba field campus KESDM). The author will focus more on the end of Cipatat-1 (north side) on the map, where it is located in the gate area of the Geominerba PPSDM Field Campus. This study uses the geoelectrical measurement method. One of the geoelectrical methods is the resistivity or resistivity method. This method studies the subsurface structure based on the different resistivity values in the rock with depth. Data analysis used IPI2WIN Software with track 1 having a length of 200 meters and track 3 having a length of 400 meters. In the results of Cipatat-1 it is suspected that there is a water-carrying layer at a depth of 11.9 – 45.9 m. Meanwhile, the results of Cipatat-3 suggest that there is a water-carrying layer at a depth of 26.3 m.

Investigation of groundwater availability and geoelectric analysis to anticipate the scarcity of clean water in urban areas

The need for housing makes suburban areas of Jakarta such as Tangerang Regency, Indonesia, a location that continues to grow. AG Housing is a developer in the area that continues to build housing. In housing development, it is very important to pay attention to the magnitude of water needs, both domestic water needs and non-domestic water needs. A problem that often occurs is that housing developers do not take into account the long-term water needs of their residents, especially in water-scarce areas. Developers often do not check the condition and location of water content in the soil, resulting in water drilling being inefficient and wasteful. The aim of this research is to predict the clean water needs of residents of a housing complex and assess the condition of the water supply below the ground surface using the properties of electric current by flowing DC electric current. The method used in this research is a survey method and geoelectric analysis. This approach involves harnessing the characteristics of electrical current and directing it into the earth. Geoelectric measurements took a sample of 19 Vertical Electrical Sounding (VES) measurement points with North South and East West trajectories in the area. The research results show that there will be an increase in population and an increase in water demand in TA Housing in the next 20 years. Geoelectrical analysis shows the type of soil and rock below the ground surface that will be used as a housing location. Geoelectric testing showed 8 potential points as drilled well locations with a sand layer thickness of between 36.26 m – 62.28 m, while the depth from the ground surface was between 1.01 m – 70.00 m.

Determination of groundwater potential using geoelectricity in Tanah Bumbu, South Kalimantan

This survey was conducted to determine the distribution of groundwater in the Tanabumbu area of South Kalimantan. In this study, we aim to obtain the resistivity of soil layers using the Wenner geoelectric method and his one-pass, two-point dipole-dipole configuration. Field survey data were processed using RES2DINV software. Measurement data results are available in the form of 2D resistivity cross visualizations that are analyzed to determine groundwater distribution. In addition, we performed a comparative analysis of the accuracy of geoelectric measurement results using the results of data with different configurations. Based on the results of geoelectric measurements, we are able to find the aquifer location related to a high probability of groundwater.

Studi Keandalan Geolistrik Dalam Identifikasi Kebocoran Embung: Studi Kasus Embung Wolo, Sulawesi Tenggara

Small dams are vital for supporting water resource conservation. The reservoir stores water from several water sources, especially in the rainy season, so that it remains available in the dry season. Some reservoir infrastructures were built using earthen fill materials located around it. This condition is very vulnerable to disasters, ranging from seepage to collapse. It is important to evaluate the safety of all potential dangers to minimize the risk of disasters. One method that can be used is the geoelectric method, which allows us to analyze the resistivity properties of the soil, but the reliability of this method needs to be further evaluated. This research aims to determine the reliability of geoelectric in identifying potential leaks in reservoirs. Geoelectric measurements were carried out at Wolo Small Dam using the Wenner-Schlumberger configuration with 32 electrodes at 2.5 m. Data collection was carried out at the top of the small dam so that it could provide the condition of the soil layer of the embankment material in the longitudinal direction. Validate the measurement using the results of previous research. The results of the analysis show that there are differences in lithology in the body of the reservoir, which indicates differences in the quality of work during construction. The interface between these two surfaces can lead to leaks. Apart from that, the analysis results also show the potential for piping in the reservoir. The location of the potential piping area is not far from the results obtained in previous research at the same location. This shows that geoelectric is quite capable of being a tool that can be used to identify leaks in reservoirs or other water structures. Of course, the combination of geoelectric and other soil testing will provide better results in anticipating disasters caused by small dam leaks

Geoelectrical and Remote Sensing in the Characterization of the Pan-African Meta-sedimentary Basement Aquifer Systems: A Case Study at Nkoteng-Elap, Central Region of Cameroon

Abstract Nkoteng-Elap, a hamlet in the Central Region of Cameroon (Central Africa), has water issues, particularly with access to drinking water. The current study aims at (1) mapping the fracture networks of aquifers in the conceptual hydrogeological model and (2) delimiting the groundwater potential zones of the study area. A study combining remote sensing and geoelectrical measurements was carried out along profiles sub-perpendicular to the elongation of the geological bodies. Borehole and field geology data were used to validate the results obtained. The findings point to more than 300 linear structures about 0.065-74.89 km long, with two main directions: N80-100°E and N30-50-70°E. According to the Electrical Resistivity Tomography approach, there are three (03) geoelectric levels: conductive (less than 500 Ωm), semi-resistive (6500-12500 Ωm). resistive (more than 12500 Ωm), and resistant intrusive body (2050 Ωm). Existing drillings display three main lithological formations: the alteration zone, the fissured/altered zone, and micaceous quartzite. The correlation between the ERT data and drilling data reveals that the fissured or altered zone observed at 50 m is potentially aquifers. This structure is characterized by medium resistivity values (6500 Ω.m), flow rates of 1 to 3 m3/h for positive boreholes, and by low resistivity values (500 Ω.m), flow rates less than 1 m3/h for negative boreholes. The final map is categorized into five classes: very good, good, moderate, poor, and very poor groundwater potential zones. These results can help find basement aquifers and be useful in the planning and management of groundwater resources in a meta-sedimentary context.

Geophysical, geotechnical, and vegetation characteristics in landslide areas in Pujon and Ngantang, Malang Regency, East Java

One of the efforts to manage the risk of ground movement is to identify landslide-prone area characteristics. This study aimed to investigate the geophysical, geotechnical, and vegetation characteristics of landslide and non-landslide areas. This study adopted the resistivity geoelectric method to identify the type and structure of subsurface materials in landslide and non-landslide regions in Pujon and Ngantang, Malang Regency. Measurements in this study were done in four locations. Each geoelectric measurement path at each location was determined to be 100 m long. The electrodes were spaced apart by 10 m for measurements between the current electrode and the potential electrode. The dipole-dipole configuration of the geoelectric survey trajectory is determined based on the former landslide event to predict underground material. In addition, an investigation of geological, geotechnical, and vegetation characteristics was carried out. The results showed that the geophysical, soil, and vegetation characteristics of the landslide and non-landslide slopes were similar. The geophysical characteristics of the soil in all study locations indicate the presence of a slipping surface, which makes the land prone to landslides. The slipping plane was formed due to differences in the types of rocks between the surface and deep layers. The existence of vegetation has an important role in landslide management. Non-landslide areas tended to have denser tree vegetation and a higher number of shrub species.

The Effect of Water Below the Road Surface on Surface Distress Index (SDI) Values in the Road Condition Survey (RCS) Method

The results of the road damage assessment will reveal the Surface Distress Index (SDI) value according to the Bina Marga method (potholes, cracks and rutting). To determine the effect of subsurface water on road damage, geo-electrical measurements were carried out at road locations where it is estimated that there is subsurface water. At the location of the road segment, the damage value is then compared between the road with normal conditions SDI=aNx±ε and the road with water below the road surface. The results of the SDI value are then compared with the number of tracks of heavy vehicles (N) according to Equivalent Single Axle Load (ESAL) and the area of distribution of water below the surface (Aw). So it is expected to know the correlation model between road damage and the influence of water under the road surface surface SDI’=kAwn. These results will also be used as additional damage assessment items in the new damage assessment method based on the Bina Marga method.

Two-Dimensional Modeling of Leachate Distribution in Batu Layang Landfill on Peat Soil using Geoelectric Method

The open dumping system implemented by the Batu Layang landfill can produce leachate, contaminating groundwater around the landfill. Groundwater contaminated with leachate, if used by the community, can cause health problems. Therefore, management efforts were needed, such as subsurface leachate modeling. This study aims to model the distribution of subsurface leachate in 2 dimensions. The modeling of leachate distribution below the soil surface used the Wenner configuration geoelectric method. The number of geoelectric measurement paths was two paths. The length of each track was 195 m, with a distance of 5 m between the electrodes. Data obtained from resistivity values were analyzed using the Res2Dinv application. The calculation of leachate discharge used the water balance method. Based on the inversion results using the Res2Dinv software, the resistivity value of leachate-contaminated soil in line 1 was 1.19-9.43 Ωm, and track 2 was 0.5-10.2 Ωm. The leachate resistivity value was <10 Ωm because the leachate contains inorganic minerals (metals), so the resistivity value was low. Land contaminated with leachate was estimated to be spread as far as 195 m. The most profound leachate depth was estimated at 39.4 m. Batu Layang Landfill leachate discharge in Zone E averages 4 m3/day.

Interpretation of the Availability of Springs in Labuang Rano Village with a Geophysical Approach

Geologically speaking, Labuang Rano Village, Mamuju City area is composed of rocks from the Adang Volcano Formation. Based on the results of the site survey, it was found that there is a spring with a slight discharge. The emergence of these springs is not yet known, so further analysis is needed. An approach used to determine subsurface conditions is the geophysical approach, especially the geoelectric method. This study aims to analyse the subsurface geological conditions using geoelectric to find the factors that influence the emergence of springs. Geoelectrical measurements, observations of rock outcrops, and the findings of previous research are used as data sources. The results of the analysis show that the subsurface geological conditions consist of 3 layers. The topmost layer is tuff rock, the 2nd layer is volcanic breccia and the 3rd layer is andesite rock. Based on the resistivity cross-section, it can be seen that there is a fracture that cuts vertically in the tufa rock layer from a depth of 13 m to the surface in a northeast-southwest direction. Thus, it can be concluded that the emergence of springs at the study site was caused by a fracture that cut the tufa rock layers vertically from a depth of 13 to the surface. The fracture which is the medium for groundwater to emerge onto the land surface forms a spring.

Fracture System Characterization by Pressure Probe

Pressure Probe (PreP) is in effect a simplified penetrometer: it measures the mechanical resistivity of the soil at shallow depths dropping the probe always from the same height. The resolution of this technique is very good. It is able to detect e.g., fractures due to their decreased mechanical resistance if they are covered, but in a shallow depth with a reasonable sampling distance. An example will be demonstrated where fracture system of a slowly-moving landslide was characterized enabling also its delineation. In spite of that its maximal penetration is only about 0.5 m it may also give information from remarkable depths in case if fractures reach close to the surface indicating the borders of geological structures in larger depth. An example from India will be shown to present such results. All results have been verified by geoelectric measurements. PreP may also indicate any kind of hidden holes indirectly.

Identification of Alteration Zones Based on Resistivity and Induced Polarization Geoelectric Survey

Air Putih, Lebong Regency's geothermal field, is near gold mining. The relationship between the two can be illustrated in the type of rock alteration. The study aims to identify the rock alteration zone caused by the Air Putih, Lebong Regency geothermal system. It was described by the correlation of rocks' resistivity and chargebility values based on geoelectric measurement. Two tracks spread along the Air Putih tour, with a track length of 240 meters, were used to see variations in resistivity and chargeability values and the depth of geothermal potential due to deeper current penetration to determine the alteration zone in the study area. The results of field measurements are in the form of 2D models processed with Res2DinvX64 software. According to analysis, the subsurface rock lithology in the research area is relatively the same because the location of the two measurement lines is still close together; namely, there are wet valley rocks and alterated rock layers. Pores cause rock layers found in conductive areas in the rock filled with fluid or water at high temperatures. It is evidenced by the detection of manifestations on the surface in the form of warm soil, warm rocks, steamy soil, and small holes containing water grains. The higher the temperature and pressure, the lower the value of rock-specific resistance. At the Air Putih tourist area of Lebong Regency, it is found that it is a zone of prophylitic alteration containing several minerals of andesite lava, breccia, tuff, and soil.

Measuring Groundwater Flow Velocities near Drinking Water Extraction Wells in Unconsolidated Sediments

Groundwater is an important source of drinking water in coastal regions with predominantly unconsolidated sediments. To protect and manage drinking water extraction wells in these regions, reliable estimates of groundwater flow velocities around well fields are of paramount importance. Such measurements help to identify the dynamics of the groundwater flow and its response to stresses, to optimize water resources management, and to calibrate groundwater flow models. In this article, we review approaches for measuring the relatively high groundwater flow velocity measurements near these wells. We discuss and review their potential and limitations for use in this environment. Environmental tracer measurements are found to be useful for regional scale estimates of groundwater flow velocities and directions, but their use is limited near drinking water extraction wells. Surface-based hydrogeophysical measurements can potentially provide insight into groundwater flow velocity patterns, although the depth is limited in large-scale measurement setups. Active-heating distributed temperature sensing (AH-DTS) provides direct measurements of in situ groundwater flow velocities and can monitor fluctuations in the high groundwater flow velocities near drinking water extraction wells. Combining geoelectrical measurements with AH-DTS shows the potential to estimate a 3D groundwater flow velocity distribution to fully identify groundwater flow towards drinking water extraction wells.

Simulation of Biophysicochemical Characteristics of the Soils Using Geoelectrical Measurements near the Sewage Station, Assiut City, Egypt

Numerous farmers regularly irrigate their farms with inadequately treated sewage water pumped from the sewage system in the Arab El-Madabegh district of Assiut City, Egypt. According to previous studies, long-term irrigation with partially treated sewage water resulted in significant changes in the physicochemical properties of soil. The principal goals of this study are (1) to infer empirical equations between geoelectrical resistivity measurements and certain biophysicochemical parameters of some soil samples, and (2) to use these empirical equations to calculate the biophysicochemical parameters of the unknown samples for the same location. For this purpose, 27 soil samples at different depth levels (0 to 25, 25 to 60, and 60 to 90 cm) were collected from eleven locations at the sewage station. Physical properties including water content and particle size distribution, chemical properties including soil pH, electrical conductivity (EC), and the heavy metals concentrations, biological properties including total coliform counts, and geoelectrical resistivity measurements were estimated and analyzed for these samples. Electrical resistivity measurements and biophysicochemical properties were cross-correlated using the exponential trend line to fit the cross-correlated data, and the empirical relationships were obtained. These empirical relationships in conjunction with the measured electrical resistivity measurements were used to calculate the biophysicochemical values of the other three random soil samples. The biophysicochemical values of the former three samples were measured by the same normal procedures as 27 samples. Then, the calculated values were correlated with the measured ones. Good correlations between the estimated and the measured values for biophysicochemical features were obtained. Therefore, this method can be employed to calculate the biophysicochemical parameters for any unknown samples that have the same geological conditions for estimating and monitoring soil contamination.