Geoelectric Sections Research Articles

Geotechnical Characterization of the Subsurface Using Seismic and Electrical Resistivity Techniques in Mikinduri Meru County, Kenya

Abstract Geotechnical study of the Mikinduri area was conducted with the aim to establish the causes of landslides and ground subsidence during the heavy rainfall. Sounding curves, travel time curves, 2D geoelectric sections, and 2D seismic models revealed 3-5 lithologic units to a depth of 30-250m. The study established thick loose alluvium deposits mixed with clay to a depth of 0.3-15m on an impermeable sub-basement as the possible major trigger of the landslides witnessed during rainy seasons. The thick alluvium deposits are due to erosion. They have been transferred by the location of the Mikinduri area, which lies in the lower regions of the Nyambene domes. Geologically, the domes were formed during Mount Kenya volcanic series and parasitic activities between the early Miocene and late Pleistocene eras. Resistivity modeling revealed deep geologic structures, including possible intrusions extending from 50m deep and faulted regions to a depth of 60-150m in the central and northeast area of study. The faulted area is highly saturated, as revealed by the low resistivity values. The delineated top black cotton soils and alluvium deposit are 40-50% clay and have poor foundation bearing capabilities. In contrast, compacted gravel, silt, and compact basaltic rock basement have good foundation capabilities. Keywords: Geotechnical, characterization, subsurface, seismic, electrical resistivity, foundation, geoelectric layer, Mikinduri Meru, Kenya.

English

Vertical electrical sounding (VES) and 2D electrical resistivity tomography (ERT) employing the Schlumberger and Wenner configurations respectively were combined for groundwater exploration in parts of Enugu metropolis. The area is underlain by Enugu Shale and Mamu Formation. A total of twenty (20) VES and four (4) 2D ERT traverses were acquired in the study area. VES and 2D ERT data were processed and interpreted using INTERPEX 1X1D and RES2DINV respectively. Sounding curves shows dominant decrease in resistivity with depth while 2D ERT inverse model shows lateral variation in resistivity of the rock layers with lower resistivity at increasing depth. VES geoelectric layer sections show top sideritic clay - clay/shale sequence. Resistivity curve analysis also shows predominance of Q and K curve types. 2D map of aquifer layer resistivity, thickness and depth were constructed. Aquifer layer resistivity range from 2.00 to 190 ?m, while the thickness range from 10 to 75 m and a depth range of 23 to 150 m. The 2D ERT shows layer resistivity range of 0.1 to 250 ?m. Based on the combination of the two techniques for groundwater exploration in the study area, a water table depth of 18 m with a maximum drill depth of about 100 m was determined. However, it is recommended that the selection of point of drill should be on the low saturated regolith as observed on the 2D ERT sections.   Key words: Aquifer, groundwater, VES, 2D ERT, resistivity.

ЭЛЕКТРИЧЕСКИЕ СВОЙСТВА И ГЕОЭЛЕКТРИЧЕСКИЙ РАЗРЕЗ НЕКОТОРЫХ ОСАДОЧНЫХ ГОРНЫХ ПОРОД БАЙКАЛЬСКОЙ ПРИРОДНОЙ ТЕРРИТОРИИ ПО ДАННЫМ РАДИОИМПЕДАНСНЫХ ЗОНДИРОВАНИЙ

The specific electrical resistance (electrical conductivity) of some layered sedimentary rocks of the Baikal natural territory was measured by the method of radio impedance sounding in the VLF-LF ranges of electromagnetic waves. Their geoelectric sections are determined. Information about the geoelectrical section (GES) of sedimentary rocks of the Baikal natural territory can be used in engineering and geological surveys of the Siberia-Mongolia-China gas pipeline route, as well as in the analysis of the physico-chemical causes of the appearance of corrosion processes on long pipeline structures of the continental regions of Eurasia. The technique of radio impedance sounding can be applied to measure the electrical properties of various soils of a given territory within a layered model of a medium with a poorly and well conductive base.

Identification of Groundwater Bearing Zones Using Geoelectrical and Electromagnetic Techniques at Tourah Area, South of Cairo - Egypt

The complex geology of Tourah area, south Cairo is a serious challenge for groundwater exploration, where the risk of unsuccessful groundwater drilling excavation for industrial purposes is well dressed, raising the need for better geophysical subsurface detection and characterization approaches in terms of water bearing and aquitard zones. Datasets from the study area were acquired using integrated geophysical techniques comprising of one Dimensional Vertical Electrical Soundings (1D VES) and one Dimensional Transient Electromagnetic (1D TEM) as well as two-Dimensional Electrical Imaging (2D ERI) which was restricted to the available spreading space as well as subsurface infrastructure noise. The results of 1D VES and 1D TEM soundings detected three to five geoelectric layers used to generate geoelectrical cross sections and maps of resistivity, thickness, and depth to water bearing zone. Moreover, the 2D ERI inversion profiles were able to image the first three layers and the depth of the water bearing zone [A] with significantly greater resolution due to their higher lateral and vertical resolutions compared to the traditional 1D VES and TEM interpolated cross section. The integration of the three geophysical methods displayed a smooth distribution of both marly limestone and fractured shaly limestone and claystone bands water bearing zones [A and B]. Resistivity values of the water bearing zone [A] ranges from 0.1 to 24 Ω m, with average thickness of 4 to 12 m, and depth to water of 1.5 to 13.6 m. In addition, [zone B] is the main water bearing zone of fractured shaly limestone and claystone bands (2 to 14 Ω m) which is detected at deep depth of 40 and 75 m. Two normal fault systems inferred from 1D interpretation are considered responsible for local recharging of the main Eocene aquifer over the study area. In conclusion, the outlined water bearing thickness as well as limited sources of groundwater recharge indicate that these water bearing zones may not provide a sustainable supply for the industrial development purposes in the future.

GEORADAR AND RADIOIMPEDANCE DIAGNOSTICS OF THE SELENGA RIVER WATER AREA

The relevance of the work is determined by the fact that no radiowave methods have ever been used to study the water areas of rivers and lakes and their geoelectric sections within the Baikal natural territory (BNT) in winter time. The purpose of the research is to determine the electrical and geometric characteristics of the layered medium "ice – water – bottom soil" and the ice cover of the Selenga River on the BNT in the VLF-LF and VHF radio wave bands according to the data of instrumental radiophysical measurements by GPR and radio impedance methods, including the determination of the structure of the ice crossings over the Selenga River. Using the Selenga River as an example, consideration has been given to the results of combining VLF-LF and VHF methods of electromagnetic diagnostics of a layered medium in a wide range of radio waves (from tens of kilohertz to units of gigahertz). Radio impedance profiling and sounding in the VLF-LF bands with the IPI-300 equipment made it possible to determine the sub-bottom structure of the soil from the change in impedance and geoelectric section. GPR in the VHF band made it possible to differentiate the fine structure of the Selenga River in winter by thickness of snow, ice and water. The sounding involved the use of georadar "Oko-2" with antenna units "Triton" (central frequency 50 MHz), AB-400 (central frequency 400 MHz), AB-700 (central frequency 700 MHz), and AB-1700 (central frequency 1700 MHz). The thickness of ice of the road crossing in the Mostovoy microdistrict of Ulan-Ude city was 0.5–1.2 m – 0.1–0.2 m thicker than that beyond the road crossing. It was found that the presence of snow cover beyond the road crossing prevents the ice mass from freezing. Calibration sounding of ice with borehole drilling yielded ice dielectric constant ε=3.17. The specific electrical resistance (SER) of water from boreholes is 71–74 Ohm·m at a temperature of 1 °C. The methods used complement each other and provide a quantitative description of the object of research. The integration of various methods of radio wave diagnostics provides more detailed information on the structure of the layered medium "ice – water – bottom soil". The obtained results and the developed methods of radio impedance and GPR sounding and profiling of an inhomogeneously layered underlying environment in winter time can be used in engineering and geological surveys in the eastern and northern regions of Russia.

Geology and Correlative Analysis of Borehole Logs with Geo-electric Sections of Some Parts of Ibadan, Southwestern Nigeria

The property of rocks varies from one geological location to another or even disappears laterally, and these properties are important factors in determining groundwater quantity. This makes this research work focused on the correlative analysis of lithologies and borehole logs with geo-electric sections in the basement terrain of Ibadan, southwestern Nigeria, using Borehole logging and geophysical electrical method. Twenty-two vertical electrical sounding stations and borehole Logsare acquired within the study area with a maximum Schlumberger electrode separation of 100m. The data are interpreted qualitatively and quantitatively by partial curve matching and computer iteration to obtain the first-order geo-electric model parameters. The results of the geo-electric investigation reveal some lithological Layers such as topsoil, clay, weathered laterite basement, and fresh basement. At the same time, those from boreholes include topsoil, loamy soil, friable brown soil, clayey-sand, sandy-clay, laterite weathered basement/saprolite, and Fresh Basement. Electrical resistivity and borehole logs correlation revealed: poor, poor-moderate and moderate-perfect correlations based on a comparison between the number of lithological layers encountered from both vertical electrical sounding derived lithology and those from borehole and depth of occurrence. The depth of water struck grouped into three 0 - 45 m, 45 - 70 m, and 50 - 100 m to bring out the most favourable depth of aquifer potential while three yields categories 0.5-2 lt/s; 2 - 4lt/s and 4 -12 lt/s are observed with the above depth classification respectively. Good yielding fractures increase with depth in the quartzite regions but decrease with depth in both gneisses and the schist rock bodies. The correlations between geo-electric sections and borehole logs have shown that the geoelectric section obtained from the vertical electric section cannot totally be substituted for borehole logging but can serve as alternative means of classifying the sub-surface lithologies in the absence of borehole logging.

Geophysical studies of permafrost conditions of the Kangalassky coal mine dam

Problem statement. Geophysical studies of the ground dam body and base at the Kangalassky coal mine were carried out as part of monitoring related to the dam’s destruction, propagation of flank release fractures parallel to the ledge, and water seepage into the open pit. The main function of the ground dam is to protect the mining site from the inflow of surface water and preserve frozen rocks of the geological base. The mine workings of the coal mine are watered due to precipitation in the summer, snow melting and frozen rock thawing in the spring. Research objective is to assess the permafrost-ground conditions of the site according to geophysical methods and establish the boundaries of seepage flows that seep through the body and base of the ground dam. Methods of research. Electrical sounding at the dam site were performed by the electrical resistivity tomography method. The research was carried out with the Omega-48 equipment. Ground Penetrating Radar (GPR) study was carried out with a georadar of the OKO-2 series (AB-250M, central frequency 250 MHz). Georeferencing for comparative analysis of GPR parameters and positioning was carried out by the Geobox Fora Smart high-precision (geodetic) GNSS receiver. The cryogenic condition of rock was determined from the drilling data and FLIR SC660 thermal imaging camera data (device by the Shared core facilities of the Federal Research Center “Yakutsk Science Center SB RAS”, grant no. 13.TsKP.21.0016). Results. The results of GPR studies by the method of multi-season measurements in spring and autumn made it possible to objectively assess open pit permafrost conditions that reflect rock mass condition features (frozen or thawed rocks) and the position of the weakness zones (seepage areas and the presence of waterlogged soils). The analysis of geoelectric sections has identified anomalous areas with reduced electrical resistivity interpreted as zones of suprapermafrost surface water penetration into the embankment body with further dam base soil erosion. Possible surface waters migration routes and frozen rock degradation areas have also been identified. Scope of results. The described technique can be used at the enterprises of the mining complex in the North of Russia for engineering-geological and geocryological monitoring of mining and engineering structures.

The Geoelectric Section of the Lithosphere in the Central Southern Sikhote Alin Fold System along the Dalnerechensk–Nakhodka Bay Profile from MT Soundings

The Geoelectric Section of the Lithosphere in the Central Southern Sikhote Alin Fold System along the Dalnerechensk–Nakhodka Bay Profile from MT Soundings

Subsurface Investigation for Road Construction Using Electrical Resistivity Method along Oloko road, Apatapiti, Akure, Ondo State, Nigeria

Abstract Evaluation of the shallow geologic materials in terms of types, nature, and bedrock structure as possible causes of pavement failure was carried out along Oloko road Apatatpiti, Akure, Nigeria, using Schlumberger vertical electrical sounding and 2-D imaging dipole-dipole techniques. Three lithological layers, namely thin top soil, weathered layer and weathered basement, were revealed by the 2-D resistivity structure. Vertical electrical soundings were made at locations with a very low resistive medium typical of linear features such as fractures/faults at some distances on the 2-D resistivity structure. Four geologic layers, namely the top soil, clay/sandy clay, fractured basement, weathered/fresh basement, were identified by the geoelectric section. The geoelectric section and the 2-D resistivity structure revealed that the upper 0-6m, which constitutes the subgrade, has a low resistivity (36 Ωm to 108 Ωm) characterised to be clayey materials and suggestive of weak zones that might impair the stability of the road. A relatively shallow depth, ranging from 3.7 m to 4.29 m, was the depth to the water table of the four wells close to the road. Therefore, the possible causes of pavement failure are the thick and low resistive layer, the near-surface linear features suspected to be fractures/faults, and the water table’s shallow depth.

Geophysical research on the IGAN Glacier in 2021

The results of radar studies of the IGAN glacier carried out in 2019 and 2021 are presented in the paper. Measurements of the thickness of the snow cover and ice were carried out using the PICOR-LED GPR (1600 MHz) and VIRL-7 (20 MHz), respectively. Studies have revealed significant winter snow accumulation on the glacier and its stable spatial distribution, and also showed a significant ice thickness (up to 106 m) and the polythermal structure of the glacier. Electrotomography was used to monitor the central part of the glacial moraine. Two-dimensional geoelectric sections and a three-dimensional geoelectric model of the internal structure of the moraine are constructed. The size of the rock-ice core (high-resistance rocks) increases towards the center of the moraine, nevertheless, there is an active degradation of frozen material in the marginal parts of the moraine.

Groundwater exploration using vertical electrical sounding techniques in parts of Etche Local Government Area of Rivers State, Nigeria

Vertical Electrical Sounding (VES) was carried out in parts of Etche Local Government Area, Rivers State, Nigeria to investigate availability of groundwater. An ABEM SAS 1000 terrameter was used. Schlumberger configuration was adopted for the sounding to acquire a 4 point data, with the use of ID Interpex software in order to know the subsurface variations in resistivity with respect to depth. The investigation revealed the subsurface, thickness of lithology, prolific aquiferous zones, the resistivity curve portrays an overall increase in resistivity trend ranging from 228.7Ωm - 5872Ωm. The resistivity trend in the form of ρ1< ρ2< ρ3< ρ4< ρ5, indicates the presence of conductive materials present at a shallow depth of the point of survey. The highest resistivity value is observed in the fifth layer and it is believed to have gravely sized particles. A stratigraphic layer with gravely sized particles in this area revealed a good aquifer quality with reasonable quantity of aquifer fluid contained within the interconnected pore spaces. This zone of the studied area contains rock units from the geoelectric section such as silt, medium sand, coarse sand and gravel. The fifth layer is the prospect zone for aquifer delineation. A geoelectric section drawn from the resistivity data shows that the first layer is silt, the second layer is fine sand, the third layer is medium sand, the fourth layer is silty sand, the fifth layer is fine sand and the sixth layer is medium sand. The sixth layer is believed to be the prospect zone for aquifer characterization. A suitable data from drilled boreholes should be introduced to this study so as to have a profound knowledge and views about the grain size, sphericity, roundness and parking. These characteristics will be useful to determine the dominant grain size existing in these aquifers and characterize them appropriately.

Groundwater Exploration Using Vertical Electrical Sounding And 2D Electrical Resistivity Tomography In Shale Formation: A Case Study Of Sabongida, Plateau State, North Central Nigeria

Sabongida is characterized by lots of abortive boreholes which are often shallow as a result of the complex nature of shale formation in the area and limited application of integrated geophysical techniques before drilling of boreholes. The presence of shale formation in the area makes it extremely difficult to drill productive boreholes, while the existing hand dug wells are always shallow due to the difficulty in digging deeper wells, this and other factors motivated the choice of the study location for the purpose of proffering solutions to solve the perennial water problem in the area. Twenty-two (22) vertical electric soundings data (VES) using Schlumberger array with the aid of Ohms mega resistivity meter were conducted with electrode spread of AB/2 = 215 m and eleven (11) 2D electrical resistivity tomography data (ERT) using ADMT – 600 S - X equipment were acquired. ERT was conducted using 20 m as the length of each profile with 300 m in 10 profile lines and 400 m as the depth of probing. The result of the VES interpretation shows three to five geo-electric layers while the geo-electric section revealed the aquifers to consist of sandstones with varying thicknesses. Two groundwater potential zones were delineated as shelly sandstones and clayey sand. The different color band indicates the different layers within the ground as the soil resistivity varies, blue indicates low resistivity values, green - yellow indicates moderate resistivity values while high resistivity values are brown - red. The results from the 2D images indicate the low resistivity regions, suggesting aquifer is within the depths of 150 to 300 m. Thus, the recommended depths for drilling of productive boreholes are 180 to 210 m and 270 to 300 m in Sabongida.

Assessment of Hydrocarbon Pollution in Groundwater Using Electrical Resistivity Method

Hydrocarbon contamination of the groundwater system is a problem facing residents of Ejigbo, Lagos, Southwestern Nigeria. The area hosts the busiest satellite petroleum depots in Nigeria, and residents have attributed pollution of the groundwater system to hydrocarbon spills from possible pipeline leakages. This study aimed to identify and characterize the source and extent of the groundwater system contamination in the study area. The electrical resistivity method was adopted, comprising 2D Electrical resistivity imaging (ERI) and Vertical Electric Sounding (VES) techniques. Data acquired were processed and analyzed to obtain geoelectric sections, longitudinal conductance map and 2D ERI sections for the study area. Three distinct geoelectric zones were delineated, with the intermediate zone identified as the contaminated shallow aquiferous unit. This unit's resistivity values ranged from about 400 - 5000 ohm-m at a depth of 5 - 35 m. On the 2D ERI sections, possible locations of pipeline leakages were identified. On some ERI sections, a linear feature with resistivity value less than 300 ohm-m was observed from the surface down the depth of the entire section, truncating the horizontal flow of the contaminated unit. Generally, the results indicate that the contamination of the shallow aquifer in the area is widespread and mitigation measures should be urgently undertaken.

Determination of the saline water intrusion zone and its contamination with ground water in the Dibddiba aquifer using vertical electrical sounding technique at Basrah Governorate, southern Iraq

Thirty Vertical Electrical Sounding (VES) measuring points (Schlumberger array) were carried out in order to determine the number of the underlying layers, depths and their thicknesses, as well as ground water table and its influence by the saline water coming from the sea or even underlying layer. These points were distributed within five profiles, 500 m spacing between points. The length of each profile is 3 km and the distance between profiles is 2 km. These points were chosen at Basrah Governorate, southern Al-Zubair district. Qualitative interpretation was applied to study the type of the electrical field curves, which were classified to HKQQ, KQQ, KQQQ, QQQ and QQ. Five apparent resistivity sections and eight isoresistivity contour maps were drawn. Quantitative interpretation was carried out using five geoelectrical sections which were drawn along the selected profiles. Number of the underlying layers, depths, thicknesses and depth of ground water table were determined for each VES point along the investigated profiles. Also, decreasing of the apparent resistivity values with depth was noticed especially at the groundwater bearing intervals. This is because of the increasing of salinity in ground water at these intervals especially at the mid-way of all considered profiles. The rise of saline water belong to the lower part of the Dibddiba aquifer towards the brackish or fresh water existed in the upper profile due to the unprogramm able pumping processes which may cause mixture between them and make the resultant water more saline. Large reduction in the apparent resistivity values was also observed at the eastern parts of the study area near Khor Al-Zubair boundaries which indicate high electrical conductivity values. This is led to the increasing of saline water that probably comes from the sea. This fact is certainly approved by the interpretation of the is oresistivity contour map plotted for the upper part of aquifer and by comparing hydrochemical analysis for ten wells with the above result.

Geological and Hydrogeophysical Investigation of Angwan Zakara, Keffi Sheet 208N.E of North Central Nigeria

The geological and hydrogeophysical assessment of the groundwater prospect/potential in Angwan Zakara and its environs, Karu Local Government, Nasarawa State, North-Central, Nigeria has been carried out in this study. The study area covers 25km2.The area is underlain by the Basement Complex of the North-Central Nigeria consisting of Medium grained biotite granite, biotite gneiss, phyllite and un-mappable muscovite schist with structural features such as joints, veins, foliation, faults, and xenoliths trending NW-SE direction. Forty Nine (49) Vertical Electrical Sounding were carried out in the study area using Omega Resistivity Terrameter, GPS12 Garmix with a maximum cable spread of AB/2=100m and MN/2=5m. The results obtained from the field data were interpreted using IXID Software for quantitative analysis. True resistivity map, piezometric map, basement resistivity map and depth to basement map were prepared and interpreted using computer software for qualitative analysis (SURFER 8). From the IXID interpreted results, five (5) curve types were obtained from the acquired data namely A, H, KH, AH, and HK curve types are the dominant. The study area showed depth to basement ranges from 20-90m. That revealed good groundwater potential. The study area revealed 4-7 lithologic sequences consisting of top soil, laterite, clay, weathered/ fractured basement however the host rocks in the study area are biotite granite, quartzite and schistose-gneiss. The results obtained shows that the direction of water flows revealed five ridges R1-R5 and four depressions D1-D4 with receptacles trends of the ridges are R1 and R2:NW-SE; R3 N-S, R4 : NE-SW and R5; E-W. The geoelectric sections were produced and correlated with the geology of the study area and it was found to be in conformity with the each other. Based on this, the study area is zoned into three namely good, moderate and poor groundwater potential zones.

An integrated approach for the identification of potential shallow groundwater zones in west-central Saudi Arabia

This study aimed to identify groundwater resources at Harrat Khaybar to meet the increasing demand for groundwater for drinking and other purposes, including agricultural and industrial activities. Aquifers were assigned based on integrated electrical resistivity tomography (ERT) and hydrogeological data. Twenty-three ERT profiles ranging 590–890 m long distributed across Harrat Khaybar were acquired. The ERT data were processed to obtain 2D subsurface geoelectrical sections that indicated a variable depth for groundwater as 6–280 m. To investigate water quality, 69 groundwater samples were collected from intensively pumped wells distributed throughout the Harrat. The depth to groundwater measured in these wells ranged 1.5–80 m. It was concluded that Harrat Khaybar is composed of basaltic lava flows underlain by alluvial deposits, which represent two significant water-bearing formations: sub-basaltic alluvial deposits and basalt flows. The depth to the groundwater abruptly deepened from 1.5 to 80 m in the northeast and southwest directions, which could be due to groundwater-bearing formations dipping in these directions or northwest-orientated tension faults. The groundwater quality was assessed in terms of total dissolved solids (TDS), which ranged from 225 to 8340 mg/l, and a TDS-drilling zone encountered in the western part of the Harrat, the following similar most likely resulted from groundwater mineralization. The concentration of TDS generally decreased toward the east in the groundwater flow direction. The pH (6.5–8.1) of the samples indicated that the groundwater pH meets quality standards for domestic and irrigation purposes. It is concluded that, the application of both methods will be of great benefit to identify the groundwater sources and its quality as well.

Hydrogeological mapping from Landsat 8, SRTM images, vertical electrical soundings and hydraulic parameters of aquifers: Case study of the South Western part of Baleng Watershed

The main aim of this study is to carry out a hydrogeological assessment to reveal suitable sites for the implantation of hydraulic structures like water boreholes. Petrographic studies put into place granitic rocks with numerous biotite in the Northern part of the map and basaltic rocks with phenocryst of olivine in the South. Lineaments extracted from satellite images revealed two major trends of N50–60°E and N70–80°E. A total of sixty-four Vertical Electrical Sounding (VES) data were acquired using Schlumberger configuration array, 2-D sections and hydraulic parameters of aquifers were deduced. The geoelectric sections characterize the subsurface into four geoelectric layers namely: topsoil with (resistivity values lower than 300 Ω m), weathered basement with (resistivity values ranging between 300 and 600 Ω m), fractured basement (resistivity ranging between 600 and 800 Ω m) and a more or less fresh bed rock with resistivity value up to 4000 Ω m. The hydraulic assessment of aquifers revealed a high conductivity value of 34 m/day, porosity of 41% and a high transmissivity of 429 m2/day indicating a highly interconnected fractured basement of the study area. Groundwater potential map revealed Toungang, Lafé and Ndionkou villages as suitable sites for water boreholes implantation with an average aquifers roof depth ranging between 1to 31 m.

Geoelectric studies of the Kozloduy nuclear power plant region, Bulgaria

The task of the work was geoelectrical studies using variations of the magnetotelluric (MT) field of the Kozloduy nuclear power plant (KNPP) region and the integration of its results with other geological and geophysical knowledge. This paper presents the determined interpretation parameters of the MT field. The KNPP is located on the right bank of the Danube River in close proximity to the river. This fact, together with the location of electrified railways determined the unique network of locations of observation points for MT field variations. Based on the analysis of Earthquake Catalogs of Bulgaria and international seismicity databases, a map of the seismicity of nuclear power plant areas was built. Over the past 50 years, about 750 earthquakes (mainly south of KNPP) have been recorded at a distance of 40—80 km from the KNPP. Two magnetotelluric stations GEOMAG-02 were used at measurement sites, but equipment for recording electrical channels was available only for one station (due to the lack of another set of non-polarizable electrodes). The MT field variations were observed at 21 points, which are located on the territory with sides approximately 30—35 km from east to west and 40—50 km from north to south. For all observation points on the profile, only the parameters of the vertical magnetic transfer function (VMPF) were determined, in the form of the real (Cu) and imaginary (Cv) parts of the induction vector. The steadily induction vector was defined for periods from 10—20 to 4900—10 800 s. For most points it was possible to estimate the values Cu, Cv with an error of 0.02—0.04 and AzCu, AzCv 3—5°. The analysis showed the presence of anomalous behavior of Cu, Cv in different intervals of periods at some points. In the shortest (about 20 s) and longest periods (600 to 1000 s), the Cu directions completely coincide and indicate the presence of anomalous conductivity of the quasi-longitudinal strike to the west of the study area. This behavior of the Cu vector is in good agreement with power isohypsum strike of the Cenozoic deposits. At intermediate periods of 50—200 s, the behavior of Cu is more complex. Approaching the zone of high seismicity, the direction of the Cu differs from the previous ones by almost 90°. On the Geoelectrical sections, obtained as a result of 1D inversions of MTS curves at 4 points located in the southern part of the region, anomalous layers are identified (ρ about 10 ohm · m, the depth of the center of the object is 15—20 km). It can be assumed that well-conducting objects in the Earth’s crust of the region, apparently, prevent the propagation of seismic waves from nearby earthquakes to the north towards the KNPP.

Comparison of Soil Pollution Due To E-Waste Pollutants at Two Dumpsites in Lagos State Using the Geophysical Assessment Method

Soil degradation forms a part of the significant impacts arising from indiscriminate disposal of e-waste. This study was aimed at assessing, through the analysis of VES and 2D-Wenner array configuration data, not only the magnitude of legacy contamination by e-waste in terms of depth and spread but the level of impact as a result of the soil type or nature. The results of the VES data and 2D resistivity analysis showed that Alaba dumpsite was highly impacted by the e-waste due to the permeable geoelectric characteristics of the lithologic units beneath the dumpsite while Soulous- Igando recorded relatively high resistivity values which correspond to the clay column identified in the geoelectric sections of the site, thus the level of soil impact was low because, the clay/laterite column of the subsurface of Soulous-Igando site provides a means of preventing leachate movement down to the aquifer. The sites might need to be recovered in the future for a better developmental project; hence, the benefits of this research on the appropriate methods to detoxify the sites. In addition, the results from this study could facilitate Lagos State Government decisions on improving protection for groundwater resources for residents around the study area.

Aplikasi Geofisika Terpadu Untuk Penelitian Potensi Air Tanah Aquifer Batu Pasir Di Alasombo, Indonesia

The purpose of this study was to determine the potential of groundwater in Alasombo, Weru District, Sukoharjo Regency, Indonesia. The investigation has been carried out using geophysical methods that are integrated with surface geological data to obtain an interpretation of the hydrogeological control of the aquifer. The lithology of the aquifer is dominated by sandstone which controls its role as 2 types of aquifers, namely unconfined aquifers or free aquifers and semi-confined aquifers or semi-free aquifers. The geoelectrical section shows that the groundwater-carrying layer that functions as an aquifer is the sandstone layer in the second layer and sandstone in the base layer. As an artesian aquifer or a confined aquifer, sandstone aquifers have a water volume between 31.5 to 260 m3/day, in a northwest-southeast direction. In terms of the quality of the conductivity value of water in the field, below 1500 µs/cm is freshwater type groundwater that can be recommended as a source of clean water.