Geoelectrical Profiles Research Articles

A hydrogeophysical conceptual model in the exploration of the "Las Sierras" aquifer: Case of Subwatershed III, southeast sector of Lake Managua, Nicaragua

This study proposes a hydrogeophysical conceptual model in a region southeast of Sub-basin III, which is part of the "Las Sierras" aquifer. The methodology employed combines geological data obtained from wells with geo-electric profiles, thus allowing a more precise representation of an underground valley hitherto unknown, primarily related to the materials of the Middle Las Sierras Group (TQps-M), identified as the main aquifer in the area. The delineation of hydrogeological units was carried out considering geological and geophysical conditions, providing valuable information to understand the distribution and behavior of groundwater in the region. The precise identification and delineation of hydrogeological units enable better management of groundwater resources in the region. This more detailed knowledge enables more effective strategies for the preservation and sustainability of local aquifers.

Geoelectrical and seismoelectric mapping of subsurface pollution in a closed landfill near the Tongo Bassa and Ngongue river, Douala Cameroon

Located in Douala V (Cameroon), Makepé Missoké is a lowland area that is influenced by the Tongo Bassa and Ngongué rivers. The site has a closed dumpsite, that operated from the 1975’s to 2003 for the disposal and storage of domestic waste produced in Douala. Geoelectric profiling (ERT) coupled with seismo-electric imaging was used to characterize the shallow aquifer of the Douala subbasin and map subsurface pollution. Fourteen geoelectrical profiles were deployed between June and August 2018 and March 2019. Along these lines, 49 sets of seismo-electric point data were collected in December 2021. A total of 118 wells drilled (2018) were used to obtain water level and topographic data. The aquifer geometry, hydraulic characteristics, permeability, lithology and leachate plume extent were determined. This survey enables us to visualize waste infiltration and migration within Makepé. The drilled wells indicate that the main lithologies observed are clay, sandy clay, sand, clayey sand and gravel. The leachate plume observed after processing the electric profiles had a resistivity signature of ≤ 10 Ωm, and high electrical conductivity are observed in some wells. The leachate migrates within the subsurface along a northwest‒southwest trend, where ground water pollution is observed due to leachate infiltration. This infiltration resulted in poor water quality indices in some collected samples. Such pollution is common in unconfined aquifers (< 50 m) due to the absence of a confining layer at the landfill. An increase in resistivity values with depth toward the northeast direction indicates progressive vertical dilution during leachate mineralization. This study integrated geoelectric and seismo-electric tomography with basic water chemistry analysis to effectively characterize the groundwater within the phreatic Quaternary/Mio-Pliocene aquifers of the Douala basin.

Hydrogeophysical characterization of the Bir Guendouz basin (SW Morocco): Insights into its relations to the Senegal-Mauritanian basin

The Senegal-Mauritanian Basin onshore is the largest among the northwest African Atlantic margin basins, covering approximately 350,000 km2 and extending from Morocco to Guinea Bissau. Although valuable information is provided on the Senegalese part, data on other parts of the basin are scarce. The study aims to visualise the subsurface structure and describe the distribution patterns of Meso-Cenozoic deposits in the Moroccan portion of the Senegalo-Mauritania basin. The dataset integrates information from 750 vertical electrical soundings, hydrogeological drilling data, and wireline logging into a Geographic Information System (GIS) platform and 3D modelling software. A new three-dimensional model has been created to represent the topmost layer of the Palaeozoic substratum. Additionally, thickness maps and geo-electric profiles have been developed for distinct geo-electric intervals, including the lower, middle, upper, and surface layers. The study presents the geometric properties of two aquifers, namely, the ''upper and lower'': the Continental Terminal sandy and sandstones, dating back to the upper Miocene to Pliocene period, and the Paleocene sand to shaly sand. The upper aquifer has a thickness of 20 m in the eastern region, whereas it thickens to nearly 100 m towards the west, approaching the coastline. Similarly, the lower aquifer's thickness ranges from 100 m to 400 m in the same direction. The resistivity values range from 5 to 240 Ω m, providing an average of 120 Ω m. Four discontinuities have been identified in the sections, which may indicate lateral facies modifications or synsedimentary faults, correlating with Atlantic margin structuration and Meso-Cenozoic sea-level variations. The parameters' range for various mappings, models, and quantitative descriptions of reservoir properties. The new structural and hydro-stratigraphic model provides novel insights for researching this critical area.

Interpretation of vertical electrical soundings by means of ISM, PHT and C-N, case of a ditch in Al-Sharquieh phosphate mine in Syria

The main objective of this paper is basically to calibrate and compare the different geoelectrical results obtained by the three interpretative techniques of the inverse slope method (ISM), Pichgin and Habibuleav (PHT) and concentration-number (C-N) fractal modeling with the well lithology of an existing known ditch in the Al-Sharquieh phosphate mine in Syria. Those interpretative techniques are applied herein to interpret the vertical electrical soundings (VES) points measured along a parallel profile to the ditch. ISM reveals the presence of four to five geoelectrical layers in the study region. The PHT allows the determination of the tectonic subsurface features of the study region, by analyzing the non homogeneity points and their distributions along a given geoelectrical profile. The fractal C-N modeling provides the different apparent resistivity ranges dominating in the study region. Good agreements are obtained between the direct observed field lithological descriptions of both wall sides of this ditch, and the results obtained by those three interpretative geoelectrical techniques. The high radioactive readings exceeding four hundred count per second (cps) are due to the presence of secondary uranium accompanied with fractures, cracks and joints. The secondary uranium occurrences accompanied by phosphate deposits are found in the study area in the fractured zones, as determined by the geoelectrical PHT technique. The three mentioned geoelectrical methodologies are therefore used as indirect techniques for delineating the radioactive zones related to uranium prospecting. It is a successful application of the joint use of those three techniques, that could be applied in mining to delimit the subsurface geological structure. The reliability and efficacy of (ISM), (PHT), and (C-N) fractal modeling techniques are consequently well confirmed, and it is therefore recommended to use and apply them for characterizing and describing similar lithological phosphatic sequences, and for several shallow mining, environmental and civil engineering applications.

Holocene landscape reconstruction in the surroundings of the Temple of Pepi I at ancient Bubastis, southeastern Nile Delta (Egypt)

AbstractIn ancient Egypt, lakes, canals, and other water bodies were an essential part of the sacred landscape in which temples were embedded. In recent years, geoarchaeological research at the site of the Temple of Bastet at Bubastis in the southeastern Nile Delta has proven the existence of two water canals surrounding the temple. It has now been investigated whether these canals were connected to the Temple of Pepi I (2300–2250 B.C.E.), located approximately 100 m to the west of the Temple of Bastet. To explore the Holocene landscape genesis of the Temple of Pepi I, 15 drillings and six geoelectrical profile lines were performed in the surroundings of the temple in spring 2022. The results show loamy to clayey sediments in deeper sections of all drillings with a maximum thickness of 1.70 m, indicating a marshy or swampy depositional environment. Based on the recovered sediment sequences and archaeological remains in the vicinity of the Temple of Pepi I, the marshy or swampy area existed before the Fourth Dynasty. During the Old Kingdom (ca. 2850–2180 B.C.E.), the former marshland either dried up through natural processes or was intentionally drained and filled with sediments for subsequent use for occupation. Regarding the original research question, there is as yet no evidence for a direct connection to the canals of the Temple of Bastet.

Underground-caves connectedness preview using the geoelectrical profiling method as an effort to revive natural tourism in “Gua Pandan,” East Lampung Regency

The Covid-19 pandemic has made one of the tourists in the East Lampung regency inactive, namely “Gua Pandan.” Due to its unique location geologically, efforts must be made to revive the area. One of the approaches is applying an indirect method, namely the geophysical method. One of them is the geoelectrical profiling method. Six lines are spread in the study area with a length of 70-105 m. The target is a cave filled with air because it is suitable as a tourist spot. Based on the measurement results, a very high resistivity value of more than 5,000 Ωm is suspected to be an air-filled cave. The cave area that is probably safe is about 120 m long with 1-3 m depth below the ground surface, 2-8 m width, and 2-6 m height. However, a safety assessment is necessary for feasibility so that the cave is worthy of being re-activated as a tourist spot.

Near-Surface Geophysical Characterization of Lithologies in Corfu and Lefkada Towns (Ionian Islands, Greece)

Lefkada and Corfu old towns are located in the western part of Greece, in the Ionian Sea. Their proximity to the Hellenic subduction zone (HSZ) is the reason for their intense seismicity. The main goal of this study was the estimation of the geotechnical characteristics of the subsurface, with the contribution of applied geophysical techniques. Therefore, seismic refraction tomography (SRT) and multichannel analysis of surface waves (MASW) were applied. A total of thirty-three (33) seismic and geoelectrical profiles were performed in both towns in order to evaluate the geotechnical characteristics of the subsurface formations. Additionally, subsurface resistivity distributions were investigated with the application of electrical resistivity tomography (ERT). Some important elastic moduli were calculated through the combination of estimated seismic wave velocities and laboratory density measurements. The horizontal distribution of seismic velocities and mechanical properties (σ, E, K, G) of Corfu town was illustrated in maps, for the depth of 5 m. The geophysical interpretation also revealed that Lefkada’s subsurface consists of only one compact geological formation, with little or no variation of its geophysical-geotechnical characteristics. Beyond that, the ground type classifications for the two towns were determined according to the European Committee for Standardization Eurocode 8, based on VS30 values.

Time-Domain Electromagnetics as a Geophysical Tool in Hydrogeological Exploitation Projects in Mesozoic Formations

The need to use groundwater resources for agricultural and livestock farms is a constantly growing issue, as these resources condition the socio-economic development of many areas with limited climatic regimes and surface water resources. Decisions on the location and characteristics of groundwater extraction works are based on hydrogeological studies, in which geophysical techniques are a very useful tool. In our study, the Time-Domain Electromagnetics technique (TDEM) was used, which significantly improves the precision and safety when planning to drill for water extraction in Mesozoic formations thanks to the significant resistivity contrast among its different hydrogeological units. The performance of a research campaign using TDEM allows for obtaining 2D geoelectrical profiles which define the hydrogeological structure of the study area and the materials of which it is composed, enabling the selection of a site where drilling can be carried out with the best prospects of success. This article shows the usefulness of this study methodology, applied to Mesozoic formations in a specific area located in the municipality of Liceras (Soria, Spain).

The Use of Multi-Geophysical Methods to Determine the Geothermal Potential: A Case Study from the Humenné Unit (The Eastern Slovak Basin)

The exploration of the geothermal potential of a geological unit has multiple aspects. The most important elements are the geological structure, the hydrogeological conditions, and heat flow. The analysis of the above-mentioned elements attempts to help maximize the use of a geothermal aquifer’s potential. When choosing the most appropriate geophysical method, it is important to consider various factors, such as basic structural parameters as well as the total cost of exploration. This is especially true for low-thermal areas. Comparison of multi-geophysical exploration methods used in the study of the carbonate aquifer of the Humenné Unit identified the advantages and weaknesses of each method. The Humenné Unit is the north basement unit of the Eastern Slovak Basin (with a heat flow value ranging from 100 to 125 mW·m−2), which is part of the Pannonian Basin (with a high heat flow ranging from 50 to 130 mW·m−2). The calculation of the geothermal potential was based on the results of several methods. Some important geophysical survey methods resulted in: (a) deep seismic cross-sections which clarified the position and overall internal structure of the aquifer (b) gravimetric measurements in the form of a map of the Complete Bouguer Anomalies (calculated for density 2.67 g·cm−3) which confirmed the presence of structural elevations and depressions. These elevations and depressions intensified the water yield, heat flow and raised the overall temperature (c) the use of geoelectric resistivity profiling, which is a fast and cheap method, but is limited by depth. The similar resistivities ρ: 80–360 Ωm of carbonates and andesites was a serious problem. The specific heat-energy potential has a wide range of 0.337–19.533 GJ/m2. The highest values above 15 GJ/m2 are reached in areas where the temperature on the surface of the Triassic carbonates exceeds 90 °C.

Performance of geophysical methods in determining fault zone at Darakeh Area (Tehran Province; Iran)

Darakeh area is one of the major areas in terms of seismic hazards in Tehran. The North Tehran Fault has gone through the center of the studied area, thus creating fractures, displacements and folds of layers, forming anticlines and synclines. Considering the old residential texture understanding the tectonic characteristics and locating the hidden faults of the region can be quite useful in providing thematic maps and preventing damages caused by potential earthquakes. Nevertheless, no geophysical studies have been carried out on this area so far. To map the area, three GPR and two electric resistivity profiles were designed based on the identified tectonic lineations and previous seismic studies on the area. Each GPR profile, was 100 m in length and surveyed using a MALA GPR with an unshielded 50-MHz antenna. The geo-electric profiles were surveyed by Wenner-Schlumberger array. The results of the processed profiles demonstrate a severe drop in resistivity in some regions which could be due to the presence of fault zones and potential cavities in the region under study.

Geological and structural characterizations of a basaltic environment by vertical electrical soundings and multifractal modeling techniques in Deir El-Adas Area, Yarmouk Basin, Syria

Concentration-number (C-N) fractal modeling technique is adapted and newly proposed to interpret vertical electrical sounding (VES) measurements. This proposed technique is practiced herein on a case study taken from Deir El-Adas, Southern Syria, where four VES geoelectrical profiles (Pro-1, Pro-2, Pro-3, and Pro-4) are interpreted. The general targeting concept of this technique is to use the threshold break points determined by the use of C-N log–log plots to indicate the passage from geoelectrical layer to another one. Different apparent resistivity population ranges are accordingly well determined for the treated geoelectrical data. Those apparent resistivity ranges are consequently used to establish 2D and 3D semi quantitative interpretations of the studied geoelectrical profiles for different fixed spacings AB/2. The established geoelectrical sections clarified the subsurface geological structures and contributed in distinguishing and classifying lateral and vertical different type of basaltic features in the study area. The fractal C-N model can be therefore used to calibrate the ID traditional inversion VES interpretation, particularly in basaltic environments, characterized by sharp and rapid resistivity variations. This calibration is one of the advantages of this fractal technique. This technique is therefore recommended to be applied in other similar basaltic environments.

Fan morphology evidence on Late Quaternary deformation in the southern front of the Central and Eastern Alborz Mountains in the Eyvanekey, Garmsar, Semnan areas, Northern Iran

Although numerous studies have been done on the Alborz Mountains, few have examined Quaternary events based on alluvial fans which are located in front of the southern limb of the Central and Eastern Alborz Mountains. This study analyzed the morphometric indexes for 131 alluvial fans (three generations) in the Eyvanekey, Garmsar, and Semnan areas (As, WLF, Bull, Fa, Fs, Fg, Fc, R) as well as for basins (Da, AF, T, Bs), mountain fronts (Fmf, Smf, Vf, Fd), and rivers (Sl). The morphometry results show that a young deformation in this area has caused on uplift in the crust along structures in the Alborz. The Garmsar area is more active than the Semnan area in which both are more active than the Eyvanekey area. All of the alluvial fan evolution in this area relate to the Quaternary events. The study on the information obtained from the exploitation wells and geoelectric profiles of the region shows that the Alborz uplift in the north is associated with the erosion and deposition of the new deposits in the form of alluvial fans. The bedrock behavior at the base of the fans has a direct effect on the formation of the second- and third-generation fans. The effect of the continual compressional tectonics in the Late Quaternary is associated with the uplifting evaporite masses, the uplifting hanging walls of the reverse faults, and the growth of the folded structures.

The Applicability of an Inverse Schlumberger Array for Near-Surface Targets in Shallow Water Environments

We investigate the applicability of offshore geoelectrical profiling in the littoral zone, e.g., for archaeological prospection, sediment classification and investigations on coastal ground water upwelling. We performed field measurements with a 20 m long multi-electrode streamer in inverse Schlumberger configuration, which we used to statistically evaluate measurement uncertainty and the reproducibility of offshore electric resistivity tomography. We compared floating and submerged electrodes, as well as stationary and towed measurements. We found out that apparent resistivity values can be determined with an accuracy of 1% to 5% (1σ) depending on the measurement setup under field conditions. Based on these values and focusing on typical meter-scale targets, we used synthetic resistivity models to theoretically investigate the tomographic resolution and depth penetration achievable near-beach underneath a column of brackish water of about 1 m depth. From the analysis, we conclude that offshore geoelectric sounding allows the mapping of archaeological stone settings. The material differentiation of low-porosity rock masses < 15% is critical. Submerged wooden objects show a significant resistivity contrast to sand and rocks. Distinguishing brine-saturated sandy sediments from cohesive silty-clayey sediments is difficult due to their equal or reversed resistivity contrasts. Submarine freshwater discharges in sandy aquifers can be localized well, though difficulties may occur if the seafloor encounters massive low-porosity rock masses. As to the measurement setups, submerged and floating electrodes differ in their spatial resolution. Whereas stone settings of 0.5 to 1 m can still be located with submerged electrodes within the uppermost 4 m underneath the seafloor, they have to be >2 m if floating electrodes are used. Therefore, we recommend using submerged electrodes, especially in archaeological prospection. Littoral geological and hydrogeological mapping is also feasible with floating electrodes in a more time-saving way.

Subsurface characterization of quaternary scarps and their possible connection to main structures of the western margin of Precordillera, San Juan, Argentina

The El Tigre fault provides a significant example of Pliocene-Quaternary tectonic activity at the West of Precordillera, receiving considerable attention in the last years. However, longitudinal thrusts of the nearest Sierra del Tigre and a minor piedmont deformation belt identified in its western piedmont are still poorly understood. The present work comprised a detailed map of the geomorphological features of tectonic origin and Quaternary alluvial fan terraces located between the Sierra del Tigre and the El Tigre fault. Several topographic and geoelectrical profiles across minor fault and fold scarps were surveyed to define the displacement scarps, the geological structure geometries at subsurface and their relationship with main structures. Geoelectrical models allowed us to recognize three geoelectrical levels: A (> 200–300 Ω.m) correlated to Pleistocene alluvial fan terraces Q4 and Q3; B (ranging from 50 to 300/450 Ω.m), under level A and correlated to the Neogene substratum (Rodeo Formation); C (< 30–40 Ω.m) intercalated in level B, conforming aquifers (20 and 40 m deep) within the Neogene substratum. Subvertical conductive zones (10–40 Ω.m) were correlated to high angle (~60°-80°) reverse faults, which are associated with open anticlines and synclines that affect the Quaternary levels and the Neogene substratum. The structural style interpreted here allows us to conclude that the main piedmont thrust is a frontal splay of the backthrust of the Sierra del Tigre with western vergence. A better connection to the compressive deformation component, which uplifts the range, instead of to the strike-slip deformation component of the El Tigre Fault is demonstrated. This tectonic propagation probably happens during Middle-Upper Pleistocene to Holocene. The observations show that minor deformation belt is subjected to piedmont compressive movements while the El Tigre Fault absorbs the strike-slip movements, so a local partition of the deformation in the western margin of Precordillera probably happens during Quaternary.

Volumetric characterisation of waste deposits generated during the production of fertiliser derived from phosphoric rock by using LiDAR and electrical resistivity tomography.

The lack of environmental regulations before 1998 brought about significant ecological consequences in Europe. There are 4,000,000 ha potentially contaminated by waste, resulting from industrial activity. These sites present abnormal values of salinity, alkalinity, and organic and inorganic pollutants. A representative example of this is the production of fertiliser derived from phosphoric rock through the wet acid process which mainly produces phosphogypsum and pyrite ashes. For each tonne of fertiliser produced, five tonnes of phosphogypsum are generated, which in most of the cases were simply piled into non-conditionate deposits; currently, there is no information about these deposits. Hence, fast and affordable methodologies should be developed to calculate the volume contained in the existing waste deposits. Thus, this study aims to: i) scan the industrial area selected in order to identify the distribution and possible variants of the waste that make up the configuration of geoelectrical profiles and boreholes, and ii) accurately determine the volume contained in the chosen deposits by merging Electrical Resistivity Tomography with LiDAR point cloud. Results show a range of deposit volumes that run from 4900 m3 to 59,300 m3. The density of LiDAR point cloud (1 point/m2) ensures metric precision for the superficial layer. The Electrical Resistivity Tomography revealed the geometry of the deposits that superposes two layers marking the border between waste and natural terrain, and the boreholes guarantee the exactness of the waste layer thickness. This synergistic combination of Electrical Resistivity Tomography with LiDAR point cloud yields an accurate method that we used to calculate the volume of waste present in the deposits.

Sulfur and Nitrogen Gases in the Vapor Streams from Ore Cyanidation Wastes at a Sharply Continental Climate, Western Siberia, Russia

The article presents the results of the study of the vapor streams from sulfide-containing tailings after gold mining by cyanidation (Ursk waste heaps, Kemerovo region, Russia). The gas survey of sulfur dioxide, dimethyl sulfide, dimethyl sulfoxide, carbon disulfide, and N-containing substances concentrations was carried out using a portable device GANK-4 on a series of profiles covering the waste heaps and the surrounding area with simultaneous measurement of temperatures in the air and soil. The concentration maps-schemes of the studied gases in the surface layer were constructed. The high positive correlation of gases between themselves is established, which indicates similar mechanisms of their formation. The electrical resistivity tomography determined the internal structure of the waste heap. Active “breathing” zones were identified in which the maximum fluctuations in the concentrations of sulfur, selenium, and nitrogen-containing compounds in the near-surface air layer were recorded. Such zones are marked with lower resistances in comparison with other areas on the geo-electric profiles. There is an inverse correlation between the resistivity of the tailings and its temperature and a direct correlation between the concentration of gas in the air and the temperature of the soil. High concentrations of CS2, the volatile gas compound of the second hazard class, were found in the concentrations that exceed 6–8 times the daily average norm. Further investigation of the mine tailings seasonal transformation with the production of toxic gases deserves special attention due to high environmental risks and poor knowledge of this problem. The oxidation of ore cyanidation wastes in summer and methylation in winter due to seasonal temperature fluctuation lead to production of gases of great concern including toxic СS2.

Integrating GIS-based and geophysical techniques for groundwater potential assessment in Halabja Said Sadiq sub-basin, Kurdistan, NE Iraq

Groundwater is an important resource in Halabja Said Sadiq sab-basin, Sulaymaniyah district for agricultural and other uses. Continuous dramatic extraction of groundwater from legal and illegal wells led to a severe decline in the water table for the last thirty years. The objectives of this study are to delineate the groundwater productivity zones by combining the geographic information system and geoelectrical survey, which serves to recognize the locations of good groundwater storage and recharge zones. The Halabja Said Sadiq sub-basin has been selected as a case study to delineate the groundwater productivity zones. Four geoelectrical resistivity profiles conducted with electrode spacing 10 m and the length of the profiles is equal to 710 m. Themes such as hydrogeology, land use/land cover, topography, drainage density, soil type, slope, lineaments and rainfall maps are created. The thematic maps made with GIS platform and appropriate weights put to the attributes taking into account the influence on the storage potential of groundwater. The results of geoelectrical profiles revealed that the aquifer thickness is 150 m. Three zones of groundwater potential delineated which are low, moderate and high and cover 33 %, 24 %, and 42 % of the total area respectively. Spatially, the highest zone is located along with the Quaternary deposits which characterized by high lineament density, low slop, and pediment deposition&#x0D; The output of the groundwater potential model is verified by testing the discharge rate of the existing 580 wells. The results are revealed that most of the high yield wells are located within the high groundwater potential zone. Results of such verifications proved that the groundwater productivity areas recognized by GIS (AHP) and geoelectrical techniques are dependable and practical.&#x0D; &#x0D; http://dx.doi.org/10.25130/tjps.24.2019.112

Integrating GIS-based and geophysical techniques for groundwater potential assessment in Halabja Said Sadiq sub-basin, Kurdistan, NE Iraq

Groundwater is an important resource in Halabja Said Sadiq sab-basin, Sulaymaniyah district for agricultural and other uses. Continuous dramatic extraction of groundwater from legal and illegal wells led to a severe decline in the water table for the last thirty years. The objectives of this study are to delineate the groundwater productivity zones by combining the geographic information system and geoelectrical survey, which serves to recognize the locations of good groundwater storage and recharge zones. The Halabja Said Sadiq sub-basin has been selected as a case study to delineate the groundwater productivity zones. Four geoelectrical resistivity profiles conducted with electrode spacing 10 m and the length of the profiles is equal to 710 m. Themes such as hydrogeology, land use/land cover, topography, drainage density, soil type, slope, lineaments and rainfall maps are created. The thematic maps made with GIS platform and appropriate weights put to the attributes taking into account the influence on the storage potential of groundwater. The results of geoelectrical profiles revealed that the aquifer thickness is 150 m. Three zones of groundwater potential delineated which are low, moderate and high and cover 33 %, 24 %, and 42 % of the total area respectively. Spatially, the highest zone is located along with the Quaternary deposits which characterized by high lineament density, low slop, and pediment deposition&#x0D; The output of the groundwater potential model is verified by testing the discharge rate of the existing 580 wells. The results are revealed that most of the high yield wells are located within the high groundwater potential zone. Results of such verifications proved that the groundwater productivity areas recognized by GIS (AHP) and geoelectrical techniques are dependable and practical.

Integration of the GPR and radio-impedance techniques in studies of the Baikal rift zone

R adio wave propagation techniques have been very rarely applied to investigate tectonic fault zones and geoelectric profiles of the Baikal rift zone. In our study, we used a combination of g round-penetrating radar (GPR) and radio impedance techniques in order to identify and investigate tectonic crustal fault zones in the study area. Using soundings in the super-long, long and ultra short radio wave ranges (from tens of KHz to few GHz ) , we detected the tectonic fault zones in t he seismically active Baikal rift zone , specifically in the Tunk a depression and the areas of South ern Baikal and Kotokel lake s. Faults and fault zones were identified from impedance variations and changes in the geoelectric profiles by analyzing the radio impedance profiles and soundings in the super-long and long radio wave ranges . The georadi o location of fault structures in the ultra-short wave range made it possible to differentiate the patterns of tectonic disturbances up to individual seismic dislocations in sedimentary and crystalline rocks and to determine the kinematics of movements in the fault zone s . The techniques used in this study complement each other and ensure obtaining adequate quantitative descri ptions of the study object s . By i ntegrati ng various techniques of radio wave diagnostics , it is possible to obtain more detailed information on the structure s of the tectonic fault zones . The results obtained in this study and the radio impedance and GPR sounding and profiling techniques developed to investigate a heterogeneous underlying medium can be used in seismological and geological engineering surveys of the eastern and northern regions of Russia.

Assessment groundwater occurrences using VES/TEM techniques at North Galala plateau, NW Gulf of Suez, Egypt

Water resources assessment is important for urbanization and industrial projects in remote areas. As the area is far from the Nile and characterized by rarity of rainfall, the main source of freshwater is groundwater. Vertical Electrical Sounding (VES) and Time Domain Electromagnetic (TEM) methods are chosen. To overcome the ambiguity, TEM station no.1 was conducted close to a borehole. The information from the borehole includes lithology and producing aquifer zones. The processing started with the inversion of VES data then use the models obtained as the primary model for TEM inversion. The last models from VES and TEM were further used to construct 3 geoelectrical profiles and 8 contour maps illustrating subsurface water-bearing aquifers electric resistivity. From the results, two aquifers are found divided by a highly conductive clay unit. The shallow one is consisting of coarse sand with silt. It displays moderate to low resistivity, depth ranging from 6 m to 33 m underground surface and a thickness of 15–35m. On the other hand, the deep one shows low resistivity values that may show brackish to fresh water with depths to the upper surface ranges from 58m to 118m and thickness distribution of 26–80m. In general, the groundwater flow is expected to be from southwest to northeast towards Suez Gulf as indicated by the elevation trending of the aquifers. According to the resistivity distribution, the direction of seawater intrusion is the northeast in the directions of Suez Gulf.