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Vertical electrical sounding for revealing the groundwater resources in the geothermal spring of Jaboi volcano

Yanis Muhammad, Zaini Nasrullah, Abdullah Faisal, Isa Muhammad, Marwan Marwan, Idris Syafrizal, Paembonan Andri Yadi, Ananda Riski, Zainal Muzakir, Ghani Azman Abdul, Saputra Deni

Acta Geophysica

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2024

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Vol. 72, no. 3

1617--1635

EN

Geothermal energy is considered renewable energy that is environmentally friendly and sustainable compared to the conventional energy from fossil fuels. However, uncontrolled geothermal exploitation can cause a decrease in the groundwater table and reservoir temperature, such as in the Jaboi volcano on Weh Island, where a power plant has been built to generate electrical energy with an estimated power of 50 MWe but still has not been operated. A geophysical survey is needed to determine the local hydrothermal system, including groundwater reserves under the surface which can be used to refill the hydrothermal wells during exploitation. This study measured vertical electrical sounding (VES) data at 15 points near the crater and geothermal power plant. In addition, very-low-frequency (VLF) data that pass through the crater were also collected to determine the presence of other hydrothermal resources such as fractures and faults. The results of the 1D least-square inversion show three subsurface models where groundwater resources with low resistivity (< 1.5 Qm) are found at a depth of 50-100 m. The same results are also obtained from the 2D cross-section model that impermeable resistive anomalies in alluvial and tuff rocks dominate the near-surface area. The layer after groundwater is an impermeable rock in the form of breccia. The results of 2D VES and VLF modeling also show the presence of the Ceunohot and Leumomate faults, which are beneficial as fluid access to the surface. Based on the data analysis, the combination of VES and VLF data can be used to image shallow hydrothermal systems such as groundwater resources and faults in the Jaboi volcano.

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Parametric characterization, protectivity and potentiality of shallow hydrogeological units of a medium-sized housing estate, Shelter Afrique, Akwa Ibom State, Southern Nigeria

Ekanem Kufre Richard, George Nyakno Jimmy, Ekanem Aniekan Martin

Acta Geophysica

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2022

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Vol. 70, no 2

879--895

EN

Geoelectrical resistivity technology (GRT) constrained by geological information was used to map the hydrokinetic properties, as well as the protectivity and potentiality of groundwater system in a medium-sized and sort after housing estate in Southern Nigeria. The GRT deployed involved Schlumberger 1-D vertical electrical resistivity sounding (VES) and 2-D electrical resistivity tomography (ERT). The primary and secondary geoelectric indices were used in tandem with existing geological information to estimate the hydrodynamic parameter maps of the shallowest aquifer unit, maximally exploited in the area for optimal management of the unconfined aquifer system beneath. Total porosity (0.282–0.691), specific yield (0.040–0.107), field capacity/specific retention (0.242–0.623) and storage-dependent drainability efficiency (SDE) (7.6– 40.5%) were determined to depict the saturation dynamics in the study area. Results showed that the area has optimal release of pore water when the storage-dependent drainability efficiency is greater than 21%. The ensemble of potential index parameters such as transmissivity (57.4–4339.2 m2 /day), transverse resistance/aquifer potential scale (453.6–152,756.5 Ωm2), permeability (91.7–7269.7 mD) and hydraulic conductivity (57.4–4339.2 m/day) showed optimal potentiality but poor to moderate protectivity as evidenced by longitudinal conductance index (0.004–0.6218 Siemens). As many individuals have strong affinities to live in this fast, newly developed and competitive housing estate, it is a healthy practice that efficiently managed waste disposal arrangements/measures be put in place in order to ward of the exposure of leachates and other organic/inorganic wastes from permeating/draining into the already naturally vulnerable underlying hydrogeological units, where groundwater extracted for diverse use is stored.

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Speculation on the resilience of karst aquifers using geophysical and GIS based approaches (a case study of Iran)

Nassery Hamid Reza, Zeydalinejad Nejat, Alijani Farshad

Acta Geophysica

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2021

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Vol. 69, no. 6

2393--2415

EN

Employing the "resilience" term to groundwater is a formidable challenge. The situation is even more intricate for the karst aquifers which may act as surface water with low resilience, alluvial groundwater with high resilience, and a combination of both. The objective of this study is to assess the groundwater resilience and hydrogeophysical characteristics of Asmari and Ilam-Sarvak formations at Susan karst, south-west Iran. Hence, 260 vertical electrical soundings (VESs) were carried out with the Schlumberger array. The VES curves were interpreted, scored, and interpolated to produce a groundwater potential map. Moreover, a geographic information system (GIS)-based approach was employed, including six layers, i.e. distance to springs, elevation difference from springs, slope, lithology, fracture density, and fracture length density. The GIS criterial maps were generated, reclassified, weighted, and overlaid, such that a supplementary groundwater potential map was produced. The electrical resistivity values and degrees of smoothness of the VES curves depicted considerable groundwater potential for the Asmari formation. However, the groundwater potential of the Ilam-Sarvak formation may be attributed to the superficial fractured zones. On the other hand, the geospatial technology which is based on the surface indices represented enormous groundwater potential for both formations, especially for the Ilam-Sarvak formation. Finally, regarding the groundwater resilience, various hydrological characteristics occur for two karst formations in a small-scale region. The Ilam-Sarvak formation primarily behaves like the surface water with low resilience (conduit flow, low storage), and the Asmari formation portrays the features of the alluvial aquifers with high resilience (diffuse flow, large storage).

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Assessing the efects of 1D assumption violation in vertical electrical sounding (VES) data processing and interpretation

Mashhadi Seyyed Reza, Ramazi Hamidreza, Asgarpour Shahreza Mohammad

Acta Geophysica

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2020

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Vol. 68, no. 1

105--122

EN

This research aimed to discover the possible efects of 1D assumption violations on VES data interpretations. In order to do so, 1D inversion results of logarithmically spaced and linearly spaced VES measurements are compared with their relevant 2D inverted models. Some real case studies are also examined by 1D and 2D inversions to test the results. It is found that linearly spaced VES measurements are not really suitable for 1D inversion in the case of 1D assumption violations and logarithmically spaced VES can better handle these problematic features. In the case of semi-infnite horizontal layers and also small surface resistivity inhomogeneities, logarithmically spaced VES datasets mostly provide a reliable 1.5D model while linearly spaced VES datasets sufer from remarkable artifacts. In the case of vertical structures, both linearly spaced and logarithmically spaced VES techniques fail. In this case (i.e., a vertical dike), artifacts in the form of “extra layer” appear in those VES stations that are adjacent to the dike. However, for VES stations on the dike structure, no extra layer appears in the 1D inversion result. It must be emphasized that 1D violating features are not improbable in many geological situations so they must be considered in mind when processing and interpreting the geophysical VES data.

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Groundwater investigation through vertical electrical sounding at hilly area from Nooriabad toward Karachi

Soomro Asadullah, Qureshi Abdul Latif, Jamali Muhammad Afzal, Ashraf Arshad

Acta Geophysica

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2019

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Vol. 67, no. 1

247--261

EN

The study is conducted to focus on the subsurface geological and hydrological mapping for groundwater presence in the area located Nooriabad of the Jamshoro district left side of M-9 Motorway toward Karachi, Sindh, Pakistan. Vertical electrical sounding (VES) is carried out by using the Schlumberger electrode array method with ranging from 02 to 300 m. IPI2win software is used on the collected data of VES to interpret with qualitatively that indicated the four distinct lithological units demarcated as clay, sandy clay, shale and alluvium or weathered layer of Tiyon formation and limestone and fractured sandstone beds of the Laki formation of Eocene age. On the collected VES data, it is concluded that the first and second layer of soil is 16 m thick and composed of shale to clay beds and alluvium having the apparent resistivity between 05 and 15 Ωm. With increasing depth from 50 to 100 m, it is interpreted that there are fractured sandstone and limestone beds with average resistivity ranges between 15 to 60 Ωm. Further, processed the data and generated pseudo-section, apparent resistivity section and statistical curve by using software IPI2win to interpret the apparent resistivity map at 50, 60, 70 and 80 m are correlated with the hydrogeology and geology of the area. The results are interpreted that the good aquifer zones are present in the 50–100-m-thick limestone and fractured sandstone beds having interconnection with clay. Accumulation of groundwater is found by controlling the physiography and geological structure of the study area.

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Analiza możliwości zastosowania metody tomografii elektrooporowej (ERT) do rozpoznania miąższości pokrywy laterytowej

Pacanowski G., Czarniak P., Piechota A., Mieszkowski R.

Przegląd Geologiczny

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2016

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Vol. 64, nr 4

245--253

EN

The paper discusses the problem of determining the thickness of a laterite cover using electrical resistivity tomography (ERT) in a selected area of the Seram Island in Indonesia. Seram Island lies in the tropical zone between the Seram and Banda seas. The laterite covers are rich in nickel, cobalt, iron and other metals. Concentrations of these metals in the laterites are high enough to form economic deposits. A significant part of the report concerns the measurement technique (ERT method) in difficult climatic (high humidity and temperature) and topographic conditions (equatorial jungle with significant variations in elevation) and the methods of processing and interpretation of the acquired data. The problem seems very interesting, because geophysical prospecting is currently more and more often conducted in poorly accessible regions of the world. Additionally, there are no sufficient and commonly available publications that would allow us to get acquainted with local measurement problems by potential contractors of similar geophysical investigations. The primary result of the geophysical survey was to determine the electrical resistivity of bedrock and laterite. This was the basis for the development of sections of electrical resistive distribution for the ERT profiles, which enabled to estimate the depth to the crystalline basement and the laterite thickness. It also facilitated to produce a map of laterite thickness, which may be an important material to develop the concept of searching and mining of nickel and cobalt ore.

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Analiza porównawcza wyników badań geofizycznych i geologiczno inżynierskich na potrzeby ustalania modelu geologicznego – na przykładzie poligonu badawczego Kępa Włocławska

Gańko M., Mieszkowski R, Gańko A.

Przegląd Geologiczny

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2015

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Vol. 63, nr 2

121–-130

EN

The paper present the correlation of geophysical method with geological-engineering data. As an experimental testing ground, a terrain with simple soil conditions was selected, located on the W³oc³awek River-islet. This is a large alluvial area on the Vistula River, downstream of the W³oc³awek Dam. In the study, the following geophysical methods were applied: vertical electrical sounding (VES), refraction seismic, ground penetrating radar (GPR) and electrical resistivity tomography (ERT). The evaluation of geological-engineering conditions was executed by using the following methods: drilling, cone penetration test (CPT sounding), measurements of the underground water level and macroscopic and laboratory analyses of soils samples. The results obtained were described and presented in a graphic form.

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Rozpoznanie złoża piaskowców budowlanych z wykorzystaniem geofizycznych badań elektrooporowych i georadarowych

Klityński W., Stelmach K., Stefaniuk M., Karczewski J.

Przegląd Geologiczny

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2014

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Vol. 62, nr 10/2

621--628

EN

The paper presents the application of Vertical Electrical Sounding (VES) and Ground Penetrating Radar (GPR) into recognition of the geometry and vertical differentiation of a deposit of color sandstones that are commonly used as elevation stones in building industry. The investigations covered sandstones of Lower Cretaceous age (Albian) that occur at the foothills of the Che³mo Mt. near Kolonia Grabowie (Radomsko district, £ódŸ province). The former quarry of Grabowie is situated in the forest area of the landscape park and this blocked further exploitation from the documented deposit. On a limited scale sandstone is still quarried form the southern edge of the old quarry. However, poor recognition of the deposit hampers the effective exploitation. The objective of the geological investigations was to examine a new part of the deposit including identification of the roof and the bottom of sandstone complex, the thickness of overlying rocks, location of faults and weathered zones, as well as recognition of the lithology down to a depth of 8 m below ground surface. Resistivity distribution in the study area was assessed with the use of VES. Much higher resistivity of sandstones as compared to surrounding rocks was advantageous. Owing to high resolution GPR, the deposit boundaries could be delineated and the stratification within the sandstone complex could be represented. The investigations resulted in construction of 2D models of the deposit and surrounding rocks and gave information on the lithology.