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1

Self potential data inversion utilizing the Bat optimizing algorithm (BOA) with various application cases

Essa Khalid S., Diab Zein E., Mehanee Salah A.

Acta Geophysica

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2023

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Vol. 71, no. 2

567--586

EN

The Bat optimizing algorithm (BOA) is one of the metaheuristic algorithms and applied here to interpret self-potential (SP) data. The BOA is depending upon a bat echolocation behavior for global optimization, which the global optimum solution reached at the suggested minimum value of the objective function. The best interpretive source parameters for the subsurface structures occurred at the minimal the objective function value (global best solution). The BOA is applied to 2D SP anomaly data to estimate the characteristic source parameters (i.e., the depth to center, amplitude coefficient, origin location, geometric shape factor, and polarization and inclination angle of the causative buried structure). The BOA can be applied to single and multiple source structures in the restricted class of simple geometric shapes, which these bodies help in the validation of the subsurface ore and mineral targets. The stability and efficiency of the proposed BOA have been examined by several synthetic examples. In addition, three different real field examples from Germany and Indonesia have been successfully applied to ore and mineral investigation and geological structure studies. In general, the achieved results are in good agreement with the available borehole data and results mentioned in the literature.

2

Assessment of contamination in Namson Landfill, Hanoi, Vietnam by hydrogeophysical methods

Giang N. V., Vu N. T., Duan N. B.

Archives of Mining Sciences

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2018

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Vol. 63, no. 2

397--416

EN

The main objective of this study was to assess the environmental impact of the subsurface geological structure in Nam Son landfill by hydrogeophysical method. The Electrical Resistivity Tomography (ERT), Self-Potential (SP) and Very Low Frequency (VLF) method was used for geological structure investigation. Three profiles (total 900 m long) of two-dimensional ERT, VLF density sections and 180 SP data points scattered within the study area near the disposal site were implemented. Surface water and groundwater samples were collected from 10 sites in the area for hydrochemical analysis. Interpretations of geophysical data show a low resistivity zone (<15 Ω m), which appears to be a fully saturated zone with leachate from an open dumpsite. There is a good correlation between the geophysical investigations and the results of hydrochemical analysis.

PL

Podstawowym celem pracy było określenie stopnia oddziaływania na środowisko w podpowierzchniowych warstwach geologicznych na obszarze składowiska odpadów Nam Son przy wykorzystaniu metod hydro-geofizycznych. W badaniach budowy geologicznej terenu wykorzystano metodę obrazowania elektrooporowego (Electrical Resistivity Tomography – ERT), metodę potencjałów własnych (Self-Potential – SP) oraz badania elektromagnetyczne bardzo niskich częstotliwości (Very Low Frequency – VLF). Wytypowano trzy profile (o całkowitej długości 900 m) do dwuwymiarowego obrazowanie ERT oraz siatki gęstości do badania elektromagnetycznego VLF oraz 180 rozproszonych punktów do badań metodą potencjałów własnych na badanym terenie. Próbki wód powierzchniowych i gruntowych do analizy chemicznej pobrano z 10 lokalizacji na terenie składowiska. Interpretacja danych geofizycznych wykazała istnienie strefy charakteryzującej się niskimi oporami (<15 Ω), w pełni nasyconej odpadami ciekłymi wypłukiwanymi z otwartego składowiska. Stwierdzono wysoki poziom korelacji pomiędzy rezultatami badań geofizycznych a wynikami analiz chemicznych.

3

Near-surface study of a hot spring site in Fiji

Lal A., Deo R. N., Kumar A.

Acta Geophysica

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2018

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Vol. 66, no. 4

659--672

EN

A geophysical investigation of a hot spring system located in Rabulu, Fiji, was carried out from October 2014 to March 2015. The investigation covered a survey area of 6075 m2. Self-potential (SP), ground temperature and soil carbon dioxide (CO2) concentrations were measured and investigated for their distribution characteristics and inter-linkages. Results indicated obvious anomalous zone at the hot spring discharge site. The SP profile analysis highlighted thermal water upwelling zones and elevation-driven subsurface groundwater pathways. Measurement of subsurface temperatures up to 1 m depths revealed increasing temperatures, indicating potentially high thermal gradients in the area. Surface soil CO2 distributions also agreed with SP and ground temperature results. The overall result of the study demonstrated that synchronised measurements of SP, ground temperature and soil CO2 can be instrumental in identifying anomalous zones near the hot spring sites. Other parameters such as spring water temperature, discharge rate and energy flux estimates from the spring were calculated and analysed. The high-dense multi-parameter data coverage allowed interpretation of geothermal features at a scale never conducted in Fiji before. The near-surface investigations reported in this study corroborate previously suggested steady geothermal activity in the region, deserving further detailed investigation.