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2 Acta Geophysica

2 2023

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Ionospheric perturbations: a case study of 2007 five major earthquakes using DEMETER data

Thomas Jewel Emem, Ekanem Aniekan Martin, George Nyakno Jimmy, Akpan Anthony Effiong

Acta Geophysica

2023

Vol. 71, no. 4

1607--1618

Using the Plasma analyzer (IAP) and Langmuir Probe (ISL) experiments of the Detection of Electromagnetic Emissions Transmitted from Earthquake Regions (DEMETER) lithospheric–atmospheric–ionospheric coupling has been observed before, during and after five major earthquakes with magnitudes greater than 6.5. The aim of this study is to use ionospheric parameters to identify the ionospheric perturbations associated with the five earthquake regions screened. All the three investigated ionospheric parameters of electron density, electron temperature and total ion density recorded perturbations within the investigative period. A total of 36 anomalies were obtained with 18 each for nighttime and daytime readings. The observed anomalies being screened for false alarm using the geomagnetic indices of Kernnifzer digit (kp) and disturbance storm time (Dst.) revealed 27.8% as geomagnetically induced perturbations. Thus, 72.2% of the studied anomalies transpired in quiet geomagnetic conditions, which is linked to seismic events.

Contribution of electrical prospecting and spatiotemporal variations to groundwater potential in coastal hydro-sand beds: a case study of Akwa Ibom State, Southern Nigeria

George Nyakno Jimmy, Agbasi Okechukwu Ebuka, Umoh James Anthony, Ekanem Aniekan Martin, Ejepu Jude Steven, Thomas Jewel Emem, Udoinyang Ifiok Efiong

Acta Geophysica

2023

Vol. 71, no. 5

2339--2357

The current study used vertical electrical sounding (VES), borehole (BH) data, Remote Sensing (RS), and Geographic Information System (GIS) techniques to identify groundwater potential zones in the coastal area of Akwa Ibom state, Nigeria, for the first time. This research aimed at producing groundwater potential zone map that can divide the study region into separate zones based on their groundwater potential ranking. The deployed method integrated VES procedure utilizing the Schlumberger electrode configuration some core samples for estimation of porosity, Satellite Shuttle Radar Topography Mission (SRTM), Digital Elevation Model (DEM), which served as input data for RS and GIS. Thematic maps of lineament density, lithology, land use and land cover, drainage density, and slope were created as GIS layers in a geo-database. Weightages were assigned based on a pair-wise assessment of the components that appear to be essential in retaining, storing, and transporting groundwater. The Analytical Hierarchy Process (AHP) was used in a GIS setting to merge five thematic maps of elements controlling groundwater occurrence and movement using weighted overlay. Results show that aquifers with high thickness and depths are clustering around VES 9, VES 14, and VES 15 that have the highest aquifer thickness in the range of 219–262 m and the highest aquifer depth in the range of 222.09–264.74 m. The highest aquifer resistivity in this area ranges from 2963 to 3683 Ωm. The hydraulic conductivity of the area is highest around the south-eastern part of the study area, with maximum value of 3.43 m/day. The transmissivity increases in the northern part of the study area, while the eastern parts showed the lowest values. The highest aquifer resistivity in this area ranged from 2963 to 3683 Ωm. Inference from analysis indicated that the most important element was soil type (43%), followed by lineament density (33%) and slope (13%). Land use/land cover was discovered as a marginal contributor to groundwater in the research region, accounting for about 4% of the total contributors. The study CR determined to be 0.043884, is much lower than the 0.10 consistency threshold and hence the justification of the results. The result of the overlay of the geophysical survey on the groundwater potential zones obtained from the RS, GIS, and VES techniques done in the first time in the study area has shown seamlessly that the study area has high groundwater prospectivity for subsistent and commercial extractions.