n Journal of Emerging Trends in Engineering and Applied Sciences - Effect of current variation on geoelectric sounding data quality and parameters in the Basement Complex terrain

Volume 5, Issue 3
  • ISSN : 2141-7016
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This study is aimed at evaluating effects of current variation on field data quality and reliability of derived geoelectric parameters within the Basement Complex rocks using the campus of Federal University of Technology, Akure as case study. The campus is underlain by quartzite, charnockite, migmatite-gneiss and granite-gneiss. Currents in the orders of 1, 2, 5, 10, 20, 50 and 100mA were injected. Acquisition and interpretation constraints (SD%) and RMS error respectively indicate that low currents of 1 - 5mA may provide good dataset within migmatite-gneiss, but low quality dataset within the other units. High standard deviation (s) of 4.37 and 7.061 obtained from quartzite and charnockite respectively explain low reliability of depth estimates within them at low currents while 0.6557 and 1.204 describe higher accuracy of depth estimates in granite gneiss and migmatite gneiss respectively. Low currents may enable fair environmental study assessment within charnockite (0.28≤S≤0.62; s = 0.1147) that exhibits heterogeneity at 1.06≤λ≤1.34 (s = 0.1212), migmatite-gneiss (0.026≤S≤0.029; s = 0.00098) that exhibits heterogeneity at 1.5≤λ≤2.24 (s = 0.3026) and granite-gneiss (0.023≤S≤0.026; s = 0.00168) that exhibits fair homogeneity (1.02≤λ≤1.14; s = 0.0.05273) while higher current (above 50mA) may be required to make reliable assessment in quartzite (0.04≤S≤ 0.14; s = 0.0441) that exhibits some heterogeneity (1.02≤λ≤1.11; s = 0.0.0315). Thus, low current injection in remote areas of similar lithologic setting where equipment charging is unachievable will still present credible results. However, acquisition of satisfactory dataset and derivation of accurate geoelectric parameters resulting in good verdict can be best served when geoelectric soundings are undertaken at 50mA and above.

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