Geophysical Investigation of Fracture Distribution in the premises of Nigerian Stored Products Research Institute (NSPRI), Ilorin

Abstract

This work aimed at studying the geological fracture system in the study area. It gives an insight into the proper infrastructural planning such as the location of high-rise buildings, septic tank locations, groundwater exploration, etc. Aeromagnetic and Very Low Frequency (VLF) techniques were employed to investigate fractures within the Nigeria Stored Product Research Institute (NSPRI) premises in Ilorin. A reconnaissance magnetic anomaly map encompassing longitude 4°33'10" - 4°33'30" and latitude 8°27'10" - 8°27'40" was generated from aeromagnetic secondary data collected by the Nigerian Geological Survey Agency (NGSA) via aero-surveys over the Nigeria surface area. Conversion to data format and data processing were accomplished utilizing Oasis Montaj 6.4.2 9(HJ) software. Analysis revealed a series of minor fracture signatures and lineament trends with two major northeast-trending fractures, 401 m and 560 m long, in the premises of NSPRI. For confirmation three VLF profiles were run across the major strike of the detected major fractures. The real component signal of the first profile ranges from (-56 to 66 %), second (-18 to 18 %), and third (-12 to 20 %) while the imaginary component signal of the first profile ranges from (-16 to 20 %), second (-27 to 4 %) and the third (-13 to 21 %). Interpretations, using karous-Hjelt filtering software, show real and imaginary crossovers which is a signature of fractures on these three profiles. This confirmed the two prominent fractures earlier detected. In conclusion, the area shows that there are minor fractures in the NW - SE and SW - NE directions and two major fractures are in the direction of NW - SE direction and VLF-EM survey confirms the presence of the two major fractures detected in the area.