Ground Magnetic Attributes For Subsurface Structural Analysis of Foundation Beds in a Sedimentary Terrain in Southwestern Nigeria: OSUSTECH Permanent Site as a case study

Abstract

The structural failure such as subsidence, collapse and cracking of the walls of buildings in Nigeria has posed a threat or a significant potential hazard to the community in the affected areas. These hazards include gross loss of valuable lives and properties that always accompany such structural failure. Therefore there is need for subsurface structural analysis. The Stop-And-Go method was used for the acquisition of the data. This method is good for subsurface investigation at depths below 30 metres (100 feet). Data for this study were taken at a 10 metres station spacing which is about half that of the expected depth of target. The method requires the technique of measuring total field components at discrete points along the traverses distributed regularly throughout the survey area of interest. The raw data were processed to remove diurnal variations from the total field data measured from the base station. Interpretation of the ground magnetic data revealed that the study area comprises zones underlain with thin to thick overburden. In all the profiles, the regions A and B are associated with the high magnetic values except in the profile 4 in which only region E is associated with high magnetic values. Thus, the region E in the profile 4; the regions A and B in the profiles 1, 2, 3 and 5 are competent zones for the sitting of structures. It can be deduced that the regions of high magnetic susceptibility and high resistivity are competent zones for construction of high rise buildings and other engineering structures. While the regions of low magnetic susceptibility and low resistivity could pose problem of subsidence of the buildings around the region.