Use of Electrical Resistivity Tomography in investigating the internal structure of a landslide and its groundwater characterization (Nanka Landslide, Anambra State, Nigeria)

Abstract

ABSTRACT Over two decades, this landslide in Nanka Community, Anambra State, Nigeria, in the eastern phase of Awka-Orlu upland, has been active and persistent, defying many control measures that have been put in place and causing the loss of property, lives, and assets to increase. As a result, this research work involves the study of geo-engineering and geophysical measurements of the slide site to delineate the aerial scale and direction of movement of the landslide zone, determine the lithological portion, estimate the thickness of the sliding sheet, and delineate the water-saturated areas. The data was collected using ABEM Terrameter SAS 4000 and ABEM LUND ES464 electrode selector system and processed using RES2DINV software for a 2D subsurface image. During data acquisition, a Wenner array was set-up as this array is capable of imaging deeper profile data, and apparent resistivity is easily calculated in the field. The results of the models indicate that the study area was mainly clayey and sandstone formation with mostly low resistivity values correspond to the shale layers and groundwater zones. However, gravel deposit was also present in some areas, as indicated by both the imaging and geological measurements.