SUBSURFACE STRUCTURAL CHARACTERIZATION, USING 2D ELECTRICAL RESISTIVITY TOMOGRAPHY AT NATIONAL ANIMAL PRODUCTION RESEARCH INSTITUTE (NAPRI), ZARIA, NIGERIA.

Abstract
The method adopted for this research work was the 2D Electrical Resistivity Tomography (ERT), using the ABEM LUND Imaging System. A Wenner configuration was carried out to map the electrical properties as an aid to characterizing the subsurface conditions. Eight profiles were occupied in the study area. For each profile, the layout geometry for the electrical imaging was such that two reels of cables were laid collinearly with 5m intervals between the takeout electrodes. Each reel had 20 takeout electrodes. However, the two innermost electrodes of the two reels of cables were connected together thus yielding effectively 41 electrodes and a spread length of 200m. The data obtained using ABEM Terrameter SAS4000 with electrode selector were processed using RES2DINV software. From the interpretation of the electrical images obtained in the study area, the depth to the fresh basement is generally well beyond 29.3m. The study reveals the presence of two distinct layers; the topsoil and the weathered basement with resistivity ranges of 20-400m and 30-470m respectively. These two layers constitute the overburden with a minimum thickness of 29.3m as revealed by the pseudosections. This is the maximum depth of probing achieved in the present study. The topsoil, composed of laterite and brownish sandy clay, has a thickness of about 5.0m to 7.0m. The weathered basement underlies the topsoil with a thickness of about 22.3m to 24.3m and this is the good aquifer in the study area. This layer has a relatively low resistivity due to the presence of water. The layer is highly weathered and the degree of weathering increases towards the fresh basement. This increased thickness of bedrock weathering is a proof of the capability of this layer to provide a good water reservoir with a high probability of the presence of fractures in the weathered basement. The maximum depth of probing achieved in the present study is 29.3m; this is less than the depth to the fresh basement. Hence, there is no information about the fresh basement.
Description
A THESIS SUBMITTED TO THE POSTGRADUATE SCHOOL, AHMADU BELLO UNIVERSITY, ZARIA IN PARTIAL FULFILLMENT FOR THE AWARD OF THE DEGREE OF MASTERS OF SCIENCE IN APPLIED GEOPHYSICS. DEPARTMENT OF PHYSICS FACULTY OF SCIENCE AHMADU BELLO UNIVERSITY, ZARIA
Keywords
SUBSURFACE, STRUCTURAL, CHARACTERIZATION,, USING, 2D ELECTRICAL, RESISTIVITY, TOMOGRAPHY, NATIONAL, ANIMAL, PRODUCTION, RESEARCH, INSTITUTE, NAPRI, ZARIA,, NIGERIA.
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