SUBSURFACE STRUCTURAL CHARACTERIZATION, USING 2D ELECTRICAL RESISTIVITY TOMOGRAPHY AT NATIONAL ANIMAL PRODUCTION RESEARCH INSTITUTE (NAPRI), ZARIA, NIGERIA.
SUBSURFACE STRUCTURAL CHARACTERIZATION, USING 2D ELECTRICAL RESISTIVITY TOMOGRAPHY AT NATIONAL ANIMAL PRODUCTION RESEARCH INSTITUTE (NAPRI), ZARIA, NIGERIA.
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Date
2012-10
Authors
JOHN, ADAMU,
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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 20-400m and 30-470m 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.