Mapping lateral extent of Suevites at Northern Part of Lake Bosumtwi using resistivity and seismic refraction methods
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Date
May , 2016
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Abstract
Electrical resistivity imaging and seismic refraction method have been used to
map the lateral extent of suevites in northern lake of Bosumtwi. Seven electrical
resistivity tomography and two seismic refraction pro les were surveyed. The
lengths of the pro les varied between 160 and 600 m. The multi electrode system was combined with roll along techniques for resistivity data collection using
gradient array. Roll along was also executed for the seismic refraction survey
where two geophones were overlapped to extend the survey length. The data was
acquired in 2D where 4 m as electrodes separation was also equal to geophones
spacing, while shooting interval was 8 m. Depth of investigation for resistivity and
seismic refraction surveys are 25 m and 26 m respectively. Data was processed
with Res2dinv and Re
exW for the resistivity and seismic refraction respectively.
Electrical resistivity and seismic refraction tomography identi ed fractured zones
as well as suevite deposits which were observed within 12 m depth. Resistivity
of northern Bosumtwi suevites varies between 1.56 and 25
m, and the P wave
velocity ranges from 3000 to 3900 m/s. The results also showed that the subsurface is made up of either two or three layers: unconsolidated top soil and moist
clay, soil with moisture content or clayey soil and fractured claystone. The seismic refraction tomography and the electrical resistivity tomography agree well in
revealing subsurface geological units based on their velocity and resistivity values
Description
A thesis submitted to the Department of Physics, Kwame Nkrumah University of Science and Technology in partial fulfillment of the requirements for the degree of Master of Philosophy (Geophysics),