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Paper Number: 196
Groundwater
exploration using electromagnetic frequency domain and electroseismic
sounding methods in Kalahari sands and Karoo Sequence in Zimbabwe.
Zulu, J.M.
Josrum Enterprises 129 A Fort Street, Albion Flats, 2nd
Floor, Office Suite 5 Room 3, Bulawayo, Zimbabwe. Email Address:
zulujosephm@yahoo.com.
______________________________________________________________
Abstract
Exploration for groundwater resources for community water supply was
carried out in the Kalahari sands underlain by sandstone, mudstone and
basalt of the Karoo Succession. Occurrence of groundwater in the
geological formations is controlled by primary porosity of the sands as
well as fracturing and weathering of the basalt. The geological
formations form important aquifers exploited for water supply by means
of drilled boreholes. A complementary use of geophysical methods in
conjunction with geology, approach was used in site investigations.
Electroseismic survey method was used to complement the electromagnetic
frequency domain method. Electromagnetic profiles were carried out on
the target areas. Anomalies identified were further investigated using
electroseismic sounding and the results were used to identify potential
sites for drilling boreholes. The results of the sounding were presented
in the form of a sounding curve. The sounding curves were interpreted
using forward modelling assuming that waves generated during the survey
had typical seismic velocity values when passing through geological
formations in the areas under investigation leading to a hydrogeological
model for the area. A geological model for an area under investigation
was determined from literature and field observations. A comparison of
driller’s logs for areas where boreholes were drilled, with models
generated from geophysical survey results from groundwater exploration
was also done.
Key words: electroseismic sounding, electromagnetic
profiling, forward modelling, seismic velocity, geological model,
hydrogeological model.
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