| dc.description.abstract | The D. C. electrical resistivity study of Suswa-Olkaria
region was carried out from July 1987 to November, 1988.
The main objective was to evaluate the sub-surface
geoelectric structure with a view to determining layers
that might be associated with geothermal fluid
migrations. The study also aimed at delineating the
southern extent of the Olkaria geothermal field and of
the structural discontinuities. The study was carried
out using the Symmetrical Schlumberger array with a
maximumcurrent electrode spacing of 8000m.
The resistivity data analysis was carried out by curve
matching and fitting, and 1-D iterative computer
modelling. Geoelectrical structural models on line
profiles have identified horst-graben structures bound by
normal to oblique N-S and oblique arcuate E-W trending
discontinuities. Some of these discontinuities coincide
with fault zones which are permeable zones of complex
fluid migration. Geophysical and Geological data
synthesi~ has identified four geoelectrical units with
considerable variation in thickness. These are the
overburden, a resistive cap rock, a conductive unit (3-15
Om) and an electrical basement (50-2000m) . The
resistivity of the conductive unit in the southern part
of Olkaria is similar to that of Olkaria West. The
conductive unit correlates with tertiary pyroclastics
rintercalated
with tuffs rhyolite and trachytes while the
electrical "basement" correlates with Miocene Volcanics.
From this study, it is noted that the graben structures
with a sub-surface conductive unit which is covered with
a resistive "cap" rock offer good prospects for further
geothermal exploration. The conductive unit has been
attributed to a permeable layer that is part of a
convective hydrothermal cell. The conductive unit
continues southwards through the present area of study. | en |
