Applications of Integrated Geophysical Techniques to Map Subsurface Structures, Contributing to Ground Water Flow in the Ziway – Langano Corridor, Central Main Ethiopian Rift
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Date
2017-06
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Addis Ababa Universty
Abstract
The aim of this MSc thesis is to evaluate subsurface structural influences on groundwater flow in the
Ziway - Langano Corridor area located in the central main Ethiopian rift using integrated
geophysical methods which include gravity and magnetic method. The study is deemed to be an
essential resource in evaluating the subsurface geologic structures. The surface geology of the study
area ranges in composition from volcanic rocks of rhyolite, pyroclastic, obsidian, and ignimbrite
rocks, to sedimentary rocks of lacustrine sediment and alluvial deposits. It is determined that the
tectonic setting and rock types of an area are important in establishing the distribution of the
groundwater flow.
Existence of subsurface structures which include faults, fractures, and veins have been investigated
in the Ziway – Langano Corridor using horizontal gradient gravity map and tilt derivative magnetic
map compiled for the study area. These geophysical investigation results have identified subsurface
geologic structures which are responsible for the flow of groundwater from Lake Ziway towards
Lake Langano.
In addition to this, field observations made during the magnetic survey have confirmed the flow of
ground water from Lake Ziway towards Lake langano. This conclusion is also confirmed by the
existence of hot springs at the northern shore of Lake Langano which is missing at the southern
shore of Lake Ziway.
This work has shown that there are no east west structures that favor the flow of groundwater.
Hence, the direction of groundwater flow in the study area takes place from Lake Ziway towards
Lake Langano being controlled by the N-S and NE-SW oriented faults and fractures mapped in the
Ziway – Langano corridor.
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Keywords
Ziway – Langano Corridor