Application of Gravity and Magnetic Methods to Characterize Subsurface Structures Contributing to Ground Water Flow in the Meki-Bulbula Rift Corridor, Cmer
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Date
2018-05-05
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Addis Ababa University
Abstract
The objective of this MSc thesis is to characterize subsurface structural influences on groundwater flow in the Meki-Bulbula rift Corridor located in the central main Ethiopian rift using integrated geophysical methods namely, gravity and magnetic methods.
The surface geology of the study area ranges in composition from volcanic rocks of rhyolite, pyroclastic, obsidian, and ignimbrite rocks, to 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 and orientation of subsurface linear structures, which may include faults, fractures, and veins have been investigated in the Meki-Bulbula rift 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 Meki to Bulbula. The depth, distribution and location of the subsurface geologic structures have been shown by Euler deconvolution gravity and magnetic maps.
Additionally, 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 Meki – Bulbula corridor.
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Application of Gravity, Magnetic Methods, Characterize Subsurface, Structures Contributing, Meki-Bulbula Rift Corridor, Cmer