Browsing by Author "Woyema Duresa"

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    Applications of Gravity and Magnetic Methods to Map Subsurface Structures, Contributing to Ground Water Flow in The Bulbula-Arsinegele Rift Corridor, Central Main Ethiopian Rift.
    (2018-06-01) Woyema Duresa; Alemu Abera (PhD)
    Analysis of newly acquired magnetic and existing gravity data constrained by the existing geologic information is made in order to delineate and map the subsurface geologic structures contributing to groundwater flow within the Bulbula-Arsi Negele rift corridor. Data enhancement (filtering) techniques have been applied both to the observed gravity and magnetic data in order to highlight the anomaly components resulting from deeper and shallower sources. The compiled residual anomaly map and its derivatives (regional, residual maps) reveal that relatively positive values which coincide with the locations of the Aluto volcanic center, Munesa ridge and high density basalt, rhyolite intrusion and extrusion of the Shala caldera. Correspondingly, the compiled magnetic anomaly maps including its derivatives (regional and residual maps) revealed that the volcanic centers residing the Aluto and Shala volcanic center and the Munesa basalt, rhyolite intrusion and extrusion are associated with relatively high magnetic anomalies. Relatively low magnetic anomalies are associated with the sediment dominated around the shore of Lake Langano, Lake Abijata, Lake Shala and the surrounding of Bulbula and O’itu towns. The horizontal gradient gravity map and tilt derivative magnetic map compiled for the study area have determined the existence of NE-SW and N-S lineated subsurface geologic structures (faults and fractures) that favor the flow of groundwater from Lake Langano towards Lake Abijita and Lake Shala. This M.Sc. thesis research has shown that there are no east west lineated structures that favor the flow of groundwater from Lake Langano towards Munesa ridge. Hence, the direction of groundwater flow in the study area takes place from Lake Langano towards Lake Abijita and Lake Shala being controlled by the N-S and NE-SW oriented faults and fractures mapped in the study area.