Getaneh, Assefa (2007) Characterization of Major Subsurface Structures in Ada'a Plain Using Intergated Geophysical Survey. Masters thesis, Addis Ababa University.
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PDF (Characterization of Major Subsurface Structures in Ada'a Plain Using Intergated Geophysical Survey)
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Abstract
This manuscript presents the results of geophysical data analysis from Ada'a plane with a primary objective of characterizing major subsurface structures and their connection to the subsurface hydraulic system. Towards this end, verifying a barrier, inferred through preliminary interpretations and conceptualizations of the ground water system in the plane by Water Works Design and Supervision Enterprise (WWDSE), was the primary task of this work. Ada'a ground water is located in the southern Awash Basin, Oromiya Regional State, between geographical coordinates of 38050'E - 39015'E and 8030'N - 8045'N. The geophysical data set employed in this project includes: the potential field methods namely Gravity and Magnetics and are used to investigate major subsurface structures. The other method found adequate for this study is the electrical resistivity method as it is used to evaluate ground water potentials. Regional and residual Bougeur anomaly contour maps revealed large scale regional subsurface structures that align along the rift and small scale, local subsurface structures showing different orientation. The residual feature with a discordant structural alignment shows spatial correlation with the expected subsurface barrier. The total field magnetic contour map also confirms this indication and gave further evidence for the existence of such anomalous feature in the area of interest. A depth-slice stack map of apparent resistivity of fifty VES data also manifested a subsurface feature that coincide to the anomaly revealed by the residual gravity map. Deep, low apparent resistivity responses, which can safely be interpreted as water saturated, aquifer zones, are separated by a high resistivity, elongated feature. This feature could represent an impermeable dry rock units related to domes and cones of intermediate magma that can possibly impede the ground water movement. Inversion of 2D electrical resistivity imaging data gave a clear subsurface picture and depicted the geo-electric substratum, which is a resistive dry bottom, to rise above the expected water table at the speculated region. Though it falls short to cover the lateral extension of the inferred barrier, it presented strong evidence that supports findings from the other methods. A 1D apparent resistivity pseudosection along VESs 54,55,56,58 and 59 reflect the geologic reality as they traverse across a high resistive formation where the barrier is expected lying and complement the results of the 2D analysis.
| Item Type: | Thesis (Masters) |
|---|---|
| Subjects: | Q Science > Q Science (General) Q Science > QC Physics Q Science > QE Geology T Technology > T Technology (General) |
| Divisions: | Africana |
| Depositing User: | Selom Ghislain |
| Date Deposited: | 06 Sep 2018 14:45 |
| Last Modified: | 06 Sep 2018 14:45 |
| URI: | http://thesisbank.jhia.ac.ke/id/eprint/4939 |
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