Teshome, Daniel Mamo (2014) Integrated Gophysical Investigation for Chew Bahir Lake Bed Characterization, Southern Ethiopia. Masters thesis, Addis Ababa University.
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PDF (Integrated Gophysical Investigation for Chew Bahir Lake Bed Characterization, Southern Ethiopia)
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Abstract
This thesis encompasses ground geophysical investigations and examination of previously collected geophysical data at the Chew Bahir, Chelbi Southern Ethiopia. The objectives of the survey was to characterize the Lake bed and proposed core drill sites and check their suitability for obtaining continuous core samples for paleohistory and paleoenvironmental studies. The earlier collected geophysical data include patented seismic data collected by Tullow Oil Plc. The firsthand field data contain electrical resistivity tomography (ERT) and vertical electrical soundings (VES) data over three locations i.e. at the planned core drill site, at an alternative drill site, and at a location adjacent to the valley sides across one of the major alluvial fans. Upon analysis, data from the regional seismic show a dipping bedrock surface away from the valley sides towards the basin center with the suggestion of greater than 5km of unconsolidated sediment at the basin center. The electrical imaging field data map the subsurface to an estimated 70 m below the Lake bed. The results revealed very low apparent resistivity within the basin‟s Lake bed sediments (characteristically less than 1 Ωm), with significantly higher apparent resistivity through the alluvial fan at the valley side (often greater than 500 Ωm). Inside the very low resistivity area, contrary to the expected horizontally stratified subsurface, small lateral resistivity inhomogeneities were exhibited that are possibly associated with lithological changes and changes in desiccation history. The geophysical signature associated with the alluvial fans was clearly distinguished at the valley side, but no signal of similar features was found over the two suggested drill sites. Based on the geophysical survey to date, a location of UTM 261829N and 521120E is recommended for drilling in a sequence of somewhat uniform Lake deposits.
| Item Type: | Thesis (Masters) |
|---|---|
| Uncontrolled Keywords: | Electrical Resistivity Tomography, Vertical Electrical Sounding, Seismic Refraction, Inverse Model Sections, Chew Bahir |
| Subjects: | Q Science > Q Science (General) Q Science > QE Geology |
| Divisions: | Africana |
| Depositing User: | Selom Ghislain |
| Date Deposited: | 25 Sep 2018 09:59 |
| Last Modified: | 25 Sep 2018 09:59 |
| URI: | http://thesisbank.jhia.ac.ke/id/eprint/5703 |
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