2D/3D Analysis of Magnetotelluric Data in the Central Main Ethiopian Rift (CMER): Implications for Geothermal Resources
| dc.contributor.advisor | Shimeles Fisseha | |
| dc.contributor.advisor | Bekele Abebe | |
| dc.contributor.author | Aklilu Abossie | |
| dc.date.accessioned | 2025-08-27T08:14:01Z | |
| dc.date.available | 2025-08-27T08:14:01Z | |
| dc.date.issued | 2024-01 | |
| dc.description.abstract | The Main Ethiopian Rift (MER) is a seismically and volcanically active portion of the East Africa Rift System (EARS). In the Central Main Ethiopian Rift (CMER), there are several active volcanoes and calderas that are known to be constantly changing, with periods of rising and sinking. Geothermal resources are often associated with these active volcanoes. This dissertation deals with the analysis of the 2D/3D crustal geoelectric models obtained through 2D joint (TE - transverse electric and TM - transverse magnetic modes) inversion of magnetotelluric (MT) data across CMER and a 3D inversion model from one of the hydrothermal occurrences in the CMER, Ashute geothermal field, which is found close to the western escarpment. This is aimed at investigating heat sources, heat flow paths, and geothermal resources to delineate and characterize the geothermal structures and comprehend the tectono-magmatic setting of the crust beneath the study area. Furthermore, the static shift correction data were used to obtain better and more accurate estimates of subsurface resistivities structure and thicknesses by using 1D joint inversion of TEM and MT data in the Ashute area. Based on the 3D inversion resistivity model, the subsurface beneath the Ashute geothermal site can be described by three main geoelectric layers. The top layer, which is relatively thin and highly resistant (> 100 Ωm) and extends down to 400 m depth, consists of unaltered volcanic rocks near the surface. Below this is a conductive layer (< 10 Ωm) with a maximum thickness of 1 Km, likely caused by the presence of clay layers (smectite, illite/chlorite zones) resulting from the alteration of volcanic rocks. In the third and deepest layer resistance of the subsurface gradually increases to an intermediate range (10–46 Ωm). This could be linked to the formation of high-temperature alteration minerals such as chlorite and epidote at depth, indicating the presence of a heat source. Similar to a typical geothermal system, the increase in electrical resistance below the conductive clay layer may suggest the existence of a geothermal reservoir Otherwise, no exceptional low resistivity (high conductivity) anomaly is detected at depth. The phase tensor analysis results across the CMER show a small beta value at low periods (nearly below 10 s), which indicates 1D or 2D structures, while at long periods (> 10 s), the data show 3D structures with a large value of |β| > 30. This asserts that the 2D inversion model can suitably describe the resistivity structures of the shallow crust. The dominant geo-electrical strike is estimated to be N150E using a Z-invariant and phase tensor azimuth. The results of 2D joint inversion of TE and TM modes seemingly identified partial melt within an upper crustal fracture zone (fault) with a resistivity of less than 5 Ωm at a depth of 12–22 km. This partial melt extends beneath the SDFZ with a width of approximately 10 kilometers horizontally. It could be related to the source of heat for the Ashute and Aluto geothermal fields. | |
| dc.identifier.uri | https://etd.aau.edu.et/handle/123456789/7146 | |
| dc.language.iso | en_US | |
| dc.publisher | Addis Ababa University | |
| dc.subject | Magnetotelluric | |
| dc.subject | TEM | |
| dc.subject | Dimensional Analysis | |
| dc.subject | Strike Analysis | |
| dc.subject | Joint Inversion | |
| dc.subject | Static Shift | |
| dc.subject | Geothermal Field | |
| dc.subject | Resistivity | |
| dc.subject | 2D Inversion | |
| dc.subject | 3D Inversion | |
| dc.subject | Ashute | |
| dc.subject | CMER | |
| dc.subject | Ethiopia | |
| dc.title | 2D/3D Analysis of Magnetotelluric Data in the Central Main Ethiopian Rift (CMER): Implications for Geothermal Resources | |
| dc.type | Thesis |