2D/3D inversion of geomagnetic data for characterization of the Tulu Moye geothermal reservoir, central main Ethiopian rift, Ethiopia

Owing to its location in the active parts of the East African Rift System, the Ethiopian Rift System defined by weakening lithosphere, active volcanism, and advanced levels of rifting exhibits geothermal manifestations. As a consequence, the Ethiopian Rift System is one of the promising areas for geothermal resource development and as such roughly 120 locations inside the ERS had their own heating and circulation systems. Seven of these areas have been identified as most promising. One of these geothermal areas is the Tulu Moye geothermal prospect (the subject of this study), found at the eastern margin of the Central Main Ethiopian Rift. Ground-based high density (92000 points) total intensity magnetic data were acquired and analyzed to determine the presence of hydrothermal alteration caused by thermal activity as well as map the extent and geometry of the geothermal reservoir. To minimize the remnant magnetic field effect, the magnetic field was Reduced-to-Equator (RTE) and the results were utilized to produce 2D/3D inversion sections. A number of 2D magnetic anomaly models produced from the RTE anomaly that show a wide range of anomaly values (−424 to 590.2 nT) are used to characterize the geothermal prospect. Further, 3D models were generated to examine the extent and geometry of the reservoir. The highest positive magnetic anomaly (related to strong rock demagnetization in the RTE but depicted in reverse) is focused in the central sector of Tulu Moye inferred caldera. Within the central sector, the northern portion of Tulu Moye with an approximate area of 100 km² is presumed to be the location of the main geothermal reservoir. More specifically, an area west of Salen mount extending from Teru Moye to Giano following the Wonji Fault Belt, and an area east of Salen which extends from Gnaro to Belale are suggested to be appropriate locations for exploratory geothermal boreholes.