Understanding Regional Structural Framework of Borena and the Surrounding Regions in the Southern Main Ethiopia Rift (SMER), Ethiopia

Abstract

This study integrates remote sensing data via Digital Elevation Model (DEM) extracted from SRTM and satellite gravity data to detect surface and subsurface geologic structural features of Borena and the surrounding regions in the Southern Main Ethiopia Rift (SMER). Shading from different azimuth with 45-degree interval and tilt angle method were used to map lineaments and detect edges of anomalies from Digital elevation model and gravity data, respectively. The surface geology of the study area comprises alluvial and elluvial sediments deposited during of Holocene age, pre-rift and rift volcanics (basaltic rocks) and Precambrian banded gneiss. The Ririba rift and Mega rift systems make the main structural fabric of the area. About 793 lineaments from Digital elevation model data and, 441 from gravity data were outlined and their orientations were statistically analyzed using rose diagrams. These aretrending dominantly to NW–SE and N–S directions. Lineament depth map obtained from gravity data analysis suggests that the depth ranges from 300 m to more than 7 km below the ground with most of the lineaments are at shallow depth. The results obtained agrees with the main tectonic features found in the study area such as the N–S oriented Ririba rift and Chewbahir Rift and the NW–SE trending Mega fault zones.The integration of remote sensing data viz Digital elevation model and satellite gravity data has facilitated delineating structural features in studying the regional geological makeup of large area.