ASTER-RADARSAT-DTED DATA INTEGRATION FOR 3D ILLUSTRATION OF THE AFAR DEPRESSION, ETHIOPIA

As one of the most impressive geological features on the planet, the Afar Depression in NE Africa provides a natural laboratory for studying the processes of sea-floor spreading and is the only place (together with Iceland) where the transition from rifting to true sea-floor spreading can be studied on land. Remote sensing (including optical and radar data) and topographic data integration is the process whereby different spatial data sets over the same region are combined and displayed in a single image. This integration involves optical and radar data fusion and draping the fused images onto a digital elevation model. We present results from the integration of the Advanced Spaceborne Thermal Emission Radiometer (ASTER), Standard Beam RADARSAT, and Digital Terrain Elevation Data (DTED) for aiding in mapping morphologically-defined structures in the Afar rift-rift-rift triple junction which is represented by the Red Sea, Gulf of Aden and the Ethiopian Main Rift. ASTER-RADARSAT data fusion is carried out using the Red-Green-Blue (RGB)-Intensity-Hue-Saturation (IHS)-RGB transformation and Color Normalization Transformation (CNT) techniques. The advantage of ASTER-RADARSAT data fusion is that the process allows displaying multi-spectral optical remote sensing data, which measure surface composition, with radar data which emphasize surface roughness and morphology. ASTER-RADARSAT fused images are draped over DTEDs to create a realistic three-dimensional perspective of the Afar triple junction and to examine the three-dimensional orientation of the morphologically-defined structures and their spatial relationship with lithological units. This process has significantly improved the display of the poor spatial resolution (1 km) DTED data since radar images are powerful in emphasizing morphology through radar shadow/illumination phenomenon. ASTER-RADARSAT-DTED data integration allowed us to estimate the slopes of fault scarps and locating marker horizons. In addition, the integration has allowed us to better visualize and interpret the extensional imbrication fans created by gravitation pull into the basins. This process will be of greater use to structural studies in extensional tectonic regimes when higher spatial resolution DEMs, such as those extracted from SRTM data, are made available.