Evolution of the Afar Depression from orbital optical and radar images, Ethiopia

A combination of far-field stress due to slab-pull of the Arabian plate along the Zagros Orogenic Front and upwelling of the Afar mantle plume led to the formation of the Afar Dome and reciprocating tectonic and volcanic activity. When the Afar Dome was sufficiently stretched it collapsed to form the Afar Depression and main structural trends defined by the Main Ethiopian, Red Sea and the Gulf of Aden rifts. Subsequently, an anti-clockwise rotation and northward translation of the Danakil Block, clock-wise rotation of the Ali-Sabieh and the East-Central Block resulted in the development of the Red Sea, the Gulf of Aden and the Main Ethiopian Rift segments within the Afar Depression. The interactions of the Red Sea, the Main Ethiopian Rift and Gulf of Aden trends in the southern Afar defined: (1) A rift-rift-rift triple junction of the kinematically coupled Main Ethiopian Rift and the Red Sea rift, and the Gulf of Aden; and (2) An overlap zone (East-Central Block) bounded by the SE-propagating Manda Hararo-Gobaad and the NE-propagating Asal-Manda Inakir principal rifts. Interpretation of RADARSAT images indicate an early simultaneous displacement of the Arabian and Somalian plates from the Nubia Plate along the Main Ethiopian Rift and the Red Sea coupled structures. The overall Red Sea and Gulf of Aden rift propagation and local rift jumps within the southern Afar Depression suggest that further propagation along the same trend is likely to be stalled. The geometry of the overlap zone favors the localization of rift extension within the East-Central Block (overlap zone). Ultimately the plate boundary separating the Arabian plate from the Nubian-Somalian Plate will develop inside the overlap zone connecting the Red Sea and Gulf of Aden trends along the tectonically active path of the Dobi, Dobi-Hanle, Der Ela-Gaggade and Asal grabens. The Dobi Graben is characterized by NW-trending high-angle normal faults, sinistral strike-slip faults and NE- and NW-dipping, layer-parallel, down-dip gravitational slip planes. The layer parallel displacement resulted in the formation of stacks of anti-clockwise rotated graben-bounded extensional imbrication fans.