Surface displacements in the September 2005 Afar rifting event from satellite image matching: Asymmetric uplift and faulting

Abstract

Combining sub‐pixel analysis of SPOT4 images with InSAR measurements, we generate 3D surface displacements for the September 2005 rifting event on the Dabbahu Segment in the Afar valley. The axis of rifting in the event is shifted to the east of the geomorphic rift. The horizontal displacements reveal 6 m of extension, and vertical displacements show asymmetric uplift of the flanks of the dike. Simple forward modelling indicates this asymmetry is due to the dike dipping 80° to the west towards the geomorphic rift. The boundary between eastward and westward displacements aligns with the transition between uplift and subsidence on the east in the north part of the segment, but on the west in the south. Normal faulting is not required on both sides of the instantaneous rift. East‐dipping normal faulting on the west side of the instantaneous rift aligns with a west‐dipping normal fault in the topography.

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