Velocity and Strain in the Afar Rift from Sentinel-1 InSAR

The Afar Rift represents the transition between continental rifting in the Main Ethiopian Rift (MER) and sea-floor spreading in the Red Sea Rift (RSR). How magmatic spreading segments in Afar accommodate this transition on broad spatial and temporal scales remains unclear. We develop a time series of Sentinel-1 interferometric synthetic aperture radar (InSAR) observations of ground deformation covering the whole Afar Rift from 2014-2019 to study the distribution of strain across all magmatic segments in Afar. In particular, we focus on the persistent post-rifting relaxation signal at the Dabbahu-Manda-Hararo (DMH) segment, following from the 2005 rifting episode. We measure an uplift rate over the last 4.5 years at the segment centre of 30 +/- 5 mm/yr, and rift-perpendicular extension rates of 25 +/- 5 mm/yr. These rates show the post-rift uplift and extension have slowed from < 80 mm/yr and < 110 mm/yr respectively, measured between 2005-10 (Pagli et al., 2014). We investigate different mechanisms for this continued deformation, including a lower-crustal viscous response and ongoing magma movement. We discuss the implications of strain focussed rifting in Afar and the behaviour of spreading centres in general.