Abstract
Processes that facilitate the transition between continental rifting and
sea-floor spreading remain unclear. Variations in the spatial
distribution of extension through Afar and into the Red Sea are
indicative of temporal evolution of the rift. 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 extension across all magmatic
segments. By incorporating GNSS observations, we resolve 3D average
velocities in the vertical, rift-perpendicular, and rift-parallel
directions. Results show the spatial distribution of long-term plate
motions over the rift, as well as deformation at individual volcanic
centres, including Dallol, Nabro, and Erta ’Ale. We find that in
northern and central Afar, the majority of extension is accommodated
within +/- 15-30 km of magmatic spreading centres. In southern Afar,
near the Nubia-Arabia-Somalia triple-junction, extension is distributed
over 90-180 km, which may indicate an increase in rift focussing with
rift maturity. We also observe rapid surface uplift and
rift-perpendicular extension at the Dabbahu-Manda-Hararo segment with
velocities of 33 +/- 4 mm/yr and 37 +/- 4 mm/yr respectively. These are
higher than the background extension rate of 18-20 mm/yr, but have
decreased by 55-70 % since 2006-10. The data suggests that this is due
to an on-going long-lived response to the 2005-10 rifting episode, with
potential continued processes below the segment including a
lower-crustal viscous response and magma movement. Continued long-term
observations of surface deformation provide key constraints on
tectono-magmatic processes in Afar.