Plate-Boundary Kinematics of the Afrera Linkage Zone (Afar) From InSAR and Seismicity

Studying the mechanisms of interaction between rift segments is key to understanding the kinematics of plate boundaries in continental rifts. However, the spatial and temporal evolution of deformation at rift linkage zones is rarely observed directly. Here, we combine InSAR data spanning 2005-2010 and 2014-2019 from ENVISAT and Sentinel-1 satellites, respectively, with local seismicity from the Afar rift to investigate the plate-boundary kinematics of the Afrera linkage zone, the junction between the Erta Ale and Tat Ali magmatic segments in Northern Afar (Ethiopia). We obtain time-series of cumulative InSAR Line-Of-Sight (LOS) displacements that show deformation is accommodated by a series of active en-echelon faults striking ~NS and characterized by normal slip associated with a left-lateral strike-slip component. Additionally, we observe spatial variation in fault behavior with stick-slip and creep. The faults in the center of the linkage zone behave primarily in a stick-slip mode (with abrupt fault displacements up to ~40 mm) and fault motions are associated with earthquakes of ML > 5. Conversely, faults at the edge of the linkage zone, near the magmatic segments, show creep and some stick-slip behavior (with cumulative LOS displacement up to ~30-40 mm over a ~5-year period) accompanied by low-level seismicity. Some of the creeping faults are also spatially associated with hydrothermal springs. We interpret that the temporal behavior of the faults in the linkage zone is controlled by the interplay between tectonic extension, high heat flows, and fluid circulation near the magmatic segments where creeping of some faults is favored.