Horizontal and Vertical Deformations of the Erta Ale Volcanic Segment in the Northern Rift Region of Ethiopia Using Sentinel-1 InSAR Time-Series Analysis with LiCSBAS

The Afar Triple Junction, where the Arabian, Nubian, and Somali plates diverge, is one of the most volcanically and tectonically active region on Earth. However, the east–west and vertical deformation field across the Erta Ale volcanic segment remains poorly constrained because previous InSAR studies have largely focused on individual volcanoes or line-of-sight deformation, limiting the characterization of horizontal and vertical ground motions across the entire segment. Here, we derive cumulative horizontal (east–west) and vertical displacements across the Erta Ale volcanic segment using a four-year (2022 to 2025) Sentinel-1 InSAR time series. Time-series analysis and two-dimensional decomposition were performed using the open-source LiCSBAS version 1.17 software to separate ascending and descending line-of-sight observations into horizontal and vertical displacement components. Deformation time series were generated for all six volcanoes to identify temporal trends and episodic deformation and to interpret the underlying magmatic and tectonic processes. The results reveal widespread subsidence across all volcanoes during the study period. Erta Ale and Alu Bagu exhibit westward horizontal motion, whereas Hayli Gubbi, Geda Ale, Alu Dalafilla, and Bora Ale show eastward displacement. The opposing horizontal motions produce an east–west separation of approximately 110 mm between Erta Ale and Hayli Gubbi, consistent with active rift extension. This 4 years intrusion-dominated separation and the long-term Red Sea spreading rate refer to different temporal scales and are therefore compared only qualitatively. The largest subsidence occurred at Erta Ale (−301.49 mm) and Hayli Gubbi (−271.37 mm), which is consistent with caldera-floor collapse and magma withdrawal associated with the mid-2025 dike intrusion event. The spatial variability of the horizontal and vertical deformation fields indicates the combined influence of shallow magmatic processes and regional tectonic extension. These results provide the first comprehensive characterization of east–west and vertical deformation components across the entire Erta Ale volcanic segment and offer new constraints on tectono-magmatic interactions and the ongoing evolution of the Afar Triple Junction.