Distributed Transpressional Deformation in Eastern Afghanistan: PSI Observations of the 2025 Mw 6.0 Kunar Earthquake

Abstract The Hindu Kush region in eastern Afghanistan is an intracontinental deformation zone resulting from India-Eurasia convergence that accommodates crustal strain through distributed strike-slip and thrust faulting processes. On August 31st, 2025, a magnitude 6.0 earthquake ruptured the Kunar-Nangarhar segment of eastern Afghanistan, causing extensive infrastructure damage, landslides, and ground deformation in difficult-to-reach regions with rugged topography. Nonetheless, reconnaissance in easily accessible parts revealed surface rupture, rock avalanches, and slope failures primarily localized in the valley of the Kunar river. In order to analyse the deformation pattern and identify potential fault planes, here we combine geomorphic observations with PS-InSAR time-series analysis of Sentinel-1A data covering the period of April to October 2025. Time-series InSAR reveals spatially coherent deformation extending tens of kilometres along strike. Ascending and descending PS-InSAR LOS velocity maps reveal an evident polarity change along the active fault zone, while decomposing the motion vector into east-west and vertical components indicates predominant horizontal deformation with localized uplift. The largest horizontal strain rate gradient is parallel with the range-bounding structures of the Spin Ghar, rather than being aligned with one particular mapped strand of the Kunar fault system. Additionally, vertical motion measurements show localized uplift in the mountain front, and subsidence within the intermountain basin area. All in all, our results point to the possibility of distributed deformation, with the strain being transferred across several active structures, rather than along a single major fault. Our findings imply that seismic hazard in the region of eastern Afghanistan may have been underestimated, since the assessments based on the mapping of individual fault traces may prove inadequate.