Evidence for distributed transpressional deformation and seismic hazard implications from the 2025 Mw 6.0 Asadabad- Kunar earthquake, Eastern Afghanistan

Abstract

The Hindu Kush region of eastern Afghanistan is an active intracontinental deformation zone where ongoing India-Eurasia convergence is accommodated through interacting strike-slip, reverse and transpressional fault systems. On 31st August 2025, an Mw 6.0 earthquake occurred within the Kunar-Spin Ghar fault system, causing widespread infrastructure damage, landslides and surface deformation across a rugged and poorly accessible mountainous region. Field reconnaissance at accessible sites documented structural damage, ground cracks, slope failures, rock avalanches and newly emerged springs along the Kunar River valley. To characterize the earthquake-period deformation and examine its spatial relationship with the mapped fault network, we integrated field observations with Persistent Scatterer Interferometric Synthetic Aperture Radar (PSInSAR) time-series analysis of Sentinel-1 A data acquired between April and October 2025. The ascending and descending line-of-sight velocity fields reveal a laterally continuous deformation pattern extending for several tens of kilometres along strike. Decomposition into east-west and vertical components indicates dominant horizontal motion accompanied by broader and spatially variable uplift-subsidence patterns. Swath-profile analysis shows that the strongest east-west velocity gradients occur south of the mapped Kunar Fault and within or adjacent to the Spin Ghar mountain-front structural corridor. These observations indicate that the earthquake-period deformation signal was distributed across multiple interacting structures rather than confined to a single mapped fault trace. The observed pattern is consistent with distributed transpressional deformation within the broader Kunar-Spin Ghar system and suggests that seismic-hazard assessments based only on mapped fault traces may underestimate the width of the active deformation corridor and the spatial extent of associated ground deformation and secondary hazards.