Aseismic Slip on the Ilyak Strike‐Slip Fault (Tajikistan) and Active Fault and Landslide Hazards in and Around the Tajik Basin Revealed by InSAR

Abstract The Ilyak fault in Tajikistan is an E‐W striking strike‐slip fault, which forms the northern boundary of the actively deforming Tajik Basin fold and thrust belt. Determining the activity of the Ilyak fault is important for understanding the hazard to the nearby capital city of Dushanbe, and more generally in assessing the role of lithology in controlling fault behavior. Using a bespoke Multi‐Temporal InSAR approach with 5 years of Sentinel‐1 satellite radar acquisitions, we produce regional surface velocity maps with a horizontal spatial resolution of 130 m and numerical uncertainties below 1 mm/yr. Our rate maps reveal previously unrecognized details of creep, fault structure, and slip partitioning. We document creep on the Ilyak fault with a right‐lateral rate of 8.1–8.7 mm/yr in the east reducing to 4.2–4.5 mm/yr in the west, as slip is progressively transferred to adjacent folds and thrusts in the Tajik Basin. Creep on the Ilyak fault and adjacent thrusts appears to be controlled by lithology, in particular the presence of evaporite‐rich layers. Nonetheless, moderate earthquakes within the basement beneath the Ilyak fault, including a destructive M5.5 event in 1989, suggest potential earthquake hazards from deeper crustal layers. Using high‐resolution Digital Elevation Models derived from optical stereo satellite data we document fault scarps north of the Ilyak fault, which may constitute an additional source of hazard. Filtered velocity maps also show evidence of soil creep and active, slow‐moving landslides across the basin and in the mountains, constituting another hazard to local communities and infrastructure.