Survey of Active Tectonics in Western Afghanistan Using Geomorphic Indices: A Case Study of the Northern Herat Basins

The ongoing convergence of the Eurasian, Helmand, and Iranian tectonic plates has positioned Afghanistan within a highly active tectonic zone, with spatial variations in deformation linked to regional plate dynamics. Western Afghanistan's Herat region, situated along the east-west trending Herat-Harirod fault system, exemplifies such dynamic activity. Rapid urbanization in this area underscores the critical need for robust neotectonics assessments to inform sustainable development. This study integrates multispectral satellite imagery (Landsat TM/ETM+, 30m DEM), geospatial analysis (ArcGIS), and geomorphometric techniques to evaluate tectonic potential. Key indices including valley floor width-to-height ratio (Vf), drainage basin shape (Bs), mountain front sinuosity (Smf), topographic basin asymmetry (T), drainage basin asymmetry (Af), and stream channel sinuosity (S) were computed to quantify tectonic activity. Field observations of Quaternary landforms, such as fault-induced river displacements, deflected drainage networks, and the juxtaposition of young and ancient alluvial fans, further corroborated remote sensing findings. The synthesized Landscape Activity Index (Lat), derived from these metrics, classifies the region as Class 1 (highest activity) within the tectonic activity spectrum. Results highlight active deformation, evidenced by deep V-shaped valleys, strike-slip faulting, and recurrent alluvial fan development. This study emphasizes the imperative of incorporating tectonic hazard assessments into urban planning frameworks to mitigate risks to infrastructure and communities. Proactive measures are essential to enhance resilience in this tectonically dynamic and rapidly developing region.