Assessing neotectonic deformation and terrain evolution through geospatial morphometric techniques across the MBT zone, NW Himalaya

The transitional zone between the Sub-Himalaya and the Lesser Himalaya is delineated by the Main Boundary Thrust (MBT) to the north and the Himalayan Frontal Thrust (HFT) to the south. The MBT acts as a major topographic barrier that exerts significant control over longitudinal river valleys and sediment dispersal patterns. This region exhibits pronounced fluvial responses shaped by the interplay of tectonic activity and climatic processes. The present study addresses the need for detailed micro-scale morphometric analysis in this zone to better understand ongoing landscape deformation and neotectonic signatures. A multidisciplinary approach integrating geospatial morphometric techniques with field-based evidence has been employed to investigate terrain evolution. Quantitative morphometric assessments were conducted for 16 sub-basins within an active segment of the MBT, bounded by the Jakhan River to the east and the Giri River to the west. Dimensional changes driven by tectonic uplift and accelerated erosion/incision were evaluated using the hypsometric integral (HI), with most values falling below 0.50, indicating that the drainage basins are in an equilibrium stage. Basin shape (Bs) values range from 0.88 to 6.79, supporting the occurrence of accelerated erosional processes. The stream length gradient index (SL) exhibits values between 86 and 816, suggesting rapid uplift and incision. Similarly, computed values of the Chi (χ) coefficient (479–3706) and the steepness index (Ksn; 63–214) reflect differential erosion and strong tectonic control on drainage network evolution. The spatial distribution of tectonic deformation was statistically evaluated using a correlation matrix based on the Relative Index of Active Tectonics (RIAT). The results reveal that approximately 50.33% and 16.25% of the study area fall into high and moderate activity zones, respectively, which is corroborated by historical earthquake records and geomorphic evidence. Neotectonic signatures are preserved in the landscape as river terraces, displaced or tilted strata, V-shaped valleys, river offsets, knickpoints, hanging valleys, and channel migration along the strike of the MBT. These findings underscore the significant role of neotectonics in landform evolution and offer valuable insights for geohazard assessment and mitigation strategies in the rapidly developing foothill regions of the Himalaya.