Spatial analysis of neo-tectonics signatures in lower Subansiri sub-basin using morphometric parameters and Fuzzy-AHP

The present study investigates neo-tectonic signatures in the lower Subansiri River Sub-basin, a geo-dynamically active segment of the Eastern Himalayan Syntaxes. Remote sensing and GIS based morphometric analysis was conducted across twenty four selected indices such as Bifircation Ratio ( $$\:{\text{R}}_{\text{b}\text{m}}$$ ), Elongation ratio ( $$\:{\text{R}}_{\text{e}}$$ ), stream length gradient ( $$\:{\text{S}\text{l}}_{\text{g}}$$ ) etc., which were categorised into linear, areal, and relief aspects. Interpolation methods play a key role in geospatial analysis by predicting unknown spatial values from known data points, allowing the generation of continuous tectonic deformation maps. The study area is divided into uniform grids cell using GIS tools, and computing morphometric indices in each grid to generate thematic maps based on the defined parameters. Fuzzy AHP was employed to prioritize and integrate selected indices by ranking tectonic signatures through pairwise comparison and fuzzy logic by calibrating the real-world spatial conditions such as slope, elevation, relief and drainage density. The resulting prioritized weightages is unitless and classified into five categories ofneo-tectonic signatures: very low (3.8–4.7), low (4.7–5.1), medium (5.1–5.5), high (5.5–5.9) and very high (5.9–7.3). The majority of the lower Subansiri Sub basin is classified under high and very high weightage, reflecting significant neo-tectonic signatures. Ground-truth validation was employed to confirm the FAHP-derived weightage accurately. Accordingly, 207 field observation points were selected to verify the presence of neo-tectonic signatures within the study area. This research paper would provide a valuable framework and scope for geoscientists, geomorphologists, policymakers, and planners to develop context-specific, sustainable disaster risk reduction strategies for the region.