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The present study area represents one of the active segments of the frontal part of the Arunachal Himalaya. The major structural boundaries traversing the area are the Main Boundary Thrust (MBT) and the Himalayan Frontal Thrust (HFT) and other local faults are tectonically active, as evident from the landforms that evolved in the fault zones. Strath terraces and uplift fluvial terraces are observed in the hanging‐wall block of the HFT and MBT, and along the HFT straight to curvilinear mountain fronts are observed. Normal faults both transverse and parallel to the strike of HFT are observed in the hanging‐wall block of the HFT. West of Pasighat the sub‐Himalaya terrain resembles a duplex, where there is gradual rise in elevation from the Brahmaputra Plain to the low‐lying hills of the sub‐Himalayan and sudden rise in elevation across the MBT. Drainage aligning to the bedrock structures and stream migrations are observed in the fault zones. Along the MBT, the sub‐Himalayan rocks are thrusted over either by quartzite or black carbonaceous shales, in some sections the MBT is behaving as a back‐thrust that dips towards the south. The MBT has also been displaced by almost N–S‐trending transverse faults where highly sheared bedrocks are also observed. Tilting of Quaternary fluvial deposits are observed in the hanging‐wall blocks of intraformational thrusts at two locations. Signatures of paleoseismic activities in the form of various soft‐sediment deformational structures are observed in Quaternary deposits in the HFT zone and also in the hanging‐wall block of the MBT. To determine the deformation and strain rate accumulation, we have re‐analysed the available GNSS results of the area, which indicate a deformation rate of up to 16 mm/year in the vicinity of the Pasighat region. The GPS‐derived deformation rates are well corroborated with the existing results of peak ground acceleration (PGA) anomalies. The component–wise motion indicates higher fault perpendicular motion in this part, which reveals an accumulation of more strain along the major Himalayan faults. [ABSTRACT FROM AUTHOR]

In the present study, an attempt has been made to delineate anomalous morphotectonic elements in the lower valley of Ravi and Beas rivers of the NW Himalaya by utilising the digital elevation model (DEM) as well as GIS based approach. We selected the surrounding areas of both the rivers as these have developed tectonically formed lakes such as Khajjiar and Rewalsar in late Holocene and lie in the north and south of Kangra re-entrant structure. We generated topographic swath profiles, calculated normalized steepness index (ksn) and hypsometric integral (HI) and conducted lineament analysis and finally correlated the obtained data set with the contemporaneous seismicity to decode the tectonic activity in the region. Based on the calculated HI for both the areas as 0.45 and 0.47, we infer that there are anomalous changes in the steepness, pointing to the presence of active tectonics. By using lineament analysis, geological information and the quantitative analysis, we identified lineaments parallel and oblique to the regional strike of the NW Himalaya, indicating the area as tectonically active. The lower steepness values along the inferred lineaments suggest the presence of strike-slip features that absorb the oblique convergence of the Indian plate with Eurasia. The GPS based additional observations suggest significant amount of deformation, showing higher deformation rate in the vicinity of the Khajjiar as compared to the Rewalsar locality. Based on remote sensing and GIS based approaches, we conclude that the study area is tectonically very active, hence there is need of careful examination of identified structures and impact on the development of infrastructure and seismic hazard assessment of the western Himalaya. [Display omitted] • Pull apart Sundernagar basin and Rewalsar lake were studied. • KJR exhibits higher steepness than the RWL. • Lithology does not affect steepnessand HI distribution locally. • Lineaments with seismicity supports their tectonic nature. [ABSTRACT FROM AUTHOR]