ASSESSMENT OF GEOMORPHIC RESPONSE AND LANDFORM EVOLUTION DUE TO ACTIVE TECTONICS AT HIMALAYAN FRONTAL THRUST

摘要

The evidences of crustal deformation and its manifestation on surface geomorphology in the recent past (1972-2003) has been reported from a seismically active Himalayan Frontal Thrust (HFT) zone at Dehradun reentrant, India by comparative analysis of Landsat images of 1972 and IRS-PAN and LISS-III images of 2003. Terrain analysis using high resolution DEM from Cartosat-1 stereo data aided by Differential GPS based Ground Control Points (GCPs) and SRTM data also revealed tectonic influence on landform development. The eastward shifting of rivers, reversal of the drainage direction, straightening of the course, shifting of the water divide, development of close meanders, and uneven bank erosion point towards strong tectonic influence in landform development at the frontal region. Geomorphic indices related to asymmetry, sinuosity index, transverse topographic symmetry index and hypsometric integral curve have been used for finding correlation between basin parameters and active tectonics and provide clues towards conceptual model for landform development at active mountain front. Based on relict mountain front identification, migration of mountain front has been inferred in last 1.5-1.7 MY assuming that movement along HFT resulted in development of first mountain front due to upliftment of the hanging wall block consisting of Upper and Middle Siwaliks. The study also throws light on possibility of development of new faults leading to upliftment and complimentary subsidence zones at the frontal region.