A.K. Awasthi

Use of digital elevation models and drainage patterns for locating active faults in the Upper Gangetic Plain, India

Twelve normal, active faults transverse to the regional Ganga and Yamuna longitudinal faults have been identified in the western part of the gently sloping Upper Gangetic Plain from the interpretation of digital elevation models (DEMs), prepared by manual digitization of spot heights from 1 : 50 000 scale topographic maps. High vertical exaggeration of these DEMs reveals artefactual morphostructures such as ‘cliffs’ and ‘significant breaks in slopes’ that are indicative of faults. Convergent drainage on the upthrown blocks, initiation of new streams on the downthrown blocks, offsetting of drainage and anomalous sinuosity of streams close to faults have provided additional corroborating evidence of the faults. Detailed field investigations indicate relatively steeper slopes close to the inferred faults than the adjoining areas. Erosion of the upthrown blocks and deposition of sediments on the downthrown blocks in the form of terminal fans under a semi‐arid climate formed features typical of many such faults.