Abstract
The densely populated foothill zone of western Himalaya between the Beas river and the Chakki stream in and around Kangra is being critically examined by us considering the seismo-tectonic destructive potential of the 1905 (Mw 7.8) Kangra earthquake which has not been evaluated so far. We use Resourcesat 1: LISS III Ortho satellite imageries and field studies to qualitatively and quantitatively assess the active tectonic setup of the terrain. Quantitative morphotectonic analysis viz. hypsometric integral, drainage basin asymmetry, stream sinuosity index, ratio of valley floor width to valley height, stream length gradient index, basin shape index and mountain front sinuosity index are being evaluated on high resolution digital elevation model. The five sub-drainage basins of the Gandhiri stream, the Sukar stream and the Duhg stream of Kangra district of Himachal Pradesh, India are being morphotectonically analyzed. The value of hypsometric integral, drainage basin asymmetry, stream sinuosity index, ratio of valley floor width to valley height, stream length gradient index, basin shape index and mountain front sinuosity index reveal that the terrain is tectonically active. An active dextral strike slip fault with significant oblique slip component has been inferred and is being named as the Gandhiri Fault. This fault crosses all the five sub-drainage basins and results in multiple stream offsets. The Index of Relative Tectonic Activity (IRAT) has been established for different sub-drainage basins. The study reveals that the terrain near Gandhiri in Kangra district of Himachal Pradesh is seismo-tectonically active and proper building codes should be followed in construction activity.
Highlights
The Kangra (1905, Mw 7.8) earthquake, along with the Bihar-Nepal earthquake (1934, Mw 8.1), the Assam (1950, Mw 8.4) quake and other recent earthquakes has highlighted the importance of identification of active faults and their characterization so as to comprehend the quantum of seismic vulnerability of the densely populated Himalayan foothill region
Quantitative morphotectonic analysis viz. hypsometric integral, drainage basin asymmetry, stream sinuosity index, ratio of valley floor width to valley height, stream length gradient index, basin shape index and mountain front sinuosity index are being evaluated on high resolution digital elevation model
The main sections in this paper are geological setup, materials and methods, results comprising drainage basin, morphotectonic indices viz. hypsometric integral, drainage basin asymmetry, stream length gradient index, mountain front sinuosity index, stream sinuosity index, basin shape index, valley floor width to valley height ratio and field investigation followed by discussion and conclusion
Summary
The Kangra (1905, Mw 7.8) earthquake, along with the Bihar-Nepal earthquake (1934, Mw 8.1), the Assam (1950, Mw 8.4) quake and other recent earthquakes has highlighted the importance of identification of active faults and their characterization so as to comprehend the quantum of seismic vulnerability of the densely populated Himalayan foothill region. The tectonic activity in the Himalaya is due to the continuous movement of the Indian plate in the northward direction, at an average rate of 50 mm per year [1] This has made the foothill terrain a high stress and strain zone. The use of geomorphic indices such as the stream length gradient index [17], drainage basin asymmetry [18], hypsometric integral [19], ratio of valley floor width to valley height [20], drainage basin shape [20] [21] and mountain front sinuosity index [20] in active tectonic studies has been successfully demonstrated by numerous researchers including [4] [5] [20] [22] [23] [24] and others. The main sections in this paper are geological setup, materials and methods, results comprising drainage basin, morphotectonic indices viz. hypsometric integral, drainage basin asymmetry, stream length gradient index, mountain front sinuosity index, stream sinuosity index, basin shape index, valley floor width to valley height ratio and field investigation followed by discussion and conclusion
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