Koyna-Warna Shallow Seismic Region, India: Is there Any Geomorphic Expression of Active Tectonics?
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Koyna-Warna Shallow Seismic Region, India: Is there Any Geomorphic Expression of Active Tectonics? Sumit Das Department of Geography, Savitribai Phule Pune University, Pune - 411007, India Email: [email protected]
ABSTRACT This study investigates the geomorphic expression of tectonic control in Koyna-Warna shallow seismic region, lying on Deccan Flood Basalt in India, by examining longitudinal profiles and morphometric parameters by using Digital Elevation Model (DEM) and constrained field examinations. A total of 60 sub-catchments have been analyzed to comprehend the relative tectonic control in the study area. Sub-catchments within the study area depict channel disequilibrium through stream length-gradient index (SL) and normalized steepness index (ksn) which are ascribed to numerous transient knickpoints along the drainage profiles. The integrated analysis based on six different morphometric parameters (i.e. basin asymmetry, hypsometric integral, stream-length gradient index, valley width-to-height ratio, elongation ratio, and average normalized steepness index) demonstrates two explicit examples of high tectonics in Koyna-Warna region, are (a) between the Koyna Rift Fault Zone (KRFZ) and Patan Fault (PF); and (b) upstream region of left-hand tributaries of the Koyna river. INTRODUCTION Geomorphology of the landscape epitomizes the equilibrium between mechanisms that create and destroy topographic relief through uplift and erosion (D’Arcy and Whittaker, 2014). Fluvial landscape is one of the most sensitive geomorphic features that capture the combined effects of variations in lithology, climate and tectonics (Schumn, 1986). In high relief terrains, active tectonics during the recent geological period can be reflected through fluvial incision and sediment yield; diversions of stream channels, creation of hanging tributaries and so forth (Bull and McFadden, 1977; Keller et al., 2000; Molin et al., 2004; Bull, 2007; Peters and van Balen, 2007; Kale and Shejwalkar, 2008; Pérez-Peña et al., 2010; Ambili and Narayana, 2014; Kale et al., 2014a). The rivers in equilibrium exhibit a concave upward profile, where lower-order streams show higher gradients in comparison to that of with higher-order streams (Keller and Pinter, 2002). Deflection from this geometry within a longitudinal profile occur either due to variations in the bedrock lithology or may (with knickpoint development, etc.) reflect active tectonic influence on the profile development. Quantitative measurements of the landscape can deliver substantial information about the geomorphic evolution and degree of tectonic activity during recent geological periods. Geomorphic indices such as hypsometric curve and integral, stream-length gradient index, valley floor width-to-height ratio, channel steepness and concavity, basin shape, and asymmetry factor are highly convenient tools to understand the active tectonics as these indices deliver insights into specific sites which are rapidly adjusting to the variable tectonic deformation (Keller, 1986; Kell
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