Morphotectonic segmentation and spatial variability of neotectonic activity along the Narmada―Son Fault, Western India: Remote sensing and GIS analysis

Morphotectonic analysis of landscape using remote sensing and GIS is an effective way of deducing the pattern and spatial variation of neotectonic activity along poorly investigated active faults. In this paper, we evaluate the neotectonic activity along a part of the seismically active but poorly understood Narmada-Son Fault (NSF), a more than 1000 km long ENE―WSW trending fault transecting through the central part of the Indian plate. The NSF in the study area is geomorphologically expressed as an ENE―WSW trending line of north facing scarps that delimit the rugged mountainous topography of the uplands to the south and the alluvial basin to the north which prominently slope away from the scarps. The scarps are developed in the south dipping basaltic flows belonging to the Deccan Trap Formation of the late Cretaceous―Eocene and continue westward into Tertiary rocks and further as a paleobank of the Narmada River. Field studies have revealed that the NSF in the study area is divisible into four morphotectonic segments (I to IV), which is attributed to the Tilakwada, Karjan, Madhumati and Rajpardi Faults cutting across the NSF. We characterize the neotectonic activity of the segments through DEM analysis, using geomorphic indices which include the mountain front sinuosity, hypsometric curves, hypsometric integral, asymmetry factor, stream length―gradient index and channel sinuosity. Interpretations of morphometric data are well supported by field data. Both the entire length of the NSF and the cross faults are found to be neotectonically active. We demonstrate that segment II has undergone the highest intensity of neotectonic activity followed by segments III, I and IV. This is corroborated by the highest elevation of scarps and the alluvial deposits, the deepest incision (∼40 m depth) and steep northward slope of the alluvial plain in segment II. We infer that the NSF is characterized by differential uplift in recent past which agrees with the high angle reverse faulting with oblique-slip movements along the cross faults.