Active transfer faulting in the NW Sub-Himalaya (India) observed by space-borne topographic analyses

Abstract

The results of surface morphology and InSAR analyses carried out along a NNE-SSW oriented (~7 km-long) transfer fault are presented. This structure actively accommodates differential motion across two blocks in the western Sub-Himalayan belt of India. Segmentation is most pronounced in this sector of the accretionary wedge, where minimal climatic variations and a three-fold sub-division (Kangra Renetrant-Nahan Salient-Dehradun Reentrant) are well recognized. Segmentation is here clearly elucidated by variation in surface topography, geologic structure and recorded seismicity over the last few decades. However, the transition from one segment to another is poorly documented and understood. This article primarily documents surface topography and drainage anomalies within the transition zone between the Kangra Reentrant and the Nahan Salient through the study of space imageries spanning nearly six-decades (i.e. early 1960's to present). Geomorphic observations and InSAR analyses demonstrate that the segmentation is largely governed by lateral variation in geological structure, deformation patterns and mechanical stratigraphy and accommodated by transverse movement along the transfer fault. It should be noted that transfer faults commonly represent a privileged pathway for the major drainage and therefore surface manifestations are rarely preserved, e.g. Yamuna Tear, Ganga Tear etc. A rare instance of preserved surface topography associated with the recent activity along the Sabilpur transfer fault at the transition between the Kangra Renetrant and the Nahan Salient is documented here. Our investigations demonstrate that the Sabilpur Active Fault (SAF) accommodates differential tectonic convergence between the two blocks predominantly by left-lateral strike-slip kinematics with a component of uplift related to thrusting at HFT.