Geomorphic signatures of the neotectonic activity in Haridwar-Kotdwar region, Northwestern Himalaya, India

In this study, we investigate the ongoing crustal deformation in the Haridwar-Kotdwar piedmont zone of the Northwestern Himalaya, India. The Himalayan mountain front has been actively deforming along the Himalayan Frontal Thrust (HFT) which marks the conjunction between the Siwalik hills and the Indo-Gangetic Plains. We report NNE-SSW trending left lateral strike-slip fault towards the west of the study area namely Haridwar Fault (HF) and it offsets the HFT sinistrally by ~ 9 Km. Using the satellite imagery (Cartosat-1 stereo pairs) flat-lying uplifted river terrace have been identified, which is at an elevation of ~80 m from the flood plain of Mitthawali River. Along with uplifted terraces, the HF offsets various structural features, the rivers flowing across it and manifests itself as a series of scarps and slope breaks visible in the satellite imagery. The Khoh River Fault (KRF) trends N-S and offsets HFT dextrally by ~12 Km, this controls the course of the Khoh River and forms a lateral ramp perpendicular to HFT. The KRF manifests itself geomorphically as uplifted terraces at an elevation of ~50 m from the flood plain of the Khoh River which is conspicuous in the DEM and the Cartosat-1 imagery of the area. The Haridwar-Kotdwar piedmont zone has been surrounded in the north by HFT, in the south by Najibabad Fault (NF), towards east by KRF and the western margin has been dissected by HF. The KRF and HF show signatures of neotectonic activity and offsets HFT at two locations forming two ramps in the region. The piedmont zone has been showing signatures of upwarping which causes sudden migration of the rivers flowing into the piedmont zone on a decadal scale, mainly caused by an E-W trending NF. NF is a blind fault and manifests itself geomorphically by series of knee turn bending of the rivers in the study area. The deformation caused by NF has been comprehended using the satellite imageries and Gradient Length Anomalies (GLA). The GLA results show signatures of upliftment in the piedmont zone along the NF. The Haridwar-Kotdwar piedmont zone is surrounded by neotectonically active faults from four sides, making this block a potential seismic hazard in near future.