Active Deformation along the Hinna Fault in Uttarkashi Region of Garhwal Himalaya

The Hinna fault, in the meizoseismal region of 1991 Uttarkashi earthquake, has been observed as a N-S trending lineament in the satellite imagery and aerial photographs. The stratigraphic and structural expression of the fault has been studied in soft sediments to assess the activity of fault. The Hinna fault occurs as a principal Low-Angle reverse fault dipping towards east and has not ruptured the surface in the trench section. The correlative stratigraphic horizons occur on both side of the main fault with the beds occurring as monoclinal drape over the principal fault. The hanging wall shows warping with development of extensional faults. Extensional faults are produced by the bending moment of strata. The faults also displace the liquefaction features in the soft sediments suggesting their formation prior to faulting event. The tips of the principal reverse fault and the related secondary faults are covered by -3 in thick gravel unit. This suggests that the fault was active prior to the deposition of gravel unit and was not ruptured during 1991-Uttarkashi earthquake.