Geodetic constraints on slip rate on the Karakoram fault and its role in the Himalayan arc deformation

Abstract

The evolution of the >1000 km long Karakoram fault along the southwestern margin of the Tibetan plateau and its role in Himalayan arc deformation is debated extensively. We report new results of continuous GPS measurements along a >300 km length of the Karakoram fault and suggest that the fault in the Nubra valley (K2 segment of the northern Karakoram fault) is inactive while that in the Bangong Chaxikang region (the southern Karakoram fault), slips at a rate of 1.6–3.2 mm/year. The low slip rate on the southern segment and no slip on the northern segment of the Karakoram fault support the model in which the Karakoram fault is considered a transient feature (and not a lithospheric scale fault) in the Himalayan arc deformation, that acted as transfer structure linking thrusts in the Pamir and western Tibet. Once the Longmu Co Gozha Co fault system (a part of the Altyn Tagh fault) developed in the late Pliocene and impinged on the Karakoram fault, the northern segment of the Karakoram fault became inactive. Further, our modelling of GPS measurements indicates a locking depth of ∼12–15 km for the southern Karakoram fault. Although, because of low fault slip and uncertainty in the measurements it is not well constrained, the lack of historical and instrumental earthquakes of large magnitude implies that the southern part of the Karakoram fault has been accumulating deformation for several centuries, probably confirms that the southern Karakoram fault has been accumulating strain for several centuries.