Oblique convergence in the Himalayas of western Nepal deduced from preliminary results of GPS measurements

A GPS network consisting of 29 sites was installed in central and western N epal, with measurements taken in 1995 and partial remeasurements in 1997. D ata suggest 15 +/- 5 mm/yr of N180 degrees convergence between the Higher H imalayas and India, a result that is consistent with NS shortening across t he arcuate shape of the Nepalese Himalayas and an oblique underthrusting of the Indian crust below the High Himalayas of western Nepal. A 4 +/- 3 mm/y ear E-W extension and deviation of the principal shortening axes are inferr ed east of 83 degrees E, where Quaternary faults (Darma-Bari Gad fault syst em and Thakkhola graben) delineate a crustal wedge. This wedge is located o n the SE projection of the Karakorum fault and may segment the Himalayan th rust belt. The convergence between the outer belt of western Nepal and Indi a is less than 3 mm/yr, an attenuation consistent with creep on a dislocati on locked beneath the Lesser Himalayas, A preliminary model suggests that t his N120 degrees E striking dislocation is affected by a 19 mm/yr thrust co mponent and a 7 mm/yr right lateral component.