Crustal Structure Along the Lawrencepur-Astor Profile in the Northwest Himalayas

Abstract

During the Pamir Himalayan project in the year 1975 seismic refraction and wide-angle reflection data were recorded along a 270 km long Lawrencepur-Astor (Sango Sar) profile in the northwest Himalayas. The profile starts in the Indus plains and crosses the Main Central Thrust (MCT), the Hazara Syntaxis, the Main Mantle Thrust (MMT) and ends to the east of Nanga Parbat. The seismic data, as published by Guerra et al. (1983), are reinterpreted using the travel-time ray inversion method of Zelt and Smith (1992) and the results of inversion are constrained in terms of parameter resolution and uncertainty estimation. The present model shows that the High Himalayan Crystallines (HHC, velocity 5.4 km s−1) overlie the Indian basement (velocity 5.8–6.0 km s−1). The crust consists of four layers of velocity 5.8–6.0, 6.2, 6.4 and 6.8 km s−1 followed by the upper mantle velocity of 8.2 km s−1 at a depth of about 60 km.