The crustal structure of the Hindukush region

Abstract

The crustal structure beneath the Hindikush and adjoining region have been investigated using body wave data of near earthquakes. The crustal structure in the region has been found to consist of three layers: viz., granitic 1, granitic 2 and basaltic layers. The velocities in the three layers respectively of longitudinal and transverse seismic waves have been obtained as 5.32±0.03, 5.64±0.01 and 6.43±0.01 km/sec; and 3.28±0.002, 3.53±0.003 and 3.93±0.001 km/sec, respectively. The average thickness of the three layers has been computed as 17.5±5.5, 15.9±4.1 and 16.7±2.7 km respectively, making the average thickness of the crust as 50±11.9 km. It has been observed that the Mohorovicic discontinuity dips at an angle of 2⁰ from north to south between Taskent and Quetta along 68⁰E  (profile AB, Fig 1). A dip of only 22` has been observed for the discontinuity between the points 37⁰N, 68⁰E and 44⁰N , 81⁰E (profile CD, Fig. 1). The thickness of the crust beneath Quetta has been obtained as 62±15.8 km.