Crustal Structure Variation Across the Western Himalayas and Tibet
Amy Gilligan1,2, Keith F Priestley
1, Steven W Roecker
3, Vadim L Levin
4 and Shyam Sundar Rai
5, (1)University of Cambridge, Cambridge, United Kingdom, (2)Imperial College London, London, United Kingdom, (3)Rensselaer Polytechnic Inst, Earth & Environmental Sciences, Troy, United States, (4)Rutgers University, Earth and Planetary Sciences, Piscataway, United States, (5)National Geophys Res Instt, Hyderabad, India
Contact First Author: Amy Gilligan; amy.gilligan@abdn.ac.uk
Previously Published Material: Some of this work was presented at the AGU Fall meeting 2014 and a paper has just been submitted to JGR (awaiting reviewer asignment)
English Abstract:
We present new, high resolution, shear velocity models for the western Himalayas and West Tibet from the joint inversion of P receiver functions recorded using seismic stations from four arrays in this region and fundamental mode Rayleigh wave group velocity maps from 5-70s covering Central and Southern Asia. The Tibetan Plateau is a key locality in understanding large-scale continental dynamics. A large number of investigations has examined the structure and processes in eastern Tibet, however western Tibet remains relatively understudied. Previous studies in this region indicate that the western part of the Tibetan Plateau is not a simple extension of the eastern part. The areas covered by these arrays include the Karakoram and Altan-Tagh faults, and major terrane boundaries in West Tibet and the Himalayas.
We use the shear wave velocity models to obtain estimates of Moho depth. The Moho is deep (68-84km) throughout West Tibet. We do not observe significant steps within the Moho beneath West Tibet. A large step in Moho depth is observed at the Altyn-Tagh fault, where Moho depths are 20-30km shallower to the north of the fault compared to those to the south. Beneath the Lhasa Terrane and Tethyan Himalayas we observe a low velocity zone in the mid-crust. This feature is not interrupted by the Karakoram Fault, suggesting that the Karakoram Fault does not cut through the entire crust.
