Collaborative Research: Imaging the Upper Mantle Beneath the Western Tibetan Plateau

University Of Colorado At Boulder, Boulder CO

Investigators

Abstract

Tibet is key to understanding the large-scale dynamics of continental collisions, yet a substantial part of the mantle beneath Tibet has been probed only with relatively low-resolution techniques. We know enough to say that on average seismic wavespeeds in the vast western part of the plateau are unusually high, but we lack sufficient information to discriminate among a large number of plausible scenarios for what is causing these anomalies and what role they might play in the dynamics of mountain building. For example, are these high wavespeed (i.e., relatively cold) masses indigenous to the Tibetan lithosphere, sinking beneath the plateau and drawing adjacent mantle material into it, or do they represent the leading edge a subducting Indian plate that provides a distant push from the side? The primary objective of this project is to map the distribution of these high wavespeed masses in the upper mantle beneath Tibet in order to distinguish among these competing hypotheses. This mapping will be done by analyzing a seismological dataset gathered by deploying a multi-stage, quasi-linear array of broadband stations across the western plateau that combines long period (2-3 year) recording of lower frequency arrivals with shorter period (1 year) staged recording of higher frequency arrivals. A combination of traditional and recently developed techniques, based mostly on variations of arrival time tomography and receiver function analysis, will be used in the processing. This project will be carried out by 3 PIs and 2 or more graduate and undergraduate students in the US in collaboration with a substantial number of coworkers (scientists, technicians, students) from China, mostly from the Chinese Seismology Bureau in Beijing but also from the Tibetan Bureau of Seismology in Lhasa. Additionally, colleagues from the National Geophysical Research Institute in Hyderabad will extend our coverage across the border by carrying out a simultaneous deployment in India.