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

西藏是了解大陆碰撞大规模动力学的关键，但西藏地幔的很大一部分仅用相对低分辨率的技术进行了探测。 我们知道的足够多，可以说高原西部广大地区的平均地震波速度异常高，但我们缺乏足够的信息来区分大量可能的情况，以确定是什么导致了这些异常，以及它们在造山运动中可能扮演的角色。 例如，这些高波速（即，相对较冷的）块体，下沉到高原之下，并将邻近的地幔物质吸入其中，还是它们代表了俯冲的印度板块的前缘，从侧面提供了一个遥远的推动力？这个项目的主要目标是绘制这些高波速物质在西藏下地幔中的分布图，以区分这些相互竞争的假说。 将通过分析地震数据集来完成这一绘图，地震数据集是通过在西部高原部署宽带台站的多级准线性阵列来收集的，该阵列将低频到达的长周期（2-3年）记录与高频到达的短周期（1年）分段记录相结合。在处理中将使用主要基于到达时间层析成像和接收器功能分析的传统技术和最近开发的技术的组合。该项目将由3名PI和2名或更多的研究生和本科生在美国与来自中国的大量同事（科学家，技术人员，学生）合作进行，主要来自北京的中国地震局，也来自拉萨的西藏地震局。 此外，海得拉巴国家地球物理研究所的同事将通过在印度进行同步部署来扩大我们的覆盖范围。

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.