Constraining ocean-mantle dynamics by improving shear-wave splitting with ocean bottom seismometers

横波分裂是一种提供有关地幔如何流动的信息的工具。然而，这项技术对于在占地球表面近70%的海底收集数据是困难的。该项目为海洋数据集实施了一种新的方法。关于什么驱动地幔流动以及岩浆如何到达火山的假说将得到检验。一名本科生将帮助进行数据分析，该方法将被广泛使用。剪切波分裂(SWS)的观测为岩石圈-软流圈系统的地球动力学提供了一阶约束。这个项目将调查三个科学问题。1)是地球表面板块的运动还是内部对流力驱动了大洋软流圈中的流动？2)地幔热柱是驱动构造板块下方的径向流动模式，还是被岩石圈-软流圈系统中的力捕获？3)大洋中脊下产生的熔体是通过剪切成带来分离的，还是熔体不与背景应变场相互作用？目前，使用海底地震仪进行SWS观测所涉及的挑战使解决这些问题变得困难。提出了一种方法来解决传统方法在海洋环境中面临的两个关键挑战--复杂的深度变化各向异性和低信噪比。在诺梅尔特遗址和加拉帕戈斯群岛的初步结果表明，与更传统的方法相比，有了重大改进。该方法将转换为Julia编程语言，供社区使用。这项提议实施的方法通过增加返回良好SWS结果的数据集的数量，增加了国内外海底地震仪实验的回报。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Shear-wave splitting is a tool that provides information about how the mantle flows. However, this technique is difficult for data collected on the seafloor which is nearly 70% of the Earth’s surface. This project implements a new approach for oceanic datasets. Hypotheses will be tested about what drives mantle flow and how magmas reach volcanoes. An undergraduate student will help with data analysis and the method will be released for wide use.Observations of shear-wave splitting (SWS) provide a first-order constraint on the geodynamics of the lithosphere-asthenosphere system. This project will investigate three science questions. 1) Do the motions of the plates on the Earth’s surface or internal convective forces drive flow in the oceanic asthenosphere? 2) Do mantle plumes drive a radial pattern of flow beneath tectonic plates, or are plumes captured by forces in the lithosphere-asthenosphere system? 3) Does the melt generated beneath mid-ocean ridges get segregated by shear into bands, or does the melt not interact with the background strain field? Addressing these questions at present is made difficult by the challenges involved in making SWS observations with ocean-bottom seismometers. A method is proposed to address two key challenges faced by traditional methods in oceanic environments – complex depth-varying anisotropy and low signal-to-noise ratios. Preliminary results at both the NoMelt site and Galapagos Archipelago show major improvements relative to more traditional approaches. The methodology will be converted to the Julia programming language for use by the community. The methodology implemented by this proposal increases the return from ocean-bottom seismometer experiments - both domestic and international - by increasing the number of datasets that return good SWS results.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.