Imaging Upper-Mantle Structure under USArray using Long - Period Reflection Seismology

这个项目将研究美国地下800公里（500英里）深处的地幔结构。研究人员将使用USArray项目提供的数据，该项目在7年的时间里在美国各地部署了约2000个地震站。科学家们将分析来自遥远地震的记录，这种地震被称为远震，它包含了反射上地幔层和其他特征的地震剪切波。该项目采用类似于石油行业解决地壳分层和油藏问题的方法，将提供美国邻近地区（即不包括阿拉斯加和夏威夷）地下深处的3D图像。与大多数现有研究相比，这些分析应该具有更高的分辨率，并将有助于解决有关北美大陆组成和构造演化的悬而未决的问题。该项目将支持一名博士后研究员和一名本科生暑期学生，他们来自一个旨在增加地球和海洋科学职业道路学生多样性的项目。本研究将使用反射地震学方法对USArray记录的上部s波混响进行成像，对美国邻近地区的上地幔结构进行成像。产品将包括410公里和660公里地幔不连续性的新地图，以及在许多地区看到的较浅的区域上地幔反射物，以及古俯冲法拉龙板块的反射物。研究结果将有助于将法拉龙俯冲作用与美国西部现在和过去的构造联系起来，并阐明岩石圈-软流圈边界在北美克拉通深部的作用。提高对上地幔结构急剧变化的分辨率将有助于解决这些问题以及其他有关地幔成分和动力学的问题。由于这些结果对阻抗对比（地震速度和密度）很敏感，因此它们为地震接收器功能研究提供了有用的补充，地震接收器功能研究主要对S速度跳变敏感。初步结果表明，该方法提供了一种令人兴奋的探测上地幔结构的新方法，特别是当与其他模型和数据约束相结合时。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This project will study the structure of the mantle below the United States at depths up to 800 kilometers (500 miles). Researchers will use data provided by the USArray project, which deployed ~2000 seismic stations across the United States over a 7-year period. Scientists will analyze records from distant earthquakes, called teleseisms, which contain seismic shear waves that reflect off layers and other features in the upper-mantle. By applying methods similar to those used by the oil industry to resolve crustal layering and oil reservoirs, this project will provide 3D images of the deep subsurface below the contiguous United States (i.e., excluding Alaska and Hawaii). The analyses should have superior resolution compared to most existing studies and will help resolve outstanding questions regarding the composition and tectonic evolution of the North American continent. The project will support a postdoctoral researcher and an undergraduate summer student from a program designed to increase the diversity of students in Earth and ocean sciences career paths.This research will image upper-mantle structure under the contiguous United States using reflection-seismology methods applied to topside S-wave reverberations recorded by USArray. Products will include new maps of the 410- and 660-km mantle discontinuities, as well as shallower regional upper-mantle reflectors seen in many areas, and reflections off the ancient subducting Farallon slab. The results should help relate Farallon subduction to current and past tectonics in the western United States and clarify the role of the lithosphere-asthenosphere boundary with respect to the deep cratonic root of North America. Improved resolution of sharp changes in upper-mantle structure will help address these and other issues regarding mantle composition and dynamics. Because these results are sensitive to the impedance contrast (seismic velocity and density), they provide a useful complement to seismic receiver-function studies, which are primarily sensitive to the S velocity jump alone. Preliminary results suggest the proposed method provides an exciting new way to probe upper-mantle structure, particularly when integrated with other models and data constraints.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.