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

该项目将研究美国下方深达800公里(500英里)的地幔结构。研究人员将使用美国阵列项目提供的数据，该项目在7年内在美国各地部署了约2000个地震台站。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，其中包含反射出地层和上地幔其他特征的地震横波。通过应用与石油行业用于解决地壳分层和油层的方法类似的方法，该项目将提供毗邻的美国(即不包括阿拉斯加和夏威夷)地下深层的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的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人员和一名本科生暑期学生，该项目旨在增加地球和海洋科学专业学生职业生涯的多样性。这项研究将使用反射地震学方法成像毗邻的美国下面的上地幔结构，该方法应用于美国阵列记录的顶部S波混响。产品将包括410公里和660公里地幔不连续的新地图，以及在许多地区看到的较浅的区域上地幔反射体，以及来自古老俯冲法拉隆板块的反射。这些结果应该有助于将法拉隆俯冲作用与美国西部现在和过去的构造联系起来，并澄清岩石圈-软流圈边界相对于北美深克拉通根部的作用。提高对上地幔结构急剧变化的分辨率将有助于解决这些和其他有关地幔成分和动力学的问题。因为这些结果对阻抗对比度(地震速度和密度)很敏感，所以它们为地震接收函数研究提供了有用的补充，而地震接收函数研究主要只对S速度跃变敏感。初步结果表明，提出的方法提供了一种令人兴奋的新方法来探索上地幔结构，特别是在与其他模型和数据约束相结合的情况下。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。

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.