EAR-PF: Investigating the role of the lithosphere-asthenosphere boundary through a 3D anisotropic velocity model of the Juan de Fuca plate

威廉·霍利博士获得了NSF EAR博士后奖学金，在哥伦比亚大学拉蒙特-多尔蒂地球天文台开展研究和教育计划。板块构造在很大程度上是我们理解地球长期演化的方式，并可能在使地球适合生命居住方面发挥作用。尽管它具有根本的重要性，但对驱动板块运动的因素的精确物理描述仍然不清楚。了解驱动力的一个关键组成部分是板块底部的区域，在那里它们与下面的对流地幔接触。PI将使用太平洋西北海岸附近洋底的地震数据来帮助描述板块下方这一关键区域的结构。通过推断地震波如何穿过地幔，并将这种结构与地表板块的运动进行比较，霍利博士将阐明地球上这些相互作用部分的物理和化学特征，并将有助于完善我们对板块构造的描述。教育计划涉及到纽约市及其周边地区的学校和社区组织，指导拉蒙特-多尔蒂地球天文台的研究生，并组织一个与板块构造相关的阅读小组。来自两个最大的海底地震仪阵列--卡斯卡迪亚倡议和布兰科变换实验--的数据将被用来建立北美太平洋西北部附近海洋地幔的三维各向异性速度模型。该项目将结合S到P接收函数对地震速度强梯度的敏感性和瑞利波对绝对地震速度的敏感性来创建横波速度模型。这一各向同性速度模型将是研究瑞雷波相速度与方位角关系的起点，从而得到地幔各向异性的三维模型。然后，霍利博士将从这个各向异性领域推断地幔流动，并将其与地表的板块运动学进行比较，最终细化板块大小与岩石圈-软流圈耦合的规模相关性。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。

Dr. William Hawley has been granted an NSF EAR postdoctoral fellowship to carry out research and educational plans at the Lamont-Doherty Earth Observatory of Columbia University. Plate tectonics is, in large measure, how we understand the long-term evolution of the planet Earth, and could play a role in making Earth habitable for life. Despite its fundamental importance, a precise physical description of what drives the motion of the plates remains unclear. A key component of understanding the driving forces is the region at the base of the plates, where they come into contact with the convecting mantle underneath. The PI will use seismic data from the ocean floor off the coast of the Pacific Northwest to help to characterize the structure of this critical zone beneath the plates. By inferring how seismic waves pass through the mantle, and comparing that structure with the motions of the plates on the surface, Dr. Hawley will shed light on the physics and chemistry of these interacting parts of the Earth, and will help refine our description of plate tectonics. The education plan involves outreach to schools and community organizations in and around New York City, mentoring graduate students at the Lamont-Doherty Earth Observatory, and organizing a reading group on issues related to plate tectonics. Data from two of the largest ocean bottom seismometer arrays, the Cascadia Initiative and the Blanco Transform Experiment, will be used to develop a 3D anisotropic velocity model of the oceanic mantle off the Pacific Northwest of North America. This project will combine the sensitivity of S-to-P receiver functions to strong gradients in seismic velocity and the sensitivity of Rayleigh waves to absolute seismic velocity to create a shear-wave velocity model. This isotropic velocity model will be the starting point to an investigation of the azimuthal dependence of Rayleigh wave phase velocities, resulting in a 3D model of anisotropy in the mantle. Dr. Hawley will then infer mantle flow from this anisotropic field, and compare that flow with plate kinematics on the surface, to ultimately refine the scale dependence of plate size on lithosphere-asthenosphere coupling.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.