Collaborative Research: Lithosphere-scale anisotropic imaging across the Eastern North American Margin's ocean-continent transition

大陆形成和随后分裂形成海洋的循环是板块构造的一个重要方面，也是塑造地球的基本过程之一。然而，有几个大陆裂谷的细节仍然困扰着我们。断裂边缘，例如包括整个美国东海岸的边缘，代表了大陆地壳和海洋地壳之间的接触，在分裂期间和之后形成（在这种情况下，大西洋随着非洲的离开而形成）。这些边缘保留了导致大陆分裂、与大陆分裂同时发生以及随后发生的过程的记录。该项目将利用现有的陆上和海上地震数据，详细研究产生现代美国东部的变形，其结果将有助于评估当代灾害和风险沿着边缘。该项目支持在圣巴巴拉的加州大学培训一名研究生，并在亚利桑那大学培训至少一名本科生。它还支持对北卡罗来纳州几所高中的外联活动，这些高中拥有记录分析中使用的地震数据的地震仪器。 该项目旨在阐明与北美东部被动裂谷边缘（ENAM）相关的结构，演化和持续动力学的两个基本科学问题：1）海洋-大陆过渡的岩石圈从上到下的结构是什么？2)被动大陆边缘内部和向海方向的变形历史是怎样的？现今的地幔流动是如何被大陆边缘的结构所控制的？深度约束的三维各向异性速度模型将产生从地壳到岩石圈-软流圈边界（LAB）以下的ENAM。通过依次采用不同的成像技术，我们将建立一套互补的模型：a）由环境噪声和地震面波反演的三维各向同性剪切速度模型：B）利用对壳幔不连续性敏感的S-p和P-s接收函数联合反演的频散曲线的一维高分辨率速度剖面; c）使用表面波层析成像作为起始模型的3-D有限频率体波方位各向异性层析成像。这些模型将被共同解释，以完善地壳厚度和LAB性质的估计，在整个边缘的背景下，地球动力学裂谷模型，以及了解变形流在裂谷和边缘成熟到今天。这一奖项反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的影响审查标准的支持。

The cycle of continent formation and subsequent breakup to build oceans is an essential aspect of plate tectonics and is one of the fundamental processes that shape the planet. Yet, there are several details of continental rifting that continue to elude us. Rifted margins, such as that which comprises the entire east coast of the United States, represent the contact between continental crust and oceanic crust that is formed during, and after, the breakup (in this case, the Atlantic Ocean formed as Africa moved away). These margins retain a record of the processes that led up to, coincided with, and followed continental breakup. This project will utilize existing onshore and offshore seismic data to study in detail the deformation that produced the modern day eastern U.S. The results will aid in assessing contemporary hazard and risks along the margin. This project supports the training of a graduate student at the University of California at Santa Barbara and at least one undergraduate student at the University of Arizona. It also supports outreach activities to several high schools in North Carolina that hosted seismic instruments that recorded earthquake data used in the analyses. This project aims to shed light on two fundamental scientific questions related to the structure, evolution, and on-going dynamics associated with the eastern North American passive rift margin (ENAM): 1) What is the structure of the lithosphere from top to bottom across the ocean-continent transition and how was it shaped by rifting processes? 2) What is the history of deformation both within and seaward of the passive margin, and how is present-day mantle flow controlled by the margin's structure? Depth-constrained 3-D anisotropic velocity models will be produced of the ENAM from crust to below the lithosphere-asthenosphere boundary (LAB). By employing different imaging techniques in sequence, we will create a suite of complementary models: a) 3-D isotropic shear velocity model from inversion of ambient noise and earthquake-generated surface waves; b) 1-D high-resolution velocity profiles using dispersion curves inverted jointly with S-p and P-s receiver functions sensitive to crust and mantle discontinuities; c) 3-D finite-frequency body-wave azimuthal anisotropy tomography using the surface wave tomography as a starting model. These models will be jointly interpreted to refine estimates of crustal thickness and LAB character across the margin in the context of geodynamical rifting models, as well as to understand deformational flow during rifting and margin maturation to the present day.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.