Investigating Lithospheric Heterogeneity of the North American Craton with Multiple Seismological Methods

地球大陆岩石圈的相对稳定的核心，被称为“稳定”的构造特征，通常对破坏和回收具有弹性。这种弹性并不意味着岩石不会因构造过程而变形。在全球范围内，在盆地内部，有大量的局部沉降、隆起和破碎，形成盆地、山脉和裂谷。这些构造特征也是重要的矿产和石油资源以及地震的所在地。尽管古地磁子及其相关的构造特征在科学和社会上具有重要意义，但这些特征是如何形成的，以及古地磁子如何在漫长的（数十亿年）构造演化历史中幸存下来，目前还不清楚。该项目将通过构建多种类型的地震模型来研究北美大陆中部的地震特征。这些地震模型将提供制约的构造机制，修改了北美岩石圈。该项目将支持研究生和本科生进行地震数据分析和解释。通过与普渡大学的外联办公室合作，该项目将制作一个关于美国中西部地质和构造的教育视频系列，一般来说，火山岩被认为是“稳定的”构造特征，一般可以承受破坏和回收利用。最近的地球物理成像、地质调查和地球动力学模型的观测结果支持了岩石圈的显著结构和成分变化，这一想法越来越受到质疑。该项目将使用多种方法构建北美板块内部的多类型地震模型，包括全波环境噪声层析成像、平面波偏移接收器函数和地震各向异性分析。在新的结构约束下，该项目将系统地评估四个先前提出的岩石圈演化的端元方案。这个项目的结果将揭示地球科学中的几个基本问题：1）什么是修改稳定的质子的过程？2)为什么以及如何在漫长的地质构造事件中幸存下来？（3）先存结构对后期变形的影响？该项目的成果也对研究大陆演化的地球科学学科（如地震学、地质学、地貌学、岩石学和地球动力学建模）产生了重要影响。该奖项反映了NSF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。

The relatively stable cores of the Earth’s continental lithosphere, referred to as cratons, are considered “stable” tectonic features that are generally resilient to destruction and recycling. This resilience does not mean that cratons are not deformed by tectonic proceses. Globally, within the interior of cratons, there are a large number of local subsidence, uplifts, and breakups that form basins, mountains, and rifts. These tectonic features are also localities of important mineral and petroleum resources, as well as earthquakes. Despite the scientific and societal importance of cratons and their associated tectonic features, it is unclear how these features form and how cratons survive the long (billions of years) history of tectonic evolution. This project will examine the seismic signatures within the North American midcontinent by constructing multiple types of seismic models. These seismic models will provide constraints on the tectonic mechanisms that have modified the North American cratonic lithosphere. This project will support graduate and undergraduate students in seismic data analysis and interpretations. By working with the outreach office at Purdue University, this project will create an educational video series on the geology and tectonics of the Midwest U.S., which will be accessible to the public.Cratons are normally considered “stable” tectonic features generally resilient to destruction and recycling. This thought has become increasingly questionable with recent observations from geophysical imaging, geological surveys, and geodynamic modeling that support significant structural and compositional modifications of the cratonic lithosphere. This project will construct multi-type seismic models of the North American cratonic interior with multiple methods, including full-wave ambient noise tomography, plan-wave migration receiver functions, and seismic anisotropy analysis. With the new structural constraints, this project will systematically evaluate four previously proposed end-member scenarios for the evolution of the cratonic lithosphere. The result of this project will shed light on several fundamental questions in Earth sciences: 1) what are the processes that modify stable cratons? 2) why and how did cratons survive the long history of tectonic events? And 3) how do pre-existing structures influence later deformation? The outcome of this project also has important implications across geoscience disciplines studying continental evolution, such as seismology, geology, geomorphology, petrology, and geodynamic modeling.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.