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

地球大陆岩石圈相对稳定的核心，被称为克拉通，被认为是“稳定的”构造特征，通常对破坏和再循环具有弹性。这种韧性并不意味着克拉通不会因构造作用而变形。在全球范围内，在克拉通内部，有大量的局部下沉、隆起和解体，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发源地。尽管克拉通及其相关的构造特征具有重要的科学和社会意义，但目前尚不清楚这些特征是如何形成的，以及克拉通如何在漫长的(数十亿年)构造演化历史中幸存下来。该项目将通过构建多种类型的地震模型来研究北美中大陆内部的地震特征。这些地震模型将为改变北美克拉通岩石圈的构造机制提供约束。该项目将支持研究生和本科生进行地震数据分析和解释。通过与普渡大学外展办公室的合作，该项目将制作一系列关于美国中西部地质和构造的教育视频，向公众开放。克拉通通常被认为是“稳定的”构造特征，通常对破坏和回收具有弹性。随着最近从地球物理成像、地质调查和地球动力学模拟中观察到的支持克拉通岩石圈重大结构和成分修改的观察，这一想法越来越受到质疑。该项目将利用多种方法建立北美克拉通内部的多种地震模型，包括全波环境噪声层析成像、平面波偏移接收函数和地震各向异性分析。有了新的结构限制，该项目将系统地评估先前提出的关于克拉通岩石圈演化的四种终端成员设想。这个项目的结果将阐明地球科学中的几个基本问题：1)是什么过程改变了稳定的克拉通？2)克拉通为什么以及如何在漫长的构造事件历史中幸存下来？3)既有构造对后期变形有何影响？该项目的成果也对研究大陆演化的地学学科具有重要影响，如地震学、地质学、地貌学、岩石学和地球动力学模型。该奖项反映了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。

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.