CSEDI: Coupled Electromagnetic and Geodynamic Study of Thermochemical Piles

CSEDI：热化学桩的电磁与地球动力学耦合研究

• 批准号: 0968923
• 负责人: Chester Weiss
• 金额: $ 29万
• 依托单位: Virginia Polytechnic Institute and State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-06-15 至 2015-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0968923&HistoricalAwards=false
• 关键词: CSEDI; Coupled; Electromagnetic; Geodynamic; Study

One of the great accomplishments in the Earth Sciences in the last few decades has been an increasing appreciation for geologic, thermal, and chemical complexity of Earth's interior, spanning a distance from a few kilometers depth down to the outer boundary of the liquid outer core. This complexity is the result of several interconnected geophysical observations that reveal not only a current snapshot of Earth's state of planetary evolution, but also a 4.6 billion year historical record of global scale geodynamic processes and events that have shaped the surface upon which we live as well as the oceans and atmosphere. Our research focuses on furthering our understanding of Earth's 'deep history' by investigating enigmatic structures known as thermochemical piles, which reside near the base of the mantle, just above the boundary with the core. The lateral extent, size, temperature, composition and geologic significance of these structures is presently a subject of great interest because of their potential relationship to the origin of volcanoes, driving forces for present-day tectonic plates and the fate of long-ago subducted tectonic plates. However, their remoteness from Earth's surface - roughly 3000 kilometers down - makes them an especially elusive target for geophysical investigation. Because of inherent resolution limits and selective sensitivity to the full spectrum of geomaterial properties, no single geophysical method is sufficient for painting a complete picture of this region of the Earth. We propose to study the thermochemical state of the lower mantle through a comprehensive set of numerical experiments, and comparison to observational data, for mutually compatible electromagnetic and geodyamic models. The union of these methods is based on the strong sensitivity of electromagnetic observations to thermochemical variability as manifested in the mantle's electrical conductivity, and the sensitivity of geodynamics modeling to material parameters such as density and viscosity that control the accumulation of material in the lower mantle and that material's thermal structure. Central to these experiments is the over-arching question: How do we, or can we, constrain our knowledge of the thermo-physio-chemical state of the lowermost mantle through geodynamically-compatible electromagnetic observations? Computational experiments will be conducted with a new, parallel electromagnetic MANTle Induction Simulator (project MANTIS) for distributed memory compute architectures, which shares the same underlying mathematical discretization as the CitcomS code that will be used for the geodynamic simulations. This compatibility between discretization methods between the two codes is important for minimizing numerical artifacts as material properties from the electromagnetic domain are mapped into corresponding properties in the geodynamic domain.

在过去的几十年里，地球科学的伟大成就之一是对地球内部地质、热力和化学复杂性的日益认识，从几公里深的地方一直延伸到液态外核的外边界。 这种复杂性是几个相互关联的地球物理观测的结果，这些观测不仅揭示了地球行星演化的当前状态，而且还揭示了46亿年全球尺度地球动力学过程和事件的历史记录，这些过程和事件塑造了我们生活的表面以及海洋和大气。 我们的研究重点是通过调查被称为热化学堆的神秘结构来进一步了解地球的“深层历史”，热化学堆位于地幔底部附近，就在地核边界上方。 这些构造的横向范围、大小、温度、组成和地质意义目前是一个非常令人感兴趣的主题，因为它们与火山的起源、现今构造板块的驱动力和很久以前俯冲构造板块的命运有潜在的关系。 然而，它们远离地球表面-大约3000公里深-使它们成为地球物理调查的一个特别难以捉摸的目标。由于固有的分辨率限制和选择性的敏感性，全谱的geomaterial属性，没有一个单一的地球物理方法是足以描绘一个完整的图片，这一地区的地球。 我们建议研究下地幔的热化学状态，通过一套全面的数值实验，并与观测数据进行比较，相互兼容的电磁和地球动力学模型。 这些方法的结合是基于电磁观测对热化学变化的强烈敏感性，如地幔的电导率，以及地球动力学建模对控制下地幔物质积累和物质热结构的密度和粘度等物质参数的敏感性。 这些实验的核心是一个非常重要的问题：我们如何，或者我们能够，通过地球动力学兼容的电磁观测来限制我们对最低地幔的热物理化学状态的了解？ 计算实验将进行一个新的，并行电磁MANTle感应模拟器（项目MANTIS）的分布式存储器计算架构，共享相同的基本数学离散化的CitcomS代码，将用于地球动力学模拟。 这两个代码之间的离散化方法之间的兼容性是很重要的，最大限度地减少数值伪影的电磁域的材料属性映射到地球动力学域中的相应属性。