CSEDI: Structure and Dynamics of Large-Scale Lower Mantle Compositional Heterogeneity

CSEDI：大规模下地幔成分异质性的结构和动力学

• 批准号: 1161038
• 负责人: Edward Garnero
• 金额: $ 22.03万
• 依托单位: Arizona State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-05-15 至 2015-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1161038&HistoricalAwards=false
• 关键词: CSEDI; Structure; Dynamics; Large; Scale

This two-year proposal focuses on seismological imaging of lower mantle heterogeneity beneath the Pacific Ocean, and numerical convection simulations to put the seismic imaging into a dynamically consistent framework. Our approach is multidisciplinary, and combines seismological analyses by PI Garnero with geodynamical convection simulations by PI McNamara. Recent seismological work has added great detail to deep mantle structure beneath the Pacific, with evidence for large low shear velocity provinces (LLSVPs) that are denser than and chemically distinct from the surrounding mantle. Smaller scale structure includes ultra-low velocity zones (ULVZs) that may preferentially reside at LLSVP margins. Our high resolution seismological experiments aim to better resolve sharp LLSVP edges that appear to extend well up off the core-mantle boundary (CMB), and associated phenomena that depend strongly on LLSVP and mantle properties, including: ULVZ location and structure, CMB topography in vicinity of LLSVP edge, strong heterogeneity within the LLSVP, and relationship to plume upwelling off the LLSVP top. We are focusing on seismic data from southwest Pacific subduction zones recorded in North American, since they densely sample the LLSVP beneath the Pacific Ocean, especially beneath Hawaii. This is a focus area of the proposed work. The seismic findings will inform and be informed by geodynamic simulations that include LLSVP structures. Particular attention will be given to LLSVP morphology and internal structure in the dynamical calculations, as these features will be seismically imaged. Better imaging and modeling LLSVPs will help move us forward in understanding Earth's thermal and mass transport mechanisms, and hence the driving forces in convection that shape the deep structures. Better understanding the nature of convective flow in Earth's deep mantle, how that flow shapes plausible deep and dense compositional reservoirs, and return flow mass transfer that includes plumes is an underlying motivation in this work.This work is important for understanding the structure and dynamics of Earth's deep interior. The nature of convective flow in Earth?s deep mantle, how that flow shapes plausible deep and dense compositional reservoirs, and return flow mass transfer that includes plumes is of interest to the vast spectrum of Earth and planetary scientists. The funding is for a geodynamics graduate student who will be trained on an interdisciplinary research project, and a postdoctoral researcher focused on seismic imaging and geodynamics computations. The PIs are experienced at co-mentoring students and postdocs in a cross-disciplinary fashion.

这项为期两年的提案侧重于太平洋下地幔不均匀性的地震成像，以及将地震成像纳入动态一致框架的数值对流模拟。 我们的方法是多学科的，并结合PI Garnero的地震分析与PI McNamara的地球动力学对流模拟。最近的地震学工作增加了太平洋深部地幔结构的细节，有证据表明大的低剪切速度区（LLSVP）比周围的地幔密度更大，化学成分也不同。 较小规模的结构包括超低速区（ULVZ），可能优先位于LLSVP边缘。我们的高分辨率地震学实验的目的是更好地解决尖锐的LLSVP边缘，似乎延伸到远离核幔边界（CMB），以及强烈依赖于LLSVP和地幔特性的相关现象，包括：ULVZ的位置和结构，在LLSVP边缘附近的CMB地形，LLSVP内的强异质性，以及与LLSVP顶部的羽流上涌的关系。我们关注的是在北美记录的西南太平洋俯冲带的地震数据，因为它们密集地对太平洋下面的LLSVP进行采样，特别是在夏威夷下面。 这是拟议工作的重点领域。 地震调查结果将为包括LLSVP结构在内的地球动力学模拟提供信息。 特别注意将给予LLSVP形态和内部结构的动态计算，因为这些功能将地震成像。更好的成像和建模LLSVP将有助于我们进一步了解地球的热和质量传输机制，从而了解形成深层结构的对流驱动力。 更好地了解地球深部地幔对流的性质，如何塑造合理的深，致密的成分水库，回流质量转移，包括羽流是在这项工作的一个潜在的动机。这项工作是重要的了解地球深部内部的结构和动力学。地球上对流的性质？的深地幔，如何流动形状合理的深和密集的组成水库，并返回流质量转移，包括羽流是感兴趣的广大频谱的地球和行星科学家。这笔资金将用于一名地球动力学研究生，他将接受跨学科研究项目的培训，以及一名专注于地震成像和地球动力学计算的博士后研究员。PI在以跨学科的方式共同指导学生和博士后方面经验丰富。