Structure and dynamics of the subcontinental lithospheric mantle over the Central and Eastern North American continent, constrained by numerical modeling based on tomography models

基于层析成像模型的数值模拟约束北美大陆中部和东部次大陆岩石圈地幔的结构和动力学

• 批准号: 2240943
• 负责人: Claudia Adam
• 金额: $ 17.72万
• 依托单位: Kansas State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-05-01 至 2026-04-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2240943&HistoricalAwards=false
• 关键词: Structure; dynamics; subcontinental; lithospheric; mantle

Most earthquakes happen near or along the edges of tectonic plates, and forces causing them are reasonably well understood. Earthquakes in the Central and Eastern United States (CEUS), far from any plate boundary, are a bit of a mystery; scientists cannot agree on why they happen. Dr. Adam and her team will investigate how convective motions in the Earth's mantle, hundreds of miles below the surface, may contribute to forces in the brittle crust, causing at least some CEUS earthquakes. Her study makes use of data from the USArray, an NSF-funded national experiment in which a dense network of seismometers was left out to record earthquakes for years at a time. In addition to a thorough 'catalogue' of CEUS earthquakes (size, timing and location), the US Array has provided new information on the structure of the subsurface. Dr. Adam will use this information to build detailed computational models and perform calculations of mantle convection and forces in the crust (and earthquakes) this convection might cause. She will also train a graduate student and participate in Kansas State University's science education and outreach programs for girls, young people from groups that are underrepresented in the sciences, and the broader public. Data collected through the US Array and other complementary networks have provided a much clearer and more accurate image of surface deformation and seismic velocity structure of the crust and mantle in the United States. Dr. Adam will use these data, together with ConvRS geodynamic models, to assess the role of mantle dynamics on stresses and intraplate seismicity in the Central and Eastern United States. A preliminary step will be to sort through several published tomographic models using a systematic method to remove spurious features. She and her team will interpret tomographic velocity data with thermodynamic and anelasticity theory to infer mantle and crust rheology and buoyancy forces, making geodynamic model inputs as compatible as possible with geophysical observations. The effects of the Glacial Isostatic Adjustment (GIA), based on previous studies, will also be represented. Model outputs (stress axis orientation and geoid height) will be compared to observations, and sensitivity of these results to parameter variations will be assessed. The main questions Dr. Adam plans to address are (1) What are the structure and dynamics of the sub-continental lithospheric mantle? (2) How do they correlate with intraplate seismicity? and (3) Which part of the observed seismicity is related to shallow crustal and lithospheric structures, which is due to GIA, and which is due to deeper processes?This project is jointly funded by the NSF Geophysics Program and the Established Program to Stimulate Competitive Research (EPSCoR).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.

大多数地震发生在构造板块附近或沿其边缘，并且引起地震的作用力已被很好地理解。美国中部和东部 (CEUS) 远离板块边界的地震有点神秘。科学家们无法就它们发生的原因达成一致。亚当博士和她的团队将研究地表以下数百英里的地幔中的对流运动如何对脆性地壳产生作用力，从而至少引起一些 CEUS 地震。她的研究利用了 USArray 的数据，USArray 是一项由美国国家科学基金会 (NSF) 资助的国家实验，其中密集的地震仪网络被忽略，用于一次记录地震数年。除了完整的 CEUS 地震“目录”（规模、时间和位置）之外，US 阵列还提供了有关地下结构的新信息。 Adam 博士将利用这些信息建立详细的计算模型，并计算地幔对流以及该对流可能引起的地壳力（以及地震）。她还将培训一名研究生，并参加堪萨斯州立大学针对女孩、科学领域代表性不足群体的年轻人以及更广泛公众的科学教育和外展计划。通过美国阵列和其他补充网络收集的数据为美国地壳和地幔的表面变形和地震速度结构提供了更清晰、更准确的图像。 Adam 博士将使用这些数据以及 ConvRS 地球动力学模型来评估地幔动力学对美国中部和东部应力和板内地震活动的作用。第一步将是使用系统方法对几个已发布的断层扫描模型进行排序，以消除虚假特征。她和她的团队将利用热力学和滞弹性理论解释断层扫描速度数据，以推断地幔和地壳流变学和浮力，使地球动力学模型输入尽可能与地球物理观测相兼容。基于之前的研究，冰川均衡调整（GIA）的影响也将得到体现。模型输出（应力轴方向和大地水准面高度）将与观测结果进行比较，并评估这些结果对参数变化的敏感性。 Adam博士计划解决的主要问题是（1）次大陆岩石圈地幔的结构和动力学是什么？ (2)它们如何与板内地震活动相关？ (3) 观测到的地震活动的哪一部分与浅层地壳和岩石圈结构相关，哪一部分是 GIA 造成的，哪一部分是更深层次的过程造成的？该项目由 NSF 地球物理计划和刺激竞争既定计划联合资助研究 (EPSCoR)。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。