Collaborative Research: The Effects of Water and Lithology on the Strength of the North American Lithosphere

合作研究：水和岩性对北美岩石圈强度的影响

• 批准号: 1358664
• 负责人: Derek Schutt
• 金额: $ 10.03万
• 依托单位: Colorado State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-07-01 至 2016-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1358664&HistoricalAwards=false
• 关键词: Collaborative; Research; Effects; Water; Lithology

Nontechnical SummaryA full understanding of mountain-building and earthquake processes requires knowledge of three-dimensional variations in flow strength of continents. Measurements of flow strength are among the major goals of EarthScope, because they are key to understanding the timing and spatial distribution of earthquakes and volcanism, as well as the evolution of North America through time. Characterizing flow strength is challenging, however, because strength is very sensitive to three independent physical properties -- temperature, rock-type, and water content -- whose effects are not easily distinguished using commonly-used geophysical imaging techniques. This project identifies several diverse geophysical measurements that can be combined to separate the effects of temperature, rock type and water in the Earth's crust and upper mantle. In addition, this project is supporting the education of three graduate students and the development of software tools for use in graduate classrooms. Finally, this project is providing maps and other data products that are widely useful to scientists working to understand such diverse topics as likelihood of future earthquakes, volcanic eruptions, and the potential for economic mineral deposits at depth.Technical DescriptionThis project seeks to determine the relative effects of temperature, water and lithology on strength of the North American continental lithosphere. The investigators are estimating temperature variations using uppermost mantle seismic velocities and surface heat flow measurements; characterizing crustal lithology from a combination of gravity and seismic receiver function data; and combining these with measurements of lithospheric flexural rigidity (an integral measure of bending strength) to assess the remainder effects of water on flow rheology. This novel approach to characterizing physical property variations enables in situ estimation of fully three-dimensional flow rheology of the lithosphere, and lends new insight into the dynamical processes of heat and fluid flux that determine mobility versus stability of continental lithosphere. When combined with new constraints on lithospheric mass density variations, these properties promise to revolutionize the Earth Science community's understanding of lithospheric evolution, deformation and dynamical processes. The grant supports research efforts by three graduate students. The Colorado State University PI and two M.S. students are estimating geothermal variations and associated uncertainties, and also developing a series of teaching tools to demonstrate concepts of lithospheric flexure and rheology to undergraduate Earth science students. The Utah State University PI and student are estimating anisotropic flexural rigidity, crustal lithology and thickness, and using the combined measurements to model the water content and rheology of the lithosphere.

要充分了解造山和地震过程，需要了解大陆流动强度的三维变化。流强度的测量是EarthScope的主要目标之一，因为它们是了解地震和火山活动的时间和空间分布以及北美随时间演变的关键。然而，表征流动强度具有挑战性，因为强度对温度、岩石类型和含水量这三种独立的物理性质非常敏感，而使用常用的地球物理成像技术很难区分它们的影响。该项目确定了几种不同的地球物理测量方法，这些测量方法可以结合起来分离温度、岩石类型和地壳和上地幔中水的影响。此外，该项目还支持三名研究生的教育，并开发用于研究生课堂的软件工具。最后，该项目还提供了地图和其他数据产品，这些产品对科学家们了解未来地震、火山爆发的可能性以及深层经济矿藏的潜力等不同主题非常有用。技术描述本项目旨在确定温度、水和岩性对北美大陆岩石圈强度的相对影响。研究人员正在利用最上层地幔地震速度和地表热流测量来估计温度变化；结合重力和地震接收函数资料表征地壳岩性并将这些与岩石圈弯曲刚度（弯曲强度的整体测量）的测量相结合，以评估水对流动流变学的剩余影响。这种描述物理性质变化的新方法能够在现场估计岩石圈的全三维流动流变学，并为确定大陆岩石圈的流动性与稳定性的热和流体通量的动力学过程提供新的见解。当结合岩石圈质量密度变化的新限制时，这些特性有望彻底改变地球科学界对岩石圈演化、变形和动力过程的理解。这笔拨款支持三名研究生的研究工作。科罗拉多州立大学的PI和两名硕士学生正在评估地热变化和相关的不确定性，同时还开发了一系列教学工具，向地球科学本科生演示岩石圈弯曲和流变学的概念。犹他州立大学的PI和学生正在估算各向异性弯曲刚度、地壳岩性和厚度，并使用综合测量来模拟岩石圈的含水量和流变性。