Collaborative Research: Towards a new framework for interpreting mantle deformation: integrating theory, experiments, and observations spanning seismic to convective timescales

合作研究：建立解释地幔变形的新框架：整合从地震到对流时间尺度的理论、实验和观测

• 批准号: 2311897
• 负责人: Harriet Lau
• 金额: $ 45.18万
• 依托单位: Brown University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-11-01 至 2027-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2311897&HistoricalAwards=false
• 关键词: Collaborative; Research; Towards; new; framework

The Earth’s mantle, which sits directly below the crust, is predominantly made of solid rock; yet the solid mantle can flow when pushed or pulled. The rate of this flow depends on the properties of the rock, such as its temperature, and on the nature of the contacts between the tiny mineral crystals that comprise the rock. The mantle can be pushed to flow by numerous different phenomena, such as: passing seismic waves after an earthquake; melting of continental ice sheets and glaciers; the annual cycle of groundwater recharge and extraction; and the draining of large lakes. This study uses observations of these phenomena to measure the rock properties and the interactions between mineral crystals in the mantle beneath three locations: the western United States, Alaska, and Iceland. Meanwhile, laboratory experiments are probing how samples of rock deform under controlled conditions. Finally, new computer models are synthesizing the lab and field observations to understand the underlying physical laws that explain the full suite of data. The results of this study have a bearing on topics that range from predicting how sea level will rise due to melting ice sheets to understanding tidal deformation on Jupiter’s moons. Outreach and training are key elements of the project. Four graduate students and six undergraduate students are being educated over the duration of the project. Workshops will bring together researchers from diverse scientific disciplines to learn and debate about the scientific outcomes and the computer tools developed as part of this study.There is emerging recognition that the variables describing Earth’s mechanical response to stress, elastic moduli, attenuation, and viscosity, are all frequency dependent. While the end-member elastic and steady-state behaviors are relatively well understood, there remain many fundamental questions regarding the intermediate transient regime. This study is an integrative research and outreach program that combines observational, laboratory, and modeling efforts to measure Earth’s full-spectrum rheological response and illuminate the underlying microphysical processes. Observational work is characterizing frequency dependent upper-mantle dissipation in three locations (western U.S., Iceland, and Alaska) using seismic and geodetic observations of different frequencies but complementary spatial sampling. Experimental work is investigating how dislocations affect transient creep under different temperature and stress conditions and with variable quantities of melt and secondary solid phases. Modeling work is developing new constitutive laws for transient creep and incorporating more sophisticated rheologies in the viscoelastic deformation code. This study is addressing questions about: (1) the broadband mechanical response of the solid Earth; (2) the microphysical processes that control viscoelasticity; and (3) the implications for inferences of steady-state viscosity from geodetic observations and of thermodynamic state from seismic tomography. Broader impacts include training of graduate and undergraduate students, a synthesis workshop that convenes 120 researchers to outline recent advances in understanding transient rheology and to shape the topics and collaborations that will dictate the next decade of inquiry, and development of interactive Jupyter notebooks that introduce open-source data-science tools in the context of seismic attenuation and transient rheology.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.

位于地壳正下方的地幔主要由坚固的岩石组成;然而，坚固的地幔可以在推拉时流动。这种流动的速率取决于岩石的性质，如温度，以及组成岩石的微小矿物晶体之间接触的性质。地幔可以被许多不同的现象推动流动，例如：地震后传递的地震波;大陆冰盖和冰川的融化;地下水补给和提取的年度循环;以及大型湖泊的排水。这项研究利用对这些现象的观察来测量岩石的性质以及三个地点下地幔中矿物晶体之间的相互作用：美国西部，阿拉斯加和冰岛。与此同时，实验室实验正在探索岩石样品在受控条件下如何变形。最后，新的计算机模型正在综合实验室和实地观察，以了解解释全套数据的潜在物理定律。这项研究的结果与预测海平面将如何因冰盖融化而上升到了解木星卫星潮汐变形的主题有关。外联和培训是该项目的关键内容。四名研究生和六名本科生在项目期间接受教育。研讨会将汇集来自不同科学学科的研究人员，学习和讨论作为本研究一部分开发的科学成果和计算机工具。人们逐渐认识到，描述地球对应力、弹性模量、衰减和粘度的机械响应的变量都与频率有关。虽然端元的弹性和稳态行为是比较好的理解，仍然有许多关于中间瞬态制度的基本问题。这项研究是一项综合性的研究和推广计划，结合了观测，实验室和建模工作，以测量地球的全谱流变响应，并阐明潜在的微物理过程。观测工作正在表征三个地点（美国西部，冰岛和阿拉斯加）使用不同频率但互补空间采样的地震和大地测量观测。实验工作是研究在不同的温度和应力条件下，以及在熔体和二次固相数量不同时，位错如何影响瞬态蠕变。建模工作正在开发新的瞬态蠕变本构关系，并在粘弹性变形代码中纳入更复杂的流变学。这项研究涉及的问题有：（1）固体地球的宽带力学响应;（2）控制粘弹性的微物理过程;（3）从大地测量观测中推断稳态粘性和从地震层析成像中推断热力学状态的含义。更广泛的影响包括研究生和本科生的培训，一个综合研讨会，召集120名研究人员概述在理解瞬态流变学方面的最新进展，并塑造将决定未来十年调查的主题和合作，以及开发引入开源数据的交互式笔记本电脑-该奖项反映了NSF的法定使命，并被认为是值得通过使用基金会的智力价值和更广泛的评估来支持的。影响审查标准。