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.

地球的地幔位于地壳下方，主要由坚固的岩石制成。然而，固体地幔在推或拉动时可以流动。该流量的速率取决于岩石的特性，例如其温度，以及构成岩石的微小矿物晶体之间的接触性质。地幔可以通过许多不同的现象来推动地震，例如：地震后传递地震波；连续的冰盖和冰川融化；地下水补给和提取的年度周期；和大湖泊的排水。这项研究使用对这些现象的观察来测量岩石特性以及三个位置下地幔中的矿物晶体之间的相互作用：美国西部，阿拉斯加和冰岛。平均指的是，实验室实验正在探测在受控条件下岩石的样本变形。最后，新的计算机模型正在综合实验室和现场观测值，以了解解释完整数据套件的基本物理定律。这项研究的结果与主题有关，范围从预测由于融化冰盖而导致海平面的上升，以了解木星卫星上的潮汐变形。推广和培训是该项目的关键要素。在该项目期间，正在对四名研究生和六名本科生进行教育。研讨会将使来自潜水员科学学科的研究人员聚集在一起，以学习并破坏作为本研究的一部分开发的科学成果和计算机工具。新兴的认识是，变量描述了地球对压力，弹性模量，衰减和粘度的机械响应均取决于频率。尽管最终成员的弹性和稳态行为相对充分理解，但有关中间瞬态制度的基本问题仍有许多基本问题。这项研究是一项综合研究和外展计划，结合了观察性，实验室和建模工作，以测量地球的全谱性流变学反应并阐明潜在的微物理过程。观察性工作是在三个位置（美国西部，冰岛和阿拉斯加）使用不同频率的地震和大地测量观测来表征频率依赖的上壳耗散，但完全空间采样。实验工作正在研究错位如何在不同的温度和应力条件下影响瞬态蠕变，并且熔融数量变化和二级固相。建模工作正在开发新的本构法律，用于粘弹性变形代码中的瞬态蠕变和日益复杂的流变。这项研究正在解决以下问题：（1）固体土的宽带机械响应； （2）控制粘弹性的微物理过程； （3）对从地震层析造影的测量观测和热力学状态的稳态粘度推断的意义。 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法定使命，并使用基金会的知识分子优点和更广泛的影响标准通过评估被认为是宝贵的支持。