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: 2218224
• 负责人: Benjamin Holtzman
• 金额: $ 35.47万
• 依托单位: Columbia 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: 2022-09-01 至 2027-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2218224&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.

地幔位于地壳正下方，主要由固体岩石构成；但固体地幔在受到推动或拉动时可以流动，这种流动的速率取决于岩石的特性，例如其温度和温度。组成岩石的微小矿物晶体之间的接触性质可以通过许多不同的现象推动流动，例如：地震后的地震波；大陆冰盖和冰川的融化；地下水的年度补给循环；和提取；这项研究利用对这些现象的观察来测量美国西部、阿拉斯加和冰岛这三个地点下方地幔中的岩石特性和矿物晶体之间的相互作用。最后，新的计算机模型正在综合实验室和现场观察，以了解解释全套数据的基本物理定律。这项研究的结果涉及到预测海平面如何变化等主题。将会因冰盖融化而上升了解木星卫星的潮汐变形是该项目的关键要素，在该项目期间，四名研究生和六名本科生将聚集在一起学习和辩论科学知识。结果和作为本研究的一部分开发的计算机工具。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相关，而端件弹性和稳态行为。尽管人们对瞬态状态的了解相对较好，但这项研究是一项综合研究和推广计划，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中间的潜在观测微物理过程。工作正在利用不同频率的地震和大地测量观测来表征三个地点（美国西部、冰岛和阿拉斯加）的频率依赖性上地幔耗散，但实验工作正在研究位错如何影响。建模工作正在开发新的瞬态蠕变本构定律，并将更复杂的流变学纳入粘弹性变形代码中。固体地球的宽带力学响应；（2）控制粘弹性的微物理过程；以及（3）对大地测量的稳态粘度和地震的热力学状态的推论的影响；更广泛的影响包括培训研究生和本科生、召集 120 名研究人员的综合研讨会，概述瞬态流变学的最新进展，并确定将决定未来十年研究的主题和合作，以及开发交互式 Jupyter 笔记本。在地震衰减和瞬态流变学的背景下引入开源数据科学工具。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力优点和更广泛的影响审查进行评估，被认为值得支持标准。