CAREER: Evolutionary Processes in Crustal Seismic Anisotropy

职业：地壳地震各向异性的演化过程

• 批准号: 1252295
• 负责人: Kevin Mahan
• 金额: $ 49.78万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-07-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1252295&HistoricalAwards=false
• 关键词: CAREER; Evolutionary; Processes; Crustal; Seismic

Variation in seismic wave speed as a function of propagation direction, or seismic anisotropy, is an intrinsic property of rocks deformed at high temperature due to preferred mineral alignment and is readily detectable by methods that utilize natural seismic sources (e.g., earthquakes). With a remarkably growing array of techniques, seismic studies are using this phenomenon to detect new structural features in the Earth?s crust and mantle in all types of active and past tectonic settings, including subduction zones, arcs, collisional orogens, active transform faults, and large-scale extensional systems. However, confident interpretations of these features are hampered by the incomplete knowledge of the tectonic processes that govern the development and preservation of seismic anisotropy. This project is utilizing field- and laboratory-based analyses to explore three topical areas that impact the evolution of seismic anisotropy in crustal rocks: 1) prograde and retrograde chemical reactions (metamorphism), 2) the competing roles of different minerals, and 3) the influence of strain type, magnitude, and multiple deformation structures. The goal is to generate predictable relationships between deformation, metamorphism, and seismic anisotropy in crustal rocks that can be further tested by seismic observations and simulations. Such information will lead to increased understanding of seismic images which will allow a better understanding of crustal architecture and interpretation of tectonic processes. Seismic anisotropy is fundamentally a microstructural phenomenon best understood by crossing traditional boundaries between geology and physics. While graduate students will be involved during the academic year, the undergraduate component of the project during summers will focus on the University of Colorado?s Research Experiences in Solid Earth Sciences for Students (RESESS) program, the goal of which is to increase the number of students from underrepresented minority populations entering graduate school in the Earth sciences. The role of this project in the program is designed to positively impact both individual RESESS students and the group as a whole through 1) science mentoring, 2) an annual two-day Front Range multi-disciplinary field trip on Colorado geology, geomorphology, and geophysics for all RESESS interns, and 3) providing a summer fellowship for a graduate student to work with all the interns to provide feedback and to help develop their science presentation skills. The broader goal in this project is to expose graduate and undergraduate students to cross-disciplinary science models and multi-cultural research communities, in as many ways as possible, in order to better prepare these Earth scientists of the future for research challenges in the 21st century.

地震波速随传播方向或地震各向异性的变化是由于优选的矿物排列而在高温下变形的岩石的固有特性，并且很容易被利用自然震源(例如地震)的方法检测到。随着技术的显著发展，地震研究正在利用这一现象在所有类型的活动和过去的构造环境中探测地球-S地壳和地幔的新结构特征，包括俯冲带、弧形、碰撞造山带、活动转换断层和大规模伸展系统。然而，由于对控制地震各向异性发展和保存的构造过程的不完全了解，对这些特征的可信解释受到阻碍。该项目利用现场和实验室的分析，探索影响地壳岩石中地震各向异性演化的三个主要领域：1)前进和倒退化学反应(变质)，2)不同矿物的竞争作用，3)应变类型、大小和多重变形结构的影响。其目标是在地壳岩石的变形、变质和地震各向异性之间产生可预测的关系，可以通过地震观测和模拟进一步测试。这些信息将有助于加深对地震图像的理解，从而更好地了解地壳结构和对构造过程的解释。从根本上讲，地震各向异性是一种微观构造现象，最好的理解方式是跨越地质学和物理学之间的传统界限。虽然研究生将在学年参与，但夏季项目的本科生部分将专注于科罗拉多大学S学生在固体地球科学方面的研究经验(RESESS)项目，该项目的目标是增加来自少数族裔群体的学生进入地球科学研究生院的人数。该项目在该项目中的作用旨在通过1)科学指导，2)为所有RESESS实习生提供为期两天的关于科罗拉多州地质学、地貌学和地球物理学的多学科实地考察，以及3)为研究生提供暑期奖学金，与所有实习生合作，提供反馈并帮助发展他们的科学陈述技能，从而对RESESS学生个人和整个群体产生积极影响。该项目更广泛的目标是让研究生和本科生以尽可能多的方式接触到跨学科的科学模型和多文化研究社区，以便让这些未来的地球科学家更好地为21世纪的研究挑战做好准备。

项目成果

Confronting Solid‐State Shear Bias: Magmatic Fabric Contribution to Crustal Seismic Anisotropy

面对固态剪切偏差：岩浆组构对地壳地震各向异性的贡献

• DOI: 10.1029/2022gl102399
• 发表时间: 2023
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Frothingham, Michael G.;Mahan, Kevin H.;Schulte‐Pelkum, Vera;Goncalves, Philippe;Zucali, Michele
• 通讯作者: Zucali, Michele