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.

地震波速度的变化作为传播方向的函数，或地震各向异性，是岩石在高温下变形的固有特性，这是由于首选的矿物排列，并且很容易通过利用自然震源（例如地震）的方法检测到。随着技术的显著增长，地震研究正在利用这种现象来探测地球上新的结构特征。包括俯冲带、弧形、碰撞造山带、活动转换断裂和大规模伸展体系在内的各种类型的活动和过去构造背景下的地壳和地幔。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，对这些特征的自信解释受到了阻碍。本项目利用现场和实验室分析来探索影响地壳岩石地震各向异性演化的三个主题：1)顺行和逆行化学反应（变质作用），2)不同矿物的竞争作用，以及3)应变类型、震级和多种变形结构的影响。目标是在地壳岩石中产生可预测的变形、变质作用和地震各向异性之间的关系，这些关系可以通过地震观测和模拟进一步验证。这些信息将增加对地震图像的理解，从而更好地理解地壳结构和解释构造过程。地震各向异性基本上是一种微观结构现象，最好通过跨越地质学和物理学之间的传统界限来理解。虽然研究生将在学年期间参与，但夏季项目的本科生部分将集中在科罗拉多大学？该计划的目标是增加来自代表性不足的少数民族的学生进入地球科学研究生院的人数。该项目旨在通过以下方式对RESESS学生个人和整个团队产生积极影响：1)科学指导；2)每年为RESESS实习生提供为期两天的科罗拉多地质学、地貌学和地球物理学多学科实地考察；3)为研究生提供暑期奖学金，与所有实习生一起提供反馈，帮助他们发展科学演讲技能。该项目的更大目标是让研究生和本科生尽可能多地接触跨学科的科学模型和多元文化的研究社区，以便更好地为这些未来的地球科学家做好准备，迎接21世纪的研究挑战。

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