EAR-PF: Shear Wave Splitting based on 3D Seismic Wave Simulations: Forward to Inverse Modeling of Upper Mantle and D" Anisotropy

EAR-PF：基于 3D 地震波模拟的剪切波分裂：上地幔和 D" 各向异性的逆向建模

• 批准号: 1855206
• 负责人: Neala Creasy
• 金额: $ 8.7万
• 依托单位: Creasy, Neala Marie
• 依托单位国家: 美国
• 项目类别: Fellowship Award
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1855206&HistoricalAwards=false
• 关键词: EAR; PF; Shear; Wave; Splitting

Dr. Neala Creasy has been granted an NSF EAR postdoctoral fellowship to carry out research and educational plans at Colorado School of Mines (CSM). She will investigate how the Earth's mantle deforms under high pressures and temperatures by making use of the seismic waves produced by earthquakes. Interpreting these seismic waves and how they directly relate to these deformation and mineralogical processes within the mantle is difficult, in part due to necessary assumptions and fundamental limitations inherent to mineral physics experiments at high pressures and temperatures. She will calculate synthetic waveforms for a 3D, realistic Earth to explore how seismic observations relate to mantle deformation. While some prior research has explored the viability of some of the assumptions used to simplify these observations, there are many additional aspects that need to be fully explored to fully understand the complexity of the Earth. Understanding how the Earth deforms via mantle convection is important because this deformation controls the surface expression of plate tectonics, in the form of volcanic activity and earthquakes. This research will help clarify the general understanding of how to use seismic waves to their full potential in understanding current processes in Earth's mantle. Her educational plan involves acting as a research mentor for graduate and undergraduate students at CSM, creating educational material (e.g., infographics, teaching materials) and a Virtual Reality (VR) setup to excite young scientists to pursue basic science, and continued outreach efforts in the local community through organizations including IRIS (Incorporated Research Institutions of Seismology undergraduate internship program) and the Denver Museum of Science. Constraining the pattern and properties of seismic anisotropy in the Earth can help reveal relationships between mineral physics, mantle convection, and seismology. Sources of anisotropy in the lithosphere as frozen-in anisotropy, transition zone, and D" complicate shear wave splitting measurements, resulting in shear wave splitting that can differ from plate motion. If we better understand seismic anisotropy sourced in the lithosphere, we could also better constrain D" anisotropy, which requires correcting for the upper mantle to some extent. Ray theory is commonly used and is appropriate within certain limits, but not all implications have been explored. Ray theory is an infinite frequency approximation and its validity depends on the period of waves, the scale of heterogeneities, the length of its propagation path, and the superposition of multiple arrivals, making interpreting seismic anisotropy observations more difficult. Numerical methods and advances in high-performance computing offer new opportunities to take the full physics of wave propagation into account using realistic 3D Earth structures while conducting seismological observational studies. In this work, Dr. Creasy will explore the assumptions made in shear wave splitting as well as tease out discrepancies between different models and observations of anisotropy within the Earth, by conducting numerical simulations via 3D global wave propagation solver SPECFEM3D_GLOBE. This work will help improve the understanding of how seismic anisotropy observations are related to models of deformation in the Earth's mantle and the sources of anisotropy in the various regions of the crust, upper mantle, and D". These insights will help illuminate discrepancies between different seismic anisotropy observational techniques on regional (e.g. North America and Australia) and global scales. This work will also assist the development of using shear wave splitting in global full waveform inversion addressing appropriate parametrization to describe body-wave anisotropy in the mantle during the inversion process.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.

Neala Creasy博士已获得NSF耳朵博士后研究金，以在科罗拉多州矿业学院（CSM）执行研究和教育计划。她将通过利用地震产生的地震波，调查地球的地幔如何在高压和温度下变形。很难解释这些地震波以及它们如何直接与地幔内的这些变形和矿物学过程直接相关，部分原因是在高压和温度下，矿物质实验固有的必要假设和基本局限性。她将计算3D，逼真的地球的合成波形，以探索地震观测与地幔变形的关系。尽管一些先前的研究探讨了用于简化这些观察结果的某些假设的可行性，但需要充分探索许多其他方面才能充分了解地球的复杂性。了解地球如何通过地幔对流变形很重要，因为这种变形以火山活性和地震的形式控制板构造的表面表达。这项研究将有助于阐明对如何利用地震浪潮的一般理解，以充分了解地球地幔中当前的过程。她的教育计划涉及担任CSM的研究生和本科生的研究导师，创建教育材料（例如，信息图表，教材）和虚拟现实（VR）设置（VR）设置，激发年轻的科学家追求基础科学，并通过包括IRIS的组织在当地社区中继续进行外展工作，包括IRIS（包括IRIS）（包括Seipersology of Seipersology Internssprips Internssips of Seionsology of Seipradsection Intersships of Denterssome Interships of Dentersology of Seipersship of Seioldsssip of Dentersspip）。约束地球上的地震各向异性的模式和特性可以帮助揭示矿物质物理学，地幔对流和地震学之间的关系。岩石圈中各向异性的来源作为冷冻的各向异性，过渡区和D“使剪切波分裂的测量复杂化，从而导致剪切波裂解与板块运动可能不同。如果我们更好地理解地震性各向异性各向异性，我们还可以更好地限制“ d” d'Ayisotrophy，以便在某些范围内进行校正，从而可以校正一些。射线理论通常使用，并且在某些范围内是适当的，但并非所有含义都得到了探索。射线理论是无限的频率近似，其有效性取决于波的周期，异质性的规模，其传播路径的长度以及多个到达的叠加，从而使解释性的地震各向异性观察变得更加困难。高性能计算的数值方法和进步提供了新的机会，可以在进行地震学观察性研究的同时，使用现实的3D地球结构来考虑波浪传播的完整物理。在这项工作中，Creasy博士将通过通过3D全局波传播solver SpecFem3D_Globe进行数值模拟，探索剪切波分裂中所做的假设，并取消不同模型和各向异性观察之间的差异。 This work will help improve the understanding of how seismic anisotropy observations are related to models of deformation in the Earth's mantle and the sources of anisotropy in the various regions of the crust, upper mantle, and D". These insights will help illuminate discrepancies between different seismic anisotropy observational techniques on regional (e.g. North America and Australia) and global scales. This work will also assist the development在全球完整波形反演中使用剪切波拆分，以解决适当的参数化，以描述倒置过程中地幔中的人体各向异性。该奖项反映了NSF的法定任务，并被认为值得通过基金会的知识分子优点和更广泛的影响来通过评估来进行评估。