Crustal and Uppermost Mantle Anisotropy From Seismic Ambient Noise Data Observed on EarthScope/USArray

根据 EarthScope/USArray 观测到的地震环境噪声数据得出的地壳和上地幔各向异性

• 批准号: 0844097
• 负责人: Michael Ritzwoller
• 金额: $ 23.48万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-01-01 至 2011-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0844097&HistoricalAwards=false
• 关键词: Crustal; Uppermost; Mantle; Anisotropy; Seismic

Intellectual Content and MeritThis research aims to develop a new method of seismic tomography called "Eikonal tomography" and apply it to ambient noise and earthquake data recorded on EarthScope/USArray to infer the radial and azimuthal anisotropy structure of the crust and uppermost mantle across the western and central US. The method is based on treating the USArray, including the Transportable Array, the Flexible Array, and the ANSS backbone, explicitly as an array in order to track surface waves that propagate across it. The resulting "phase travel time surfaces" place local constraints on the speed and direction of travel of surface waves, directly revealing azimuthal anisotropy with attendant uncertainties. Eikonal tomography represents a significant improvement in surface wave tomography: it is free from ad-hoc regularization, accurately tracks off-great-circle geometrical waves without iteration, provides accurate error estimates, and presents direct local constraints on azimuthal anisotropy. The method is being applied to ambient noise data observed on the USArray from 2004 through 2010 to estimate isotropic and azimuthally anisotropic phase speeds from 6 sec to 40 sec period. These observations are the basis for the proposed radially and azimuthally anisotropic 3D Vs model of the crust and uppermost mantle. The method is being generalized to Love waves and earthquake data (to provide more information about the mantle). The final results encompass the US from the Pacific in the west through the Great Plains in the east.The goal of the project is to improve understanding of crustal and uppermost mantle anisotropy, which holds a key to knowledge of the deformation history of the crust and mantle. The development of the 3D model of anisotropy would be impossible without the confluence of new methodology (ambient noise tomography, Eikonal tomography) and a unique seismic observational tool (USArray).Broader ImpactsEducational. The data processing and inversion methodology offers a unique educational experience for a graduate student. Intellectual. The ability to resolve crustal from mantle anisotropy provided by the research helps to clarify the interpretation of SKS-splitting. Significant impacts also are anticipated on studies of regional-scale tectonics as well as the deformational state beneath the western and central US and, by extension, similar continental regions elsewhere in the world. Moreover, the methods developed are applicable elsewhere in the world as other regional arrays are installed; e.g., in Europe and China and for PASSCAL experiments. The research team has a strong track record of making data products, models, software, and training available to a wide community. EarthScope: The research is helping to achieve the vision of the USArray -- modeling the Earth beneath the US in unprecedented detail -- and aims to contribute to achieving the US seismological community's vision for EarthScope/USArray.

本研究旨在开发一种称为“Eikonal层析成像”的地震层析成像新方法，并将其应用于EarthScope/USAray记录的环境噪声和地震数据，以推断美国西部和中部地壳和上地幔的径向和方位各向异性结构。该方法是基于处理的USAray，包括可移动阵列，灵活的阵列，和ANSS骨干，明确作为一个阵列，以跟踪表面波的传播across it. The产生的“相位走时表面”的地方限制的速度和传播方向的表面波，直接揭示方位各向异性伴随着不确定性。Eikonal层析成像代表了表面波层析成像的一个显着改进：它是免费的ad-hoc正则化，准确地跟踪非大圆几何波，而无需迭代，提供准确的误差估计，并提出了直接的局部约束方位角各向异性。该方法被应用到环境噪声数据上观察到的USAray从2004年到2010年估计各向同性和方位各向异性相速度从6秒到40秒的周期。这些观测结果是建议的地壳和上地幔的径向和方位各向异性3D Vs模型的基础。该方法正在推广到Love波和地震数据（以提供更多关于地幔的信息）。最终的结果涵盖了美国从西部的太平洋到东部的大平原。该项目的目标是提高对地壳和上地幔各向异性的理解，这是了解地壳和地幔变形历史的关键。如果没有新方法（环境噪声层析成像、Eikonal层析成像）和独特的地震观测工具（USAray）的融合，就不可能开发出各向异性的三维模型。数据处理和反演方法为研究生提供了独特的教育体验。很聪明。该研究提供的解决地壳和地幔各向异性的能力有助于澄清SKS分裂的解释。预计还将对区域尺度构造的研究以及美国西部和中部的变形状态产生重大影响，并由此延伸到世界其他地方的类似大陆地区。此外，随着其他区域阵列的安装，所开发的方法也适用于世界其他地方;例如，在欧洲和中国，以及PASSCAL实验。该研究团队在向广泛的社区提供数据产品、模型、软件和培训方面有着良好的记录。地球镜：这项研究有助于实现USAray的愿景-以前所未有的细节模拟美国下方的地球-并旨在为实现美国地震界对EarthScope/USAray的愿景做出贡献。