Collaborative Research: Shear-wave Splitting and Mantle Dynamics of the North American Plate

合作研究：北美板块的剪切波分裂和地幔动力学

• 批准号: 1719204
• 负责人: Thorsten Becker
• 金额: $ 15.05万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-12-15 至 2019-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1719204&HistoricalAwards=false
• 关键词: Collaborative; Research; Shear; wave; Splitting

Non-technical DescriptionNumerous geological features and phenomena observed on the surface of the Earth -- such as giant mountain belts, deep ocean basins, earthquakes, and volcanoes -- are the results of dynamic processes operating in the Earth's crust, mantle, and core. Therefore, an improved understanding of these processes are essential for the understanding of the origin and development of the Earth and for mitigation of natural hazards. At the present time, however, only the shallowest part of the Earth can be observed directly using cores from drill holes; consequently, an array of computing-intensive geophysical techniques are applied to image the active planet. Those techniques are similar to those used in the hospital to image the human body.Technical DescriptionShear-wave splitting is a fundamental geophysical observation that uniquely indicates the presence of azimuthal anisotropy along the ray path. Such anisotropy is the result of dynamic processes in the Earth's asthenosphere and lithosphere. However, dynamic interpretation of shear-wave splitting requires homogeneous, high quality measurements, and quantitative forward models. This project will measure shear-wave splitting parameters at all of the USArray Transportable Array and other broadband seismic stations in the eastern U.S. and update measurements throughout the North American plate. The data product includes ~10,000 shear-wave splitting measurements that we are merging with ~16,000 measurements that we produced for the western and central U.S. with NSF prior funding via EarthScope. We are utilizing a set of procedures for reliably measuring and ranking the splitting parameters for producing a uniform database, quantifying shear-wave splitting complexity and likely depth of anisotropy along the way. To complement this reference shear-wave splitting database, we are computing a large number of geodynamic forward models of synthetic shear-wave splitting and anisotropic structure for surface wave studies by computing fabrics from mantle flow and simplified tectonic models. This way, we can test which hypotheses for the origin of anisotropy can be reliably discerned, which tectonic scenarios best reflect observations, and how to guide regional refinement of our understanding of continental and upper mantle structure and dynamics. Using this joint approach, we are addressing a number of significant questions regarding the origin of seismic anisotropy, including lithospheric inheritance and recent asthenospheric flow, and the nature of mantle convection underneath the North American plate. In addition, all our measurements, as well as synthetic waveforms, are being openly shared so as to allow others to refine their resulting reference models; this ensures our data product will have a significant impact on a broad range of Earth science questions.

非技术描述在地球表面观察到的非技术地质特征和现象（例如巨型山带，深海盆地，地震和火山）是在地球，地壳，地幔和核心中运行的动态过程的结果。因此，对这些过程的改进理解对于理解地球起源和发展以及减轻自然危害至关重要。然而，目前，只能使用钻孔的岩心直接观察到地球的最浅的部分。因此，应用了一系列计算密集型地球物理技术来对活动行星进行成像。这些技术与医院用于成像人体的技术相似。技术描述 - 波拆分是一种基本的地球物理观察，沿射线路径唯一地表明存在方位角各向异性。这种各向异性是地球天圈和岩石圈中动态过程的结果。但是，对剪切波分裂的动态解释需要均质，高质量的测量和定量远期模型。该项目将在美国东部的所有可运输阵列和其他宽带地震台上测量剪切波分裂参数，并在整个北美板块中进行更新测量。数据产品包括约有10,000张剪切波分裂测量值，我们与我们为美国西部和美国中部生产的约16,000个测量值与NSF先前通过EarthScope进行了资金。 我们正在利用一组程序来可靠地测量和对产生均匀数据库的分裂参数，量化剪切波分裂的复杂性以及沿途各向异性的可能性深度。为了补充此参考剪切波分裂数据库，我们正在计算大量的地球动力学前向模型的合成剪切波分裂和各向异性结构，以通过计算地幔流量和简化的构造模型的织物来进行表面波研究。这样，我们可以可靠地测试哪些对各向异性起源的假设可以可靠地识别，哪些构造场景最好反映观察结果，以及如何指导我们对大陆和上层地幔结构和动态的理解的区域改进。使用这种联合方法，我们解决了有关地震各向异性的起源的许多重大问题，包括岩石圈遗传和最近的软圈流以及北美板块下面的地幔对流的性质。 此外，我们的所有测量以及合成波形都被公开共享，以使其他人完善其所得参考模型。这样可以确保我们的数据产品将对广泛的地球科学问题产生重大影响。