The Seismic Structure, Thermal State, and Anisotropy of the Crust and Uppermost Mantle Beneath the Contiguous US

美国本土下方地壳和上地幔的地震结构、热状态和各向异性

• 批准号: 1252085
• 负责人: Michael Ritzwoller
• 金额: $ 26.36万
• 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: 2013-04-01 至 2016-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1252085&HistoricalAwards=false
• 关键词: Seismic; Structure; Thermal; State; Anisotropy

Previous investments in surface wave data processing and inversion methodologies together with the growth of the USArray Transportable Array (TA) provide the unprecedented opportunity to obtain an observationally constrained, uniformly processed view of the crust and uppermost mantle across the entire US. By the end of the grant period, the TA will extend across the entire US and the proposed research will produce a synoptic view of the seismic and thermal structure of the North American continent. The primary focus is to construct 3D models of radial and azimuthal anisotropy in the crust and uppermost mantle across the contiguous United States using surface waves extracted from ambient noise and earthquake data as well as receiver functions. Thermal modeling of isotropic velocities via thermodynamically constrained inversions will allow estimates of uppermost mantle temperature, mantle heat flux, and the thickness of the thermal lithosphere across the continent. All inversions leverage recent advances in surface wave tomography methods (e.g., eikonal and Helmholtz tomography) to improve the fidelity of estimated wave speeds. A key component of this work is the estimation of uncertainties using Monte Carlo and related Bayesian statistics from primary measurements to the final seismological models.The proposed research possesses a substantial technical component, involving the application of recently developed methods of seismic data processing and tomography to USArray TA data observed between 2011 and 2015. The scientific motivations, however, are (1) to improve understanding of crustal and uppermost mantle anisotropy, which holds the key to knowledge of the deformation undergone by the continent and the vertical distribution of mechanical coupling in the crust and uppermost mantle, and (2) to illuminate the thermal state of the uppermost mantle. Ambient noise provides unique sensitivity to crustal structure and the ability to separate crustal from mantle anisotropy. The introduction of receiver function data further improves the vertical resolution of the model. Thermodynamically constrained inversions promise new information on the thermal state of the uppermost mantle across the entire contiguous US.The seismological models and the data used to construct them will be archived and shared with the broader geoscience community. A collaboration with the IRIS-DMS has allowed the DMC to archive and distribute ambient noise cross-correlations and continued development of similar products is envisioned. Higher level data products such as dispersion maps, 3-D models, receiver functions, and research codes are delivered to the general public through dynamically updated, internet-accessible databases at CU-Boulder: http://ciei.colorado.edu/ritzwoller_m. The proposal will support two PhD graduate students. Finally, the PI is collaborating with the USGS to use the 3-D models from CU-Boulder to improve location capabilities for small earthquakes across the US. The proposed research will allow these improvements to extend into the central and eastern US where the proposed research will construct a high resolution 3-D model of the crust and uppermost mantle, providing a lasting element to the legacy of the USArray TA.

先前在面波数据处理和反演方法方面的投资以及USAray可移动阵列（TA）的增长为获得整个美国地壳和上地幔的观测约束、统一处理视图提供了前所未有的机会。到资助期结束时，TA将扩展到整个美国，拟议的研究将产生北美大陆地震和热结构的概要视图。主要的重点是构建3D模型的径向和方位各向异性的地壳和上地幔横跨美国本土使用从环境噪声和地震数据以及接收器功能提取的表面波。热模拟各向同性的速度，通过热约束反演将允许估计最上层地幔温度，地幔热通量，整个大陆的热岩石圈的厚度。所有反演都利用了表面波层析成像方法的最新进展（例如，程函和亥姆霍兹层析成像）以提高估计的波速的保真度。这项工作的一个关键组成部分是估计的不确定性，使用蒙特卡罗和相关的贝叶斯统计从初步测量到最终的地震model.The拟议的研究具有实质性的技术组成部分，涉及应用最新开发的地震数据处理和层析成像的方法USAray TA数据之间观察到2011年和2015年。其科学动机是（1）提高对地壳和上地幔各向异性的认识，这是认识大陆变形和地壳和上地幔力学耦合垂直分布的关键;（2）阐明上地幔的热状态。环境噪声提供了对地壳结构的独特敏感性和区分地壳与地幔各向异性的能力。接收函数数据的引入进一步提高了模型的垂直分辨率。热动力学约束反演承诺在整个美国毗连的最上层地幔的热状态的新信息。地震模型和用于构建它们的数据将被存档，并与更广泛的地球科学界共享。与IRIS-DMS的合作使DMC能够存档和分发环境噪声互相关，并设想继续开发类似的产品。更高级别的数据产品，例如色散图、3D模型、接收器功能和研究代码，通过CU-Boulder的动态更新、可通过互联网访问的数据库提供给公众：http://ciei.colorado.edu/ritzwoller_m。该提案将支持两名博士研究生。最后，PI正在与USGS合作，使用CU-Boulder的3D模型来提高美国各地小地震的定位能力。拟议的研究将使这些改进扩展到美国中部和东部，在那里拟议的研究将构建地壳和最上层地幔的高分辨率三维模型，为USAray TA的遗产提供持久的元素。