Surface-wave Propagation Across North America: New Methods, Observations and Models

该项目的重点是利用采用各种分析方法在EarthScope/US阵列可移动阵列上记录的数据，调查基模表面波在北美的传播情况。这项研究的一个目标是开发北美地区全面的高分辨率相速度图，以帮助限制该大陆的深层结构。短周期和中周期面波的传播取决于地壳和浅地幔的弹性结构，因此，观测这些波的传播特征有助于约束地球内部这一部分的状态、成分和动力学。可移动地球天文望远镜阵列/USArray正在利用面波为北美地壳和地幔的地震学成像生成一个史无前例的数据集，该项目旨在使用三种方法来利用这些数据。首先，该项目涉及收集美国阵列台站记录的一组新的地震面波偏振观测数据。由于美国阵列站的统一校准，以及用于定位美国阵列站的最先进技术，该数据集非常适合于偏振研究。其次，将最近发展起来的用于确定台间面波频散的两个地震台记录的环境噪声交叉谱的分析方法系统地应用于US阵台站。该方法基于Aki 1957年的开创性论文，允许Love和Rayleigh波的相速度在USArrow的足迹上自动绘制，空间分辨率小于100公里，周期短至5 S。第三，从短周期环境噪声和中期地震信号得出的相速度图被一起用于确定北美大陆地壳和最上地幔的弹性结构。该项目将改进北美面波传播的特征，并将有助于更具体地解释地球内部的组成和热状态。这项研究将产生几个有文件记录的数据集，这些数据集可能对其他希望限制北美以下弹性结构的研究人员有用。

The project is focused on investigating the propagation of fundamental-mode surface waves across North America using data recorded on the EarthScope/USArray Transportable Array employing a variety of methods of analysis. A goal of the research is the development of comprehensive high-resolution maps of phase velocity across North America to help constrain the deep structure of the continent. The propagation of short- and intermediate-period surface waves depends on the elastic structure of the crust and shallow mantle, and observations of propagation characteristics of these waves are therefore useful for constraining the state, composition and dynamics of this portion of the Earth's interior. The Transportable Array of EarthScope/USArray is generating an unprecedented data set for the seismological imaging of the North American crust and mantle using surface waves, and the project aims to exploit these data using three approaches. First, the project involves the collection of a new set of observations of surface-wave polarization for earthquakes recorded on USArray stations. Owing to the uniform calibration of USAarray station, and the state-of-the-art technology used to orient USArray stations, this data set is ideally suited for polarization studies. Second, a recently developed method of analyzing cross spectra of ambient noise recorded on two seismic stations for the determination of inter-station surface-wave dispersion is applied systematically to USArray stations. The method, which is based on Aki's seminal 1957 paper, allows Love and Rayleigh wave phase velocities to be mapped automatically across the footprint of USArray at a spatial resolution smaller than 100 km, and at periods as short as 5 s. Third, the phase velocity maps derived from short-period ambient noise and intermediate-period earthquake signals are used, together, to determine the elastic structure of the crust and uppermost mantle of the North American Continent.The project will lead to an improved characterization of surface-wave propagation across North America and will facilitate more specific interpretation of the composition and thermal state of the Earth's interior. Several documented data sets that can be useful for other investigators wishing to constrain the elastic structure beneath North America will result from the research.