Analysis of Seismic Data from the USArray Project to Determine Crust and Uppermost Mantle Structure Beneath the United States

分析 USArray 项目的地震数据以确定美国下方的地壳和上地幔结构

• 批准号: 1358510
• 负责人: Peter Shearer
• 金额: $ 17.99万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-07-01 至 2016-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1358510&HistoricalAwards=false
• 关键词: Analysis; Seismic; Data; USArray; Project

During the last ten years, NSF's USArray Project has deployed thousands of seismometers across the United States to record both local and distant earthquakes. Analyses of these data have provided greatly improved images of the structure of Earth's crust and mantle beneath the United States. This project studies earthquakes and quarry blasts recorded by USArray at distances up to 1600 km away (1000 miles), which are particularly useful for probing crustal thickness and the structure of the uppermost mantle, i.e., immediately below the crust at depths of about 35 to 50 kilometers (about 20 to 30 miles). Maps showing variations in the measured velocities of seismic waves in this region provide clues regarding the history and evolution of mountains, faults, and other geological features, including the Colorado Plateau and Yellowstone volcanism. This project builds on previously NSF funded work in the western United States to focus on more recent USArray data from the eastern United States.In particular, the project uses regional seismic phases such as Pn, Sn, Pg and Lg, to produce new maps of crustal thickness and both isotropic and anisotropic variations in uppermost mantle P and S velocity that can be related to many surface tectonic features. These results generally agree with previous studies in their large-scale patterns but show more detail in many regions. Owing to its relatively sparse station coverage and lack of earthquakes, the eastern United States has been much less studied than the west, so the most recent USArray station deployments provide a valuable opportunity to probe its crust and uppermost mantle structure. This project will provide new crustal thickness maps, estimates of crustal Vp/Vs ratios, maps of uppermost mantle variations in seismic velocity and azimuthal anisotropy. In addition, analyses of Sn propagation efficiency and Pg and Lg times and amplitudes are planned to resolve lower crustal velocities and attenuation. These results will complement shear-wave splitting and surface- and body-wave tomography studies by providing superior resolution for structures at lower crustal and uppermost mantle depths.

在过去十年中，美国国家科学基金会的 USArray 项目已在美国各地部署了数千台地震仪来记录当地和遥远的地震。 对这些数据的分析极大地改善了美国地下地壳和地幔结构的图像。 该项目研究 USArray 记录的距离最远 1600 公里（1000 英里）的地震和采石场爆炸，这对于探测地壳厚度和最上地幔的结构特别有用，即紧邻地壳下方约 35 至50 公里（约 20 至 30 英里）。 显示该地区地震波测量速度变化的地图提供了有关山脉、断层和其他地质特征（包括科罗拉多高原和黄石火山活动）的历史和演化的线索。 该项目以之前 NSF 资助的美国西部工作为基础，重点关注美国东部最新的 USArray 数据。特别是，该项目使用 Pn、Sn、Pg 和 Lg 等区域地震相位来生成新的地图地壳厚度以及上地幔 P 和 S 速度的各向同性和各向异性变化可能与许多表面构造特征有关。这些结果在大范围模式上与之前的研究基本一致，但在许多地区显示了更多细节。由于台站覆盖范围相对稀疏且缺乏地震，美国东部的研究比西部少得多，因此最近的 USArray 台站部署为探测其地壳和上地幔结构提供了宝贵的机会。该项目将提供新的地壳厚度图、地壳 Vp/Vs 比值估计、地震速度和方位各向异性的最上地幔变化图。此外，计划对 Sn 传播效率以及 Pg 和 Lg 时间和振幅进行分析，以解决较低地壳速度和衰减问题。 这些结果将为下地壳和上地幔深度的结构提供卓越的分辨率，从而补充剪切波分裂以及表面波和体波断层扫描研究。