Mapping steps of the crust-mantle boundary over the contiguous United States

美国本土地壳-地幔边界的绘制步骤

• 批准号: 1829496
• 负责人: Zhongwen Zhan
• 金额: $ 10.68万
• 依托单位: California Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-09-01 至 2020-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1829496&HistoricalAwards=false
• 关键词: Mapping; steps; crust; mantle; boundary

The crust-mantle boundary, or the Moho, is an ubiquitous structural discontinuity of the Earth. Lateral variations in Moho geometry, especially Moho offsets, are important to understand the origin and evolution of the crust, and have been the target of many regional and global studies. However, previous methods offer only either spot illumination of the crust or a smoothed Moho topography. Here we propose a scattering-based method to systematically map Moho offsets. Taking advantage of the dense data coverage from the USArray, this work will provide a complete map of Moho offsets over the contiguous United States. The results will shed light on the tectonic evolution of the North American Continent and provide information on the material properties of the lower crust. This project will also support the training of a postdoctoral scholar.The proposed new method relies on surface waves scattered from incident teleseismic body waves. When teleseismic body waves hit a Moho offset, the latter serves as a strong secondary source. As a result, the surface waves are radiated horizontally away from the Moho offset. By back propagating the scattered surface waves with a proper velocity model, the Moho offset can be detected and located. The result of this work can potentially resolve the debate of whether Moho offsets are widespread or not. Regional differences (or not) in the distribution of Moho offsets will provide valuable information on the thick-skinned vs. thin-skinned deformation mechanisms and the effects of lower crust ductile flow in smoothing out Moho offsets. The new method will be applied to USArray data to map Moho topography beneath the United States.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

壳-地幔边界，或称莫霍面，是地球上普遍存在的结构不连续。莫霍面几何形状的横向变化，特别是莫霍面偏移距，对于了解地壳的起源和演化是重要的，并已成为许多区域和全球研究的目标。然而，以前的方法只提供地壳的聚光灯照明或平滑的莫霍面地形。在这里，我们提出了一种基于散射的方法来系统地映射莫霍面偏移。利用美国国家航空航天局的密集数据覆盖范围，这项工作将提供毗邻的美国上空莫霍面偏移量的完整地图。这一结果将揭示北美大陆的构造演化，并提供有关下地壳物质性质的信息。该项目还将支持博士后学者的培训。拟议的新方法依赖于入射的远程地震体波散射的面波。当远震体波到达莫霍面偏移量时，后者就是一个很强的次要震源。结果，面波在水平方向上远离莫霍面偏移量进行辐射。通过采用合适的速度模型对散射表面波进行反向传播，可以检测和定位莫霍面偏移。这项工作的结果可能会解决莫霍偏移量是否广泛存在的争论。莫霍面偏移量分布的区域差异(或非区域差异)将提供关于厚皮和薄皮变形机制以及下地壳韧性流动在平滑莫霍面偏移量方面的有价值的信息。这一新方法将应用于美国阵列数据，以绘制美国境内的莫霍面地形图。这一奖励反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Determining Moho Depth beneath Sedimentary Basins Using Regional Pn Multiples

• DOI: 10.1785/0120180325
• 发表时间: 2019-06
• 期刊: Bulletin of the Seismological Society of America
• 影响因子: 3
• 作者: Chunquan Yu;Z. Zhan;E. Hauksson;E. Cochran;D. Helmberger

Imaging Strong Lateral Heterogeneities Across the Contiguous US Using Body‐To‐Surface Wave Scattering

使用体波散射对美国本土的强烈横向异质性进行成像

• DOI: 10.1029/2020jb020798
• 发表时间: 2021
• 期刊: Journal of Geophysical Research: Solid Earth
• 作者: Yu, Chunquan;Castellanos, Jorge C.;Zhan, Zhongwen
• 通讯作者: Zhan, Zhongwen

The Potential of DAS in Teleseismic Studies: Insights From the Goldstone Experiment

• DOI: 10.1029/2018gl081195
• 发表时间: 2019-02
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Chunquan Yu;Z. Zhan;N. Lindsey;J. Ajo-Franklin;M. Robertson