Seismic Structure of Central Canada at Multiple Scales

加拿大中部多尺度地震结构

• 批准号: RGPIN-2020-05350
• 负责人: Frederiksen, Andrew
• 金额: $ 2.19万
• 依托单位: University of Manitoba
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=716908
• 关键词: Seismic; Structure; Central; Canada; Multiple

The physical principles of seismology are scale independent, governing waves propagating in a few metres of soil or over distances of thousands of kilometres. However, in practice these different scales are typically examined using different approaches by different people. I propose to address this through a program that exploits scale independence, examining the large-scale structure of North America and adjacent oceans, regional-scale crust and upper-mantle structure in the midcontinent, and small-scale bedrock topography in the Red River valley. The largest-scale project I propose is a new tomographic model of the Canadian lithosphere from two-station surface-wave analysis, combining our recently published two-station data for the Cordillera with eastern-Canada data from the UQM group. The model will be easily updated as new data are available. I also propose a new source of surface-wave data: ocean-bottom seismographs. Using data from past experiments, I will develop dispersion measurement techniques that permit use of ocean-to-shore and ocean-to-ocean paths. This will allow the Canadian model to extend offshore, examining lithosphere beneath the continental shelf and slope. The approach will be more valuable once instruments of the National Facility for Seismic Imaging begin to produce data in the next few years, and will bridge the currently separate domains of continental and marine seismology. I propose to continue work in central North America using data from the Superior Province Rifting Earthscope Experiment. Tomography has not located a major Mid-Continent Rift (MCR) related lithospheric feature, while receiver functions have found a pervasive underplated layer along the MCR axis. The lack of a mantle anomaly beneath the MCR is in contradiction with the large amount of underplated material, unless the underplate was extracted from a deeper source. I will address this gap by applying shear-wave splitting to mantle fabric along the MCR axis, to assess resetting due to rifting. I will constrain the underplate using a transfer-function technique that I developed. Better knowledge of how rifting interacted with lithosphere will aid in understanding North American tectonics and modern rifts. On a small scale, I propose to improve techniques for measuring depth to bedrock using portable seismic equipment, and test their viability in the Red River valley. Existing ambient-noise MASW methods require directional noise; I propose to adapt interferometry used at the crustal scale to recover waves from diffuse noise, which is present everywhere. Better depth-to-bedrock measurement is essential for engineering/geotechnical studies and overburden characterization. The common goal is bridging domains of seismology through scale independence, from continent to ocean and from lithospheric to crustal to near-surface, and so extending the applicability of seismic techniques while better characterizing the tectonic history of North America.

地震学的物理原理与尺度无关，它控制着在几米深的土壤中传播或传播数千公里的波。然而，在实践中，这些不同的尺度通常由不同的人使用不同的方法进行检查。我建议解决这个问题，通过一个程序，利用规模的独立性，研究北美和邻近海洋的大规模结构，区域规模的地壳和上地幔结构在大陆中部，小规模的基岩地形在红河河谷。 我提出的最大规模的项目是一个新的层析成像模型的加拿大岩石圈从两个站的表面波分析，结合我们最近发表的两个站的数据与加拿大东部的数据从UQM组的科迪勒拉。随着新数据的出现，该模型将很容易更新。我还提出了一种新的面波数据来源：海底地震仪。利用过去实验的数据，我将开发分散测量技术，允许使用海洋到海岸和海洋到海洋的路径。这将使加拿大的模型延伸到近海，检查大陆架和陆坡下的岩石圈。一旦国家地震成像设施的仪器在今后几年内开始产生数据，这种方法将更有价值，并将连接目前分离的大陆和海洋地震学领域。 我建议利用上级省裂谷地球镜实验的数据继续在北美洲中部开展工作。层析成像没有找到一个主要的中大陆裂谷（MCR）相关的岩石圈功能，而接收功能发现了一个普遍的底镀层沿着MCR轴。在MCR下缺乏地幔异常与大量的底侵物质相矛盾，除非底侵物质是从更深的来源提取的。我将通过沿MCR轴对地幔组构沿着应用剪切波分裂来解决这个问题，以评估裂谷作用引起的复位。我将使用我开发的传递函数技术来约束底板。更好地了解裂谷如何与岩石圈相互作用将有助于理解北美构造和现代裂谷。 在小范围内，我建议改进使用便携式地震设备测量基岩深度的技术，并在红河河谷测试其可行性。现有的环境噪声MASW方法需要定向噪声，我建议适应在地壳尺度上使用的干涉测量，以恢复波的扩散噪声，这是目前无处不在。更好的基岩深度测量对于工程/岩土研究和覆盖层表征至关重要。 共同的目标是通过尺度独立性，从大陆到海洋，从岩石圈到地壳到近地表，连接地震学领域，从而扩大地震技术的适用性，同时更好地描述北美的构造历史。