Collaborative Research: Integration of USArray Magnetotelluric and Seismic Data in the Pacific Northwest

合作研究：太平洋西北地区 USArray 大地电磁和地震数据的整合

• 批准号: 1053628
• 负责人: Gary Egbert
• 金额: $ 34.06万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-15 至 2016-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1053628&HistoricalAwards=false
• 关键词: Collaborative; Research; Integration; USArray; Magnetotelluric

In this project we are combining two geophysical methods for imaging Earth's interior (seismic and electromagnetic) to improve our understanding of the geologic history, and present structure of the Earth in the Pacific Northwest United States. These studies will improve our understanding of the very dynamic Earth in this region, providing information that will ultimately help to mitigate geologic hazards such as earthquakes and volcanic eruptions, and inform efforts to develop natural resources (e.g., geothermal energy). The core dataset for this project is provided by the NSF-funded Earthscope Transportable Array, which provides co-located spatially uniform grids of high quality seismic and electromagnetic (EM) sites. Initial comparison of images obtained from the seismic and EM Earthscope data separately reveal striking similarities, which suggest a common large-scale geometric distribution of different, but plausibly related, material properties. Through this project we are developing more sophisticated methods for integrating the two datasets, with the goal of providing new constraints on physical state and composition of Earth's interior in this region. The methods developed are expected to be more widely applicable, both to similar studies of Earth structure and geologic history in other regions, and for smaller scale applications of joint geophysical imaging to resource exploration or environmental problems.Bulk rock conductivities at crustal and upper mantle depths are strongly influenced by even small amounts of an interconnected conductive phase, making EM methods a powerful tool for mapping fluid distributions and constraining magmatic processes. However, interpretation of EM data in isolation is often ambiguous, as there can be multiple possible causes for high conductivity, and resolution is intrinsically limited by the diffusive nature of EM fields in a conductor. By integrating EM and seismic data non-uniqueness in both can be reduced, providing more powerful and useful constraints on composition and physical state of Earth's interior. With regard to methodology, our approach will span a spectrum, from simple inter-comparison of "unbiased" models obtained by inverting each type of data separately, through testing of hypotheses of common structure, to formal joint inversion. The collaboration is strengthening connections between seismic and EM researchers, and through training of young researchers in complimentary geophysical techniques, promises to enhance future interpretation of Earthscope and other geophysical datasets in the coming years.

在这个项目中，我们结合了两种地球物理方法来成像地球内部(地震和电磁)，以提高我们对美国太平洋西北部地球的地质历史和现今结构的理解。这些研究将增进我们对该地区非常活跃的地球的了解，提供最终将有助于减轻地震和火山喷发等地质灾害的信息，并为开发自然资源(例如地热能)提供信息。该项目的核心数据集由美国国家科学基金会资助的地球望远镜可移动阵列提供，该阵列提供高质量地震和电磁(EM)站点的共址空间统一网格。分别从地震和EM地镜数据获得的图像的初步比较显示出惊人的相似之处，这表明不同但看似相关的材料特性的共同大范围几何分布。通过这个项目，我们正在开发更复杂的方法来整合这两个数据集，目的是对该地区地球内部的物理状态和组成提供新的约束。所开发的方法有望更广泛地适用于其他地区类似的地球结构和地质历史研究，以及联合地球物理成像在资源勘探或环境问题上的较小规模应用。地壳和上地幔深处的块状岩石导电性受到相互关联的导电相的强烈影响，使电磁方法成为绘制流体分布和约束岩浆作用的有力工具。然而，孤立地解释电磁数据往往是模棱两可的，因为高电导率可能有多种可能的原因，而且分辨率本质上受到导体中电磁场的扩散性质的限制。通过整合电磁和地震数据，可以减少两者的非唯一性，为地球内部的组成和物理状态提供更强大和更有用的约束。在方法方面，我们的方法将跨越一个范围，从通过分别倒置每种类型的数据而获得的“无偏”模型的简单内部比较，到对共同结构的假设的检验，再到正式的联合倒置。这项合作正在加强地震研究人员和EM研究人员之间的联系，并通过对年轻研究人员进行免费地球物理技术培训，有望在未来几年加强对地球望远镜和其他地球物理数据的解释。