Constructing a model from the spreading centers to backarc: Resolving geophysical characteristics of segmentation in Cascadia

构建从扩张中心到弧后的模型：解析卡斯卡迪亚分段的地球物理特征

• 批准号: 1624077
• 负责人: Haiying Gao
• 金额: $ 28.85万
• 依托单位: University of Massachusetts Amherst
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-01 至 2020-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1624077&HistoricalAwards=false
• 关键词: Constructing; model; spreading; centers; backarc

Subduction plays a major role in driving plate tectonics on Earth and controls many fundamental tectonic processes. Subduction zones are the source of many great earthquakes, volcanic eruptions, tsunamis, and landslides, all of which have significant impacts on natural systems and society. One intriguing characteristic of subduction zones worldwide is the presence of along-strike variation (segmentation) in a wide variety of properties and processes. Understanding along-strike variation is key to our understanding of many subduction/arc processes, such as magmatism and earthquake hazards. The Cascadia subduction zone in the Pacific Northwest exhibits along-strike variation in many aspects, spanning from the spreading center to the backarc. A superb data set is available with the deployments of the EarthScope Transportable Array, the Cascadia Initiative Amphibious Array, and many flexible arrays. This project aims to provide constraints on the relationships between structure of the incoming plate and the along-strike variation of the subducted slab, mantle wedge, and lithospheric base by generating a high-resolution three-dimensional velocity model for the entire Cascadia subduction zone. High-resolution characterization of the crust structure is also critical to refine seismic hazard assessment in the Pacific Northwest. Seismic tomography provides a powerful way to delineate the three dimensionality of subduction-related processe and to constrain the relations among the various modes of segmentation. Recent seismic studies image discrete low-velocity volumes along the forearc at shallow depths, beneath the oceanic Moho around the trench, and beneath the back-arc within the mantle, indicating structural correlations from offshore to onshore. I will implement a joint 3D full-wave simulation and inversion of ambient noise and regional earthquake arrivals, which will provide the highest possible resolution for the Juan de Fuca and Gorda plates prior to and after subduction. Specifically, this proposal will address the following scientific questions: (1) What are the geometry and properties of the Juan de Fuca and Gorda plates prior to and after subduction? What is the role of the incoming oceanic plate(s) on the segmentation? (2) What structural correlations can be imaged from the spreading centers to the backarc that may give insight to the segmentation? What are the resolvable dimensions of the segmented features from the crust to the upper mantle? Understanding of subduction-related segmentation obtained in this study will provide a key perspective that can be applied to other subduction zones, which has broad importance to Earth and Planetary Sciences. One female early-career geoscientist, who is in the process of establishing a new seismology group at UMASS-Amherst, will be supported for the career development. The proposed work will support training of undergraduate and graduate students. The related products will be integrated into ongoing public outreach and introductory classes in Earth Science. Wave propagation simulation and ground motion maps are great tools to educate the public in New England about seismic hazards. The outcome will be introduced to 8th-12th grade girls through the Girls Inc. Eureka! Program, a strong STEM-based collaboration between Girls Inc. of Holyoke, Massachusetts and UMASS.

俯冲在地球上驱动板构造方面起着重要作用，并控制许多基本的构造过程。俯冲区是许多巨大地震，火山喷发，海啸和滑坡的来源，所有这些都会对自然系统和社会产生重大影响。全球俯冲区的一个有趣的特征是在各种特性和过程中存在沿形变化（分割）。了解沿局势的变化是我们理解许多俯冲/弧形过程的关键，例如岩浆和地震危害。太平洋西北地区的卡斯卡迪亚俯冲带在许多方面都沿着史上的变化，从扩张中心到后弧。可以通过可运输阵列的部署，Cascadia倡议两栖阵列和许多灵活的阵列提供出色的数据集。该项目旨在通过为整个Cascadia俯冲区的高分辨率三维速度模型产生高分辨率的三维速度模型，从而对传入板的结构与俯冲板，地幔楔和岩石圈基础之间的关系之间的关系提供约束。地壳结构的高分辨率表征对于在太平洋西北地区的完善地震危害评估也至关重要。地震断层扫描提供了一种有力的方法来描述俯冲相关过程的三个维度，并限制各种分割模式之间的关系。最近的地震研究图像沿浅深度的前臂，在沟槽周围的海洋莫霍（Oceanic Moho）下方，在地幔内的背面弧下方的海洋莫霍（Oceanic Moho）下图像离散的低速度体积，表明从近海到陆上的结构相关性。我将实施一个联合3D全波模拟和环境噪声和区域地震到达的倒置，该噪声将在俯冲前后为Juan de Fuca和Gorda板提供最高的分辨率。具体而言，该提案将解决以下科学问题：（1）在俯冲之前和之后，Juan de Fuca和Gorda板的几何和特性是什么？传入的海洋板在分割中的作用是什么？ （2）可以从扩展中心到可能深入了解分割的后脑的哪些结构相关性？从地壳到上地幔的分段特征的可分离尺寸是什么？了解本研究中获得的俯冲相关分段将提供一个关键的观点，可以应用于其他俯冲带，该区域对地球和行星科学具有广泛重要性。一个正在UMass-Amherst建立新的地震学小组的女性早期地球科学家将得到职业发展的支持。拟议的工作将支持对本科生和研究生的培训。相关产品将纳入地球科学的持续公开外展和入门班。波浪传播模拟和地面运动图是向新英格兰公众教育地震危害的绝佳工具。结果将通过女子公司尤里卡（Eureka）介绍给8至12年级的女孩！计划是马萨诸塞州霍利奥克和UMass的Girls Inc.之间的基于STEM的强大合作。