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

俯冲作用在驱动地球板块构造方面起着重要作用，并控制着许多基本的构造过程。俯冲带是许多大地震、火山喷发、海啸和山体滑坡的源头，所有这些都对自然系统和社会产生了重大影响。世界范围内俯冲带的一个耐人寻味的特征是在各种性质和过程中存在沿走向的变化(分段)。了解沿走向的变化是我们理解许多俯冲/弧形过程的关键，例如岩浆作用和地震灾害。太平洋西北部的卡斯卡迪亚俯冲带从扩张中心到弧后，在许多方面都表现出沿走向的变化。通过部署EarthScope可移动阵列、Cascadia倡议两栖阵列和许多灵活的阵列，可以获得极好的数据集。该项目旨在通过为整个卡斯卡迪亚俯冲带生成一个高分辨率的三维速度模型，来约束传入板块的结构与俯冲板块、地幔楔体和岩石圈底部沿走向的变化之间的关系。地壳结构的高分辨率表征也是完善太平洋西北地区地震危险性评估的关键。地震层析成像提供了一种强有力的方法来描绘与俯冲相关的过程的三维，并约束各种分割模式之间的关系。最近的地震研究成像了沿弧前浅层的离散低速体积，在海沟周围的大洋莫霍面下方，以及地幔内的弧后下方，表明了从近海到陆上的结构相关性。我将对环境噪声和区域地震到达进行联合3D全波模拟和反演，这将为Juan de Fuca和Gorda板块在俯冲前后提供尽可能高的分辨率。具体地说，这项提议将解决以下科学问题：(1)胡安德富卡和戈尔达板块在俯冲之前和之后的几何和性质是什么？进入的大洋板块(S)在分割中的作用是什么？(2)从扩张中心到弧后可以成像到什么结构相关性，可以为分割提供洞察？从地壳到上地幔的分段特征的可分辨维度是多少？理解这项研究中获得的与俯冲相关的分段将提供一个关键的视角，可以应用于其他俯冲带，这对地球和行星科学具有广泛的重要性。一名职业生涯早期的女地质学家将为职业发展提供支助，她正在马萨斯大学阿默斯特分校建立一个新的地震学小组。拟议的工作将支持本科生和研究生的培训。相关产品将纳入正在进行的地球科学公众宣传和入门课程。波传播模拟和地面运动地图是教育新英格兰公众了解地震危险的伟大工具。结果将通过Girls Inc.Eureka向8-12年级的女孩介绍！该计划是马萨诸塞州霍利奥克市的Girls Inc.和马萨诸塞州大学之间基于STEM的强大合作。

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.