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

俯冲作用在地球板块构造运动中起着重要作用，并控制着许多基本的构造过程。俯冲带是许多大地震、火山爆发、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重大影响。世界范围内俯冲带的一个有趣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/弧过程的关键，如岩浆活动和地震灾害。西北太平洋卡斯卡迪亚俯冲带从扩张中心到弧后，在许多方面表现出沿走向的变化。随着EarthScope便携式阵列、卡斯卡迪亚倡议两栖阵列和许多灵活阵列的部署，可以获得极好的数据集。该项目旨在通过生成整个卡斯卡迪亚俯冲带的高分辨率三维速度模型，对传入板块的结构与俯冲板片、地幔楔和岩石圈基底的沿走向变化之间的关系提供约束。对地壳结构进行高分辨率定性对于改进太平洋西北部的地震危险性评估也至关重要。地震层析成像提供了一种强有力的方法来描绘俯冲相关过程的三维性，并约束各种分割模式之间的关系。最近的地震研究图像离散低速体积沿着浅深度的前弧，下面的海洋莫霍面周围的海沟，和下面的弧后地幔内，表明从海上到陆上的结构相关性。我将对环境噪声和区域地震波进行联合三维全波模拟和反演，这将为胡安·德富卡和戈尔达板块俯冲前后提供尽可能高的分辨率。具体而言，该提案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形状和性质是什么？进入的大洋板块在板块分割中的作用是什么？(2)从扩张中心到弧后，什么样的结构相关性可以被描绘出来，从而对分割有更深入的了解？从地壳到上地幔的分段特征的可分辨尺度是多少？在这项研究中获得的俯冲相关分割的理解将提供一个关键的角度，可以应用到其他俯冲带，这对地球和行星科学具有广泛的重要性。一名正在UMASS Amherst建立一个新的地震学小组的女性早期职业地球科学家的职业发展将得到支持。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共宣传和入门课程。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害的重要工具。结果将通过女孩公司介绍给8 - 12年级的女孩。尤里卡！计划，一个强大的STEM为基础的合作女孩公司。来自霍利奥克，马萨诸塞州和马萨诸塞大学。

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.