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的推动作用，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变化（分段）。了解沿走向变化是我们理解许多俯冲/弧过程的关键，例如岩浆活动和地震危险。西北太平洋卡斯卡迪亚俯冲带从扩张中心到弧后，在多个方面表现出沿走向的变化。一个极好的数据集是可用的部署地球范围可移动阵列，卡斯卡迪亚倡议两栖阵列，和许多灵活的阵列。本项目旨在通过建立整个卡斯卡迪亚俯冲带的高分辨率三维速度模型，为进入板块结构与俯冲板块、地幔楔和岩石圈基底沿走向变化之间的关系提供约束条件。地壳结构的高分辨率特征对于改进太平洋西北地区的地震危险性评估也至关重要。地震层析成像为描述与俯冲有关的过程的三维性和约束各种分割模式之间的关系提供了有力的方法。最近的地震研究显示，沿着浅层的前弧、海沟周围的海洋莫霍下以及地幔内的后弧下，存在离散的低速体积，表明了从海上到陆上的结构相关性。我将对环境噪声和区域地震进行联合三维全波模拟和反演，这将为胡安·德富卡和戈达板块在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前后的几何形状和性质是什么？进入的大洋板块在分割中起什么作用？(2)从展布中心到后弧线可以成像哪些构造相关性，从而有助于对分割进行深入了解？从地壳到上地幔的分段特征的可分辨尺寸是多少？本研究获得的与俯冲相关的分段的认识将为其他俯冲带的研究提供一个关键的视角，这对地球和行星科学具有广泛的意义。一位正在马萨诸塞大学阿姆赫斯特分校建立一个新的地震学小组的女性早期职业地球科学家将获得职业发展支持。拟议的工作将支持本科生和研究生的培训。相关产品将整合到正在进行的公众宣传和地球科学入门课程中。波传播模拟和地动图是教育新英格兰公众了解地震危害的好工具。该结果将通过“女孩公司”介绍给8 ~ 12年级的女孩。尤里卡!该项目是马萨诸塞州霍利奥克女孩公司和马萨诸塞大学之间基于stem的强有力合作。

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.