Collaborative Research: An Open Access Experiment to Seismically Image Galapagos Plume-Ridge Interaction

合作研究：加拉帕戈斯羽流-山脊相互作用地震成像的开放获取实验

• 批准号: 1927133
• 负责人: Yang Shen
• 金额: $ 33.52万
• 依托单位: University of Rhode Island
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-03-15 至 2025-02-28
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1927133&HistoricalAwards=false
• 关键词: Collaborative; Research; Open; Access; Experiment

On Earth there are three fundamental ways in which volcanoes form. This study will examine how two of these styles behave in proximity. The Galapagos archipelago is a well-known example of hotspot volcanism, fed by a rising plume of hot mantle, and this system is interacting with the Galapagos Spreading Center (GSC) where volcanism occurs in response to seafloor spreading at the boundary between two tectonic plates moving apart. Scientists have studied the Galapagos hotspot-GSC system for several decades and have long puzzled over persistent discrepancies between geophysical and geochemical observations and physical models for how the pair work together. This study will image how mass and temperature are transported, as well as how magma is generated beneath the Galapagos system, using a technique called seismic tomography. A network of instruments spanning a large area of the islands and adjacent seafloor will be deployed. These seismometers will record seismic waves traveling from distant earthquakes and ambient ground displacement over a period of 15 months. As the seismic waves pass beneath the study area, they respond to differences in mantle composition, temperature, deformation, and the presence of magma. Imaging these properties will allow many unanswered questions particular to the Galapagos system to be addressed. The study will also address the fundamental processes occurring in the shallow part of the mantle that is hot and weak and the interactions with the the cool, stiff overlying part that forms Earth's tectonic plates. This program will train three graduate students in marine geophysics. In addition, an Apply-to-Sail program will allow graduate students and early career scientists from other institutions and community college instructors to participate on the research cruises to gain sea-going training. Lastly, Ecuadorian scientists and graduate students will also participate on the cruises, bolstering science education and international research collaboration.To produce the first mantle seismic view of how mantle plume-ridge interaction really works, an open-access seismic dataset will be collected around the Galapagos system. The experiment and subsequent analyses are designed to address three main scientific questions: (i) At what depths, in what geographic pattern, and by what mechanism does mantle plume material flow northward to the Galapagos Spreading Center and disperse along the ridge? (ii) Do the scale and nature of heterogeneity indicate small-scale, sub-lithospheric convection? and (iii) What is the spatial distribution of melting and volatile release, as well as the associated heterogeneity in composition and rheology due to plume-ridge interaction? The Galapagos system is exceptionally well-suited for such a study given the history of previous investigations of the surface manifestations, the evidence from mantle tomography below the Galapagos Archipelago, and the favorable azimuthal distribution of seismic sources. A large number (53) ocean-bottom, broadband seismometers will be deployed for 15 months in an array spanning the area between the Galapagos Islands and the Western Galapagos Spreading Center. Data from 7 broadband stations on the islands also will be used. The data will undergo initial processing, including ambient noise cross-correlation, and be archived in the IRIS-DMC for immediate public use. Tomography models of isotropic velocity will be produced from body waves, isotropic velocity from the combination of surface waves and ambient noise, as well as radial and azimuthal anisotropy from surface waves. Receiver functions will be analyzed to identify discontinuities related to the lithosphere and melting and shear wave splitting will be used to map anisotropy. Geodynamic models of plume-ridge interaction will be used for hypothesis testing by comparing modeled and observed seismic waveforms, and by using the geodynamic models as a priori information for the tomographic inversions. The project will also substantially advance a broad understanding of mantle plume processes, the asthenosphere, and their interactions with oceanic lithosphere; specifically, the deployment will function as a unit array within the Pacific Array Initiative.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

在地球上有三种基本的火山形成。这项研究将研究这些样式中的两种在接近性方面的行为。加拉帕戈斯群岛（Galapagos Archipelago）是热点火山的一个众所周知的例子，由升起的热地幔泡沫喂养，该系统与加拉帕戈斯散布中心（GSC）相互作用，在那里，火山发生了火山，在响应海底，在两个构造板之间的边界上散布的海底散布。 科学家已经研究了Galapagos Hotspot-GSC系统已有几十年了，并且长期以来一直困扰着地球物理和地球化学观察和物理模型之间的持续差异，以使他们对夫妻如何一起工作。 这项研究将使用称为地震层析成像的技术来想象如何运输质量和温度以及如何在加拉帕戈斯系统下产生岩浆。 将部署跨越岛屿和邻近海底的仪器网络。 这些地震仪将记录在15个月内从遥远的地震和环境地面位移中传播的地震波。 随着地震波越过研究区域，它们对地幔组成，温度，变形和岩浆的存在的差异做出了反应。成像这些属性将允许解决加拉帕戈斯系统的许多未解决问题。这项研究还将解决在地幔的浅层部分中发生的基本过程，该过程既热又弱，并且与形成地球构造板的凉爽，僵硬的上覆的部分相互作用。该计划将培训三名海洋地球物理学的研究生。此外，申请销售计划将允许其他机构和社区大学教师的研究生和早期职业科学家参加研究巡游，以获得海上培训。最后，厄瓜多尔科学家和研究生还将参加巡航，加强科学教育和国际研究合作。为了产生关于披风羽毛池互动如何真正起作用的首个地幔地震观点，将在加拉帕戈斯群岛周围收集开放式地震的地震数据集。实验和随后的分析旨在解决三个主要科学问题：（i）以什么地理模式的深度，地理模式以及地幔羽流材料向北流向加拉帕戈斯散布中心并沿山脊分散的机制？ （ii）异质性的尺度和性质是否表明小规模的下层对流？ （iii）熔融和挥发性释放的空间分布以及由于羽毛状相互作用而引起的组成和流变学的相关异质性是什么？鉴于先前对地表表现的研究的历史，加拉帕戈斯群岛下方的地幔层析成像的证据以及众所周知来源的有利方位分布，加拉帕戈斯系统非常适合此类研究。大量（53）海底，宽带地震仪将在跨越加拉帕戈斯群岛和西加拉帕戈斯酱中心之间的区域中部署15个月。还将使用来自岛上7个宽带站的数据。数据将进行初始处理，包括环境噪声互相关，并在IRIS-DMC中存档，以供立即公开使用。各向同性速度的断层扫描模型将是由人体波，表面波和环境噪声组合的各向同性速度以及径向和方位角各向异性产生的。将分析接收器功能，以确定与岩石圈有关的不连续性，将使用熔融和剪切波分裂来绘制各向异性。通过比较建模和观察到的地震波形，并将地球动力学模型用作层析成像倒置的先验信息，将使用Plume-Ridge相互作用的地球动力模型进行假设检验。该项目还将大大提高人们对地幔过程，软圈及其与海洋岩石圈的相互作用的广泛理解。具体而言，部署将在太平洋阵列计划中充当单位阵列。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子优点和更广泛的影响评估标准通过评估来支持的。