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: 1927087
• 负责人: Garrett Apuzen-Ito
• 金额: $ 32.78万
• 依托单位: University of Hawaii
• 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=1927087&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，火山的形成有三种基本方式。本研究将探讨这两种风格在接近时的表现。加拉帕戈斯群岛是热点火山活动的一个著名例子，由上升的热地幔柱提供燃料，该系统与加拉帕戈斯扩张中心（GSC）相互作用，在那里，火山活动是对两个分开的构造板块之间边界处海底扩张的反应。 科学家们已经研究了加拉帕戈斯热点-GSC系统几十年，并且长期以来一直对地球物理和地球化学观测与物理模型之间的持续差异感到困惑，因为这两者是如何一起工作的。 这项研究将利用一种称为地震层析成像的技术，对质量和温度是如何传输的，以及岩浆是如何在加拉帕戈斯系统下产生的进行成像。 将部署一个覆盖岛屿大面积和邻近海底的仪器网络。 这些地震仪将在15个月的时间内记录来自遥远地震和周围地面位移的地震波。 当地震波通过研究区域下方时，它们会对地幔成分、温度、变形和岩浆存在的差异做出反应。对这些特性进行成像将使加拉帕戈斯星系特有的许多悬而未决的问题得以解决。该研究还将探讨地幔浅层中发生的基本过程，这些过程是热和弱的，以及与形成地球构造板块的凉爽，坚硬的覆盖部分的相互作用。该项目将培养三名海洋生物物理学研究生。此外，一个应用到帆船计划将允许研究生和早期职业科学家从其他机构和社区学院导师参加研究巡航，以获得航海培训。最后，厄瓜多尔的科学家和研究生也将参加这次航行，以加强科学教育和国际研究合作。为了制作第一幅地幔柱-山脊相互作用的地幔地震图，将在加拉帕戈斯系统周围收集一个开放获取的地震数据集。实验和随后的分析旨在解决三个主要的科学问题：（一）地幔柱物质在什么样的深度，以什么样的地理模式，并通过什么机制向北流向加拉帕戈斯扩张中心，并沿沿着脊扩散？(ii)非均匀性的尺度和性质是否表明小尺度的亚岩石圈对流？以及（iii）熔融和挥发物释放的空间分布，以及由于烟羽-洋脊相互作用引起的成分和流变学的相关不均匀性是什么？考虑到以前对地表表现的调查历史、来自加拉帕戈斯群岛下地幔层析成像的证据以及震源有利的方位角分布，加拉帕戈斯系统非常适合进行这样的研究。将在加拉帕戈斯群岛和西加拉帕戈斯扩散中心之间的地区部署大量（53个）海底宽带地震仪，为期15个月。岛上7个宽带站的数据也将被使用。这些数据会经过初步处理，包括进行环境噪音互相关分析，然后存入“综合注册资讯系统-数码港管理系统”，供公众即时使用。将从体波产生各向同性速度的层析成像模型，从表面波和环境噪声的组合产生各向同性速度，以及从表面波产生径向和方位各向异性。接收器功能将被分析，以确定与岩石圈和熔化和剪切波分裂的不连续性将被用来映射各向异性。通过比较模拟和观测到的地震波形，并将地球动力学模型用作层析成像反演的先验信息，将利用羽流-洋脊相互作用的地球动力学模型进行假设检验。该项目还将大大推进对地幔柱过程、软流层及其与海洋岩石圈相互作用的广泛理解;具体而言，该部署将作为太平洋阵列倡议中的一个单元阵列。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。