CAREER: New imaging of mid-ocean ridge systems at the Galápagos triple junction

加拉帕戈斯三重结合部大洋中脊系统的地震成像板块构造的一个关键要素是一个约50,000公里长的环绕地球的火山山脉，在那里板块不断分离，岩浆从地球内部上升到冷却。这一点已经被理解了70多年，但关于这些系统的深层结构的细节仍然没有解决。问题是，这些山脉中的大多数位于海洋中央数英里深的水下(“海洋中脊”；MORS)。地震学测量是观测地球数十公里的主要工具。该项目涉及一项多年的海底地震仪(OBS)布置，横跨和沿着其中两个MORS，在其中三个海脊相交的“三个交界处”位置。这些仪器记录的地震信号将被用来建立MORS深处固体地球的三维模型。该项目包括外联和培训活动。该项目将有高中生参与，并将通过在探险期间制作电影来教育公众。它将通过科学考察和课堂作业为本科生和研究生提供研究和教育机会。该计划将包括早期职业调查人员，并为规划海上科学考察生成一本开源手册。这些数据将增强对地质灾害的理解和对整个地球的成像。大约5万公里长的全球大洋中脊(MOR)系统，65%的构造板块就是在这里产生的，可以说是我们星球表面的决定性特征。然而，海洋伸展的基本方面仍然知之甚少，包括驱动大洋中脊上升流的机制，以及成熟大洋板块组构和间断的起源。该项目涉及跨越加拉帕戈斯三重结点的多年宽带海底地震仪部署，涉及两个历时重叠的约40个台站阵列，沿Strike跨越400公里，垂直于太平洋-科科斯和科科斯-纳斯卡扩散中心。对这些MORS的面波和体波层析成像，包括对地震衰减、散射相和地震各向异性的测量，将提供前所未有的岩石圈和软流层结构的空间和方法覆盖。这项工作将：1)检验动力上升流的预测特征；2)拍摄可能持续在成熟岩石圈中的MOR熔融、脱水和剪切结构的图像；3)探索山脊下地幔流动的三维组织；4)利用下伏地幔的扩张速率和山脊迁移的对比来衡量这些参数对山脊动力学的重要性；5)调查传播扩张中心下的Mor成熟度。更广泛的影响针对进入研究管道的每个阶段：外联将教育和参与更广泛的公众，并加强高中生进入地球科学专业的招聘。培训将通过巡游和课堂作业为本科生和研究生提供研究和教育机会。建立领导者网络将建立一支熟练的早期职业调查人员队伍，并生成一份用于规划OBS部署的开源手册。这项实验还将为国际太平洋阵列倡议做出贡献，并为全球和深部地幔断层扫描提供新的数据。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Seismic imaging of mid-ocean ridge systems at the Galápagos triple junctionA key element of plate tectonics is a ~50,000-km-long volcanic mountain chain circling the globe, where plates continuously separate and magma upwells from the Earth’s interior to cool. This has been understood for more than seventy years, but details of the deep structure of these systems remain unresolved. The problem is that most of these mountain chains lie under miles of water in the middle of the oceans (“mid-ocean ridges”; MORs). Seismological measurements are the main tool for peering tens of kilometres into the planet. This project involves a multi-year placement of ocean-bottom seismometers (OBSs) across and along two of these MORs, at a “triple-junction” location where three of these ridges meet. Seismic signals recorded by these instruments will be used to build 3-dimensional models of the solid Earth deep beneath the MORs. This project includes outreach and training activities. The project will involve high school students and will educate the public by producing films during the expeditions. It will provide research and education opportunities for undergraduate and graduate students through scientific expeditions and classwork. The program will involve early career investigators and generate an open-source manual for planning scientific expeditions at sea. The data will enhance understanding of geohazards and imaging of the entire planet.The ~50,000-km-long global mid-ocean ridge (MOR) system, the factory where 65% of the tectonic plates are generated, is arguably the defining feature of our planet’s surface. Yet, fundamental aspects of oceanic extension remain poorly understood, including the mechanisms driving upwelling at mid-ocean ridges and the origin of fabrics and discontinuities in mature ocean plates. This project involves a multi-year broadband ocean bottom seismometer (OBS) deployment across the Galápagos triple junction, involving two diachronous, overlapping ~40 station arrays spanning 400km along strike and perpendicular to the Pacific-Cocos and Cocos-Nazca spreading centers. Surface and body wave tomographic imaging of these MORs, including measurements of seismic attenuation, scattered phases, and seismic anisotropy will provide unprecedented spatial and methodological coverage of lithospheric and asthenospheric structure. This work will: 1) Test predicted signatures of dynamic upwelling; 2) Image MOR melt, dehydration, and shear structures that may persist in mature lithosphere; 3) Explore the 3-D organization of mantle flow beneath the ridges; 4) Exploit contrasts in spreading rate and ridge migration over underlying mantle to gauge the importance of these parameters on ridge dynamics; 5) Investigate MOR maturation beneath a propagating spreading center. Broader impacts target each stage of the pipeline into research: Outreach will educate and engage the broader public and enhance recruitment of high schoolers into the geoscience major. Training will provide research and education opportunities for undergraduate and graduate students through cruises and classwork. Building a Network of Leaders will establish a skilled cohort of early career investigators, and generate an open-source manual for planning OBS deployments. This experiment will also contribute to the international PacificArray initiative, and provide new data for global and deep mantle tomography.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.