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

Galápagos三重交界处洋中脊系统的地震成像板块构造的一个关键要素是环绕地球的约5万公里长的火山山脉链，在那里板块不断分离，岩浆从地球内部上涌冷却。这已经被理解了70多年，但这些系统的深层结构细节仍然没有解决。问题是这些山脉大多位于海洋中央数英里的水下（“洋中脊”；MORs）。地震测量是观测地球几十公里深处的主要工具。该项目涉及在其中两个MORs上放置海底地震仪（OBSs），这些MORs位于其中三个山脊交汇的“三重交界处”。这些仪器记录的地震信号将用于建立MORs深层固体地球的三维模型。该项目包括外联和培训活动。该项目将由高中生参与，并将在探险期间制作电影，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。该项目将包括早期职业调查人员，并为规划海上科学考察生成一份开源手册。这些数据将加强对地质灾害的了解，并对整个地球进行成像。大约5万公里长的全球洋中脊（MOR）系统是65%的构造板块产生的工厂，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，包括驱动洋中脊上升流的机制以及成熟海洋板块的结构和不连续的起源。该项目涉及横跨Galápagos三重连接点的多年宽带海底地震仪（OBS）部署，涉及两个跨时，重叠的约40个站点阵列，沿走向跨越400公里，垂直于太平洋-科科斯和科科斯-纳斯卡传播中心。这些MORs的表面和体波层析成像，包括地震衰减、散射相位和地震各向异性的测量，将为岩石圈和软流圈结构提供前所未有的空间和方法覆盖。本工作将：1)测试动态上升流的预测特征；2)成像成熟岩石圈中可能存在的熔融、脱水和剪切构造；3)探索脊下地幔流动的三维组织；4)利用扩展速率和脊向下地幔迁移的对比来衡量这些参数对脊动力学的重要性；5)研究在繁殖扩散中心下的more成熟。更广泛的影响目标是研究管道的每个阶段：外展将教育和吸引更广泛的公众，并加强高中学生进入地球科学专业的招聘。培训将通过游轮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个有技能的早期职业调查者队伍，并为规划OBS部署生成一个开源手册。该实验还将为国际太平洋阵列计划做出贡献，并为全球和深部地幔层析成像提供新的数据。该奖项反映了美国国家科学基金会的法定使命，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。

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.