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

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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.