Analysis of 9°50'N East Pacific Rise Seismicity: Insight into Hydrothermal and Magmatic Processes

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The investigators deployed an Ocean Bottom Seismometer grid from October 2003 until January 2007 at the Ridge 2000 Bull's Eye site at 9°50'N on the East Pacific Rise (EPR) using a 4 x 4 km array of 12 instruments with approximately annual data retrieval. These data provided exciting insights into fundamental processes at fast-spreading ridges including volcanism and hydrothermal circulation. They also provide critical linkages for understanding the geological, chemical and biological data at this site. However, event rates were ~2 orders of magnitude higher than anticipated based on prior results from this area (320,000 events recorded versus ~4,500 anticipated), and therefore the initial grant to collect them did not adequately budget for their processing and interpretation. In addition, an eruption at the site in early 2006 provided another flood of data that requires additional resources to adequately process.This project will continue those efforts and will test five hypotheses:1) Down-flow remains focused at 4th order off-set.2) The Axial Magma Chamber depth and hydrothermal cracking front remains stable with time leading up to an eruption.3) Diking on January 22nd 2006 is initiated near 9°50.5 but then initiates to the south without a distinct pattern of migration.4) Eruptions at segments to the north and south may have occurred in response to stress changes induced by the 9°50'N focused eruption.5) The hydrothermal cell imaged is a fundamental driver for variability in fluid chemistry and seafloor biology.Broader ImpactsOne of the main benefits of this project would be its benefit to the broader community, especially the Ridge 2000 team working EPR "Bulls-Eye". The investigators have an impressive record conducting excellent outreach to the scientific community as well as the general public, which will continue with this project.