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

从2003年10月到2007年1月，研究人员在东太平洋隆起（EPR）北纬9°50°的Ridge 2000 Bull's Eye站点部署了一个海底地震仪网格，使用了一个4 × 4公里的12台仪器阵列，大约每年检索一次数据。这些数据为快速扩张脊的基本过程提供了令人兴奋的见解，包括火山作用和热液循环。它们还为了解该地点的地质、化学和生物数据提供了关键的联系。然而，根据该地区先前的结果，事件率比预期高出约2个数量级（记录的事件为32万起，预期为约4500起），因此，收集事件的初始拨款没有足够的预算用于处理和解释事件。此外，2006年初该地点的一次喷发又提供了大量数据，需要额外的资源来充分处理。该项目将继续这些努力，并将测试五个假设：1)下行流仍然集中在四阶偏移。2)轴向岩浆房深度和热液裂缝前缘在喷发前随时间保持稳定。3) 2006年1月22日的岩脉在9°50.5附近开始，然后向南开始，没有明显的迁移模式。(4)南北两段的喷发可能是对北纬9°50′集中喷发引起的应力变化的响应。热液细胞成像是流体化学和海底生物学变异性的基本驱动因素。更广泛的影响这个项目的主要好处之一是它对更广泛的社区的好处，特别是Ridge 2000团队工作的EPR“牛眼”。研究人员在向科学界和公众进行出色的外展方面有着令人印象深刻的记录，公众将继续参与这个项目。

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.