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

调查人员从2003年10月至2007年1月在东太平洋海隆（EPR）北纬9° 50 '的山脊2000牛眼站点部署了一个海底地震计网格，使用了一个由12台仪器组成的4x4公里阵列，大约每年进行一次数据检索。这些数据提供了令人兴奋的见解，在快速扩张的山脊，包括火山活动和热液循环的基本过程。它们还为了解该场址的地质、化学和生物数据提供了重要的联系。然而，事件发生率比基于该领域先前结果的预期高出约2个数量级（记录的事件为320，000起，预期约为4，500起），因此收集这些事件的初始拨款没有为它们的处理和解释提供足够的预算。此外，2006年初该地点的一次火山爆发提供了另一批数据，需要额外资源才能充分处理，本项目将继续这些努力，并将检验五个假设：1）向下流动仍然集中在四阶偏移。2）轴向岩浆室深度和热液裂解前沿随着时间的推移保持稳定，导致爆发。3）2006年1月22日的筑堤开始于9°50.5附近，但随后开始向南移动，没有明显的迁移模式。4）北部和南部部分的喷发可能是对9° 50 'N集中喷发引起的应力变化的响应。成像的热液池是流体化学和海底生物学变化的基本驱动力。更广泛的影响该项目的主要好处之一是它将有利于更广泛的社区，特别是岭2000年小组工作EPR“靶心”。 研究人员在与科学界和公众进行良好的外联方面有着令人印象深刻的记录，这将继续进行这一项目。

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.