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

2003年10月至2007年1月，调查人员在东太平洋海隆(EPR)北纬9°50‘处的Ridge 2000 Bull’s Eye站点部署了海底地震仪网格，使用由12台仪器组成的4x4公里阵列，大约每年提取一次数据。这些数据为快速扩张的海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。它们还为理解该地点的地质、化学和生物数据提供了关键联系。然而，事故率比基于该领域先前结果的预期高出约两个数量级(记录的事件为32万次，而预期为~4500次)，因此，最初用于收集这些事件的赠款没有足够的预算用于处理和解释这些事件。此外,2006年初的一次喷发提供了另一批数据，需要额外的资源才能充分处理。该项目将继续这些努力，并将检验五个假设：1)下降流仍然集中在4级偏离2)轴向岩浆室深度和热液裂解前沿保持稳定，随着时间的推移，导致喷发。3)2006年1月22日的脉动开始于9°50.5附近，但随后向南开始，没有明显的迁移模式。4)南北部分的喷发可能是对9°50‘N集中喷发所引起的应力变化的响应.5)所成像的热液单元是流体化学和海底生物可变性的根本驱动力。广泛影响该项目的主要好处之一将是它对更广泛的社区的好处，尤其是Ridge 2000团队正在工作的EPR《靶心》。调查人员在与科学界和普通公众进行良好接触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.