Post-Eruption Seismic Monitoring at 9N: Toward Capturing a Full Volcanic Cycle

9N 喷发后地震监测：捕捉完整的火山周期

• 批准号: 0649538
• 负责人: Maya Tolstoy
• 金额: $ 10万
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-03-15 至 2009-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0649538&HistoricalAwards=false
• 关键词: Post; Eruption; Seismic; Monitoring; 9N

Two-thirds of the surface of our planet is formed at mid-ocean ridges, and yet the dynamics of this fundamental process are not well understood. From 2003-2006 the microearthquake character of the build-up to, and eruption associated with, a seafloor spreading event were recorded for the first time on ocean bottom seismometers. These data showed that there is a gradual build-up to an eruption, over several years, leading to the possibility that future eruptions may be predicted. Buried within the microearthquake data leading up to the eruption was exciting new insight into the structure of a full hydrothermal circulation cell. Hydrothermal circulation at mid-ocean ridges is responsible for 10% of global heat flux and 30% of the global heat flow anomaly. It also is significantly influences the chemistry of the lithosphere and overlying ocean, and supports extraordinary chemosynthetic biological communities. The data show that down-flow occurs on-axis and that fine scale segmentation of the seismicity matches fine scale segmentation of the chemistry and likely the magma body. In this project we will continue location and analysis of the microearthquake data leading up to the eruption, and specifically will look at how the seismicity of the hydrothermal cell changes with time. For instance, we hypothesize that the shape of the hydrothermal cell will stay essentially the same, but that the intensity of the seismicity will increase, particularly in areas close to the axial magma chamber as it nears eruption. We also hypothesize that the depth of seismicity associated with the axial magma chamber lid is unlikely to change with time until immediately prior to the eruption. Some studies have suggested that the magma chamber will shallow in the months or years preceding an eruption, but activity in the 2003-2004 deployment (2 years prior to the eruption) do not support this. By picking and locating the 100,000 microearthquakes recorded during the 2004-2005 deployment we will be able to identify any changes in the depth or character of the hydrothermal cell imaged in the 2003-2004 data. This research is fundamental to the character of seafloor spreading and to the nature of hydrothermal circulation at mid-ocean ridges. Our results will be of broad interdisciplinary value by linking to the other on-going studies at this site, and will help to shape a full integrated understanding of this section of mid-ocean ridge, from the mantle to the microbe, as outlined in the original Ridge 2000 science plan. The work has broader impacts in that it supports the training of graduate students, and a member of an underrepresented group (Tolstoy). Tolstoy, the lead-PI, also has a strong record of education and outreach work associated with this project including the Ridge 2000 distinguished lectureship, numerous lectures to school teachers and students, and participation in the educational film 'Aliens of the Deep'. Tolstoy anticipates continuing to do this type of outreach work, and is already committed to 3 educational presentations associated with this work in the coming months, including the PBS-Channel 13 'Celebration of Teaching and Learning' as an invited featured speaker in March 2007.

地球表面的三分之二是在大洋中脊形成的，但人们对这一基本过程的动力学还没有很好的了解。从2003年至2006年，海底地震仪首次记录了海底扩张事件的积聚和喷发的微地震特征。这些数据表明，火山爆发是在几年内逐渐积累起来的，这使得未来的火山爆发可能是可以预测的。在导致火山爆发的微地震数据中，隐藏着对完整热液循环细胞结构的令人兴奋的新见解。大洋中脊的热液环流对全球热通量的贡献率为10%，对全球热流异常的贡献率为30%。它还显著影响岩石圈和上覆海洋的化学，并支持非凡的化学合成生物群落。数据表明，下降流发生在轴上，地震活动的精细尺度分割与化学成分的精细尺度分割相匹配，可能是岩浆体。在这个项目中，我们将继续定位和分析导致喷发的微震数据，特别是将研究热液细胞的地震活动如何随时间变化。例如，我们假设热液池的形状将保持基本相同，但地震活动的强度将增加，特别是在靠近轴向岩浆房的地区，因为它接近喷发。我们还假设，与轴向岩浆房盖的地震活动的深度是不太可能随着时间的推移，直到即将爆发。一些研究表明，岩浆房在喷发前的几个月或几年内会变浅，但2003-2004年部署（喷发前2年）的活动并不支持这一点。通过挑选和定位2004-2005年部署期间记录的100 000次微震，我们将能够确定2003-2004年数据中成像的热液单元深度或特征的任何变化。这项研究对于海底扩张的性质和大洋中脊热液循环的性质具有根本意义。我们的研究结果将通过与该地点正在进行的其他研究联系起来，具有广泛的跨学科价值，并将有助于形成对大洋中脊这一部分的全面综合了解，从地幔到微生物，正如最初的脊2000年科学计划所概述的那样。这项工作具有更广泛的影响，因为它支持研究生的培训，以及一个代表性不足的群体（托尔斯泰）的成员。托尔斯泰，首席PI，也有一个良好的记录，教育和宣传工作与此项目相关，包括岭2000年杰出的讲师，许多讲座，学校教师和学生，并参与教育电影“外星人的深度”。托尔斯泰预计将继续做这种类型的推广工作，并已承诺在未来几个月内与这项工作相关的3个教育演讲，包括PBS-第13频道“教学和学习的庆祝活动”作为2007年3月的特邀演讲者。