Establishing a Long-Term Geodetic Network at the East Pacific Rise Ridge 2000 Integrated Studies Site

在东太平洋海隆 2000 综合研究站点建立长期大地测量网络

• 批准号: 1342908
• 负责人: Scott Nooner
• 金额: $ 2.39万
• 依托单位: University of North Carolina at Wilmington
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-04-01 至 2014-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1342908&HistoricalAwards=false
• 关键词: Establishing; Long; Term; Geodetic; Network

Abstract Most of the world's plate boundaries are submerged beneath the oceans, and little is known about how these boundaries accommodate plate motion on monthly to yearly time scales. At mid-ocean ridges, new oceanic crust is formed as two oceanic plates move apart and magma is tapped from mantle upwelling beneath the ridge. Magma movement beneath active volcanoes on land has been tracked using a variety of geodetic techniques such as GPS and InSAR, however, to date there are few constraints on magma extraction beneath mid-ocean ridges. Lenses of melt (magma) have been identified both within the crust and at the crust mantle boundary, as well as a low seismic velocity mush (partial melt) zone beneath the crustal magma lens. Eruptions at the ridge crests presumably tap into these melt lenses but the fundamental scales associated with magma movement beneath ridge crests remain obscure. The questions to be addressed in this study include 1) What volume of the crustal melt lens is tapped by an eruption? How quickly does the melt lens get replenished from upwelling mantle? Does an eruption depend on horizontal transport of magma in a shallow dike? 2.) What is the rheologic structure of the ridge, including the width of the low viscosity mush zone? What is the mechanical behavior of the crust during and after an eruption? 3.) Do vents change temperature, chemistry flow rates, and location as the underlying magma lens evolves?We plan to address these questions by monitoring the vertical displacements of the seafloor at 9degrees50'N on the EPR in the vicinity of an eruption that occurred in early 2006. We will use a Mobile Pressure Recorder (MPR) in three campaign style surveys to measure the relative water pressure between different seafloor locations to determine changes in the relative elevation of benchmarks placed on the seafloor. Due to the buoyancy of the magma, surface deformation directly reflects the movement of magma below the surface. We expect to track the gradual movement of magma between eruption and diking events. We plan to compare processes under this fast-spreading ridge segment, which is underlain by a continuous, linear body of melt, to that of volcanoes elsewhere, which typically have a focused magma source. The temporal and spatial scales of recharging of the magma chamber post eruption will depend on the physical characteristics of the underlying mush zone and provide insight into the rheology of the surrounding crust. When paired with the co-located array Bottom Pressure Recorders (BPR) to be deployed in February 2007, both episodic and long-term deformation information will be available, tracking magma movements with hourly to yearly time scales. This will allow us, in collaboration with other researchers, to examine system relationships, such as the interplay between movements of magma, changes in hydrothermal vent systems, and microseismicity.Broader impacts This work will establish the infrastructure for long-term geodetic monitoring and begin accumulating a geodetic time series. All aspects of the ridge system are influenced or driven by the heat from magma that moves within the Earth's crust, which makes this work important in understanding all ridge systems and processes. Borrowing an instrument from Dr. Zumberge will promote collaboration between our two institutions. Public dissemination of the work will take place through peer reviewed publications and presentations at scientific conferences, interdisciplinary meetings, and seminars at other universities. We will work with the Ridge 2000 Education and Outreach office to educate the public about the significance of this project in understanding ridge systems, and how this work fits into the larger picture.

抽象的大多数板块边界都被淹没在海洋下方，对于这些边界如何每月至年度时间尺度容纳板块运动，几乎不知道。在海洋中部山脊上，新的海洋外壳形成，两个海洋盘子分开，岩浆从山脊下方的地幔上升的地幔上挖掘出来。 在陆地上有活跃火山下方的岩浆运动已经使用了多种大地GP和INSAR进行跟踪，但是，迄今为止，在海洋山脊下方的岩浆提取上几乎没有限制。 在地壳和地壳边界内已经确定了熔体（岩浆）的透镜（岩浆），以及在地壳岩浆镜头下方的低地震速度糊状（部分熔体）区域。 山脊上的爆发大概可以挖掘出这些熔体镜头，但与山脊冠下面的岩浆运动相关的基本尺度仍然晦涩难懂。本研究中要解决的问题包括1）喷发敲击了什么体积的地壳融化镜头？从上升的地幔中补充熔体镜头的速度如何？爆发是否取决于浅堤中岩浆的水平运输？ 2.）山脊的流变结构是什么，包括低粘度糊状区的宽度？ 爆发期间和之后地壳的机械行为是什么？ 3.）通风孔是否会随着潜在的岩浆镜头的发展而改变温度，化学流量和位置？我们计划通过监视9级海底的垂直位移来解决这些问题。位于海底的基准的相对升高。 由于岩浆的浮力，表面变形直接反映了表面下方的岩浆运动。 我们希望在喷发和堤防事件之间跟踪岩浆的逐步运动。 我们计划将这个快速扩张的山脊段下的工艺与其他地方的火山的连续，线性熔体的体系相比，该过程通常具有聚焦的岩浆来源。 喷发后岩浆腔室充电的时间和空间尺度将取决于基础糊状区的物理特征，并洞悉周围地壳的流变学。 当与2007年2月部署的共同定位的阵列底部压力记录器（BPR）配对时，将提供情节和长期变形信息，以每小时至年度时间尺度跟踪岩浆运动。 这将使我们与其他研究人员合作研究系统关系，例如岩浆运动，水热系统的变化和微震震性之间的相互作用。Broader对这项工作的影响将建立长期地球测量监测的基础设施，并开始累积地球时间序列。 山脊系统的所有方面都受到岩浆在地壳内移动的热量的影响或驱动，这使得这项工作对于理解所有山脊系统和过程都很重要。从Zumberge博士那里借来的乐器将促进我们两个机构之间的合作。 公众对这项工作的传播将通过在科学会议，跨学科会议和其他大学的研讨会上进行的同行审查的出版物和演讲进行。 我们将与Ridge 2000教育和外展办公室合作，向公众教育该项目在理解山脊系统方面的重要性，以及该工作如何适合大局。