Determining the origin of Haxby lineaments using magnetotelluric and bathymetric data

使用大地电磁和测深数据确定哈克斯比轮廓的起源

• 批准号: 2211895
• 负责人: David Sandwell
• 金额: $ 78.15万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-09-01 至 2025-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2211895&HistoricalAwards=false
• 关键词: Determining; origin; Haxby; lineaments; using

An unsolved mystery of the deep ocean seafloor is the presence of regular, wave-like fluctuations in the strength of Earth’s gravity above the seafloor. These features repeat over regular intervals and can be clearly detected by satellites orbiting the Earth. There are three theories for the processes forming the gravity fluctuations: seafloor cracking as ocean crust moves away from mid-ocean ridges and cools, mantle convection cells, or melt channels beneath the crust. This project will find out which of these theories is correct - or perhaps discover the answer is something altogether unexpected - by acquiring geophysical data at a region in the Pacific Ocean where the gravity features are particularly prominent. Regardless of what is causing the gravity fluctuations, the answer will reveal more about the dynamics of our planet beneath the oceans and how plate tectonics works.The objective of this study is to determine the origin of Haxby lineaments which are small, periodic undulations in the gravity field above oceanic lithosphere that, despite decades of study, remain mysterious. This project will deploy 40 ocean-bottom broadband magnetotelluric instruments to measure variations in mantle conductivity in the lithosphere and asthenosphere, and will map the seafloor topography and sonar backscatter, in a 200 km by 600 km area northeast of the Marquesas Islands in the Pacific Ocean basin. By correlating conductivity, bathymetry, and gravity, the project will be able to distinguish between multiple competing models attempting to explain the Haxby lineaments. The proposed experiment would effectively discriminate between three hypotheses: thermal contraction of the lithosphere, small-scale convection in the asthenosphere, and asthenospheric return flow channels. The thermal contraction model predicts that bathymetry should be positively correlated with the gravity rolls without an asthenospheric component. The small-scale convection and return flow channels models suggest an asthenospheric source of the gravity lineaments - hot, low-density mantle detectable by magnetotelluric data - but differ in how the conductivity anomalies correlate to topography and gravity. The results will help determine the nature of lithosphere-asthenosphere dynamics far from ridges or subduction zones, including whether there is partial melt beneath older lithosphere (42 Ma).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

深海海底的一个未能解决的奥秘是在海底上方地球重力的强度中存在常规的，类似波浪状的波动。这些特征在定期间隔内重复，可以通过绕地球绕的卫星清楚地检测到。有三种形成重力波动的过程的理论：海底开裂时，海壳从外壳中部山脊和冷却，地幔连接细胞或熔体下方的融化通道移开。该项目将通过在太平洋地区的一个区域中获取地球物理数据，从而发现这些理论中的哪种是正确的 - 或者发现答案是完全出乎意料的 - 重力特征特别突出。无论导致重力波动的是什么，答案都将更多地揭示我们的星球下海洋下的动态以及板块构造的工作原理。这项研究的目的是确定在海洋岩石圈以上的重力场中的小小的，周期性的小小的起源，这是海洋性岩石圈以上的重力，仍然是神秘的，仍然是神秘的。该项目将部署40个海洋宽带磁铁磁铁仪器，以衡量岩石圈和软圈中地幔电导率的变化，并将在太平洋海盆中Marquesas群岛东北地区的200 km of Seaforor Topography和Sonar Backscatter中绘制海底地形和声纳反向散射。通过将电导率，测深和重力相关联，该项目将能够区分试图解释Haxby谱系的多个竞争模型。提出的实验将有效地区分三个假设：岩石圈的热收缩，小层中的小规模转化率和动态圈的回流流通道。热收缩模型预测，测深量应与不动性磷酸成分的重力卷呈正相关。小尺度的转换和返回流通道模型提出了重力谱系的动荡源 - 热，低密度的地幔可通过磁铁数据检测到 - 但在电导率异常与地形和重力相关的方式方面有所不同。结果将有助于确定岩石圈 - 心理圈动力学的性质，远离脊或俯冲带，包括在较旧的岩石圈下是否有部分融化（42 MA）。该奖项反映了NSF的法定任务，并被认为是通过使用基金会的智力和更广泛影响的评估来审查CRITERIA的评估来通过评估来获得的支持。