OCE-PRF: Quantifying Magmatic Influences on the Longevity of Segmented Transform Fault Systems

OCE-PRF：量化岩浆对分段转换断层系统寿命的影响

• 批准号: 2126644
• 负责人: Thomas Morrow
• 金额: $ 30.7万
• 依托单位: Boston College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-09-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2126644&HistoricalAwards=false
• 关键词: OCE; PRF; Quantifying; Magmatic; Influences

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).The project will use numerical modeling to study the processes that control the geometry of oceanic transform faults. Oceanic transform faults are large faults that occur throughout the global mid oceanic ridge system. Transform faults are known to split, segment, and give rise to new volcanic spreading centers. These shifts can alter the locations where earthquakes are likely to occur on the seafloor. The proposed study will focus on the influence of magma supply on the longevity and geometry of transform faults. New 2-D and 3-D models will be developed, and results compared with observations of crustal thickness. Project results will improve the understanding of the controls on formation of new ocean crust on mid ocean ridges, and on the processes that drive seafloor earthquakes. The project will support an early career scientist (the PI/postdoc). It will also help broaden participation by underrepresented scientists in marine geosciences through an introductory seminar series that will introduce marine geoscience research to undergraduates at both host institutions.The proposed work hypothesizes that magmatic supply to an intra-transform spreading center is the primary control on spreading center longevity in a segmented transform system. As magmatic supply wanes, spreading in the intra-transform region will cease, and previously-segmented strike slip faults will unify, regardless of imposed tectonic compression or extension due to changing plate motions. The hypothesis will be investigated with a series of finite difference, marker-in-cell, 2-D and 3-D numerical tectonic models, constrained byseafloor bathymetry soundings and gravity anomaly observations. Changing magmatic proportions of spreading at both inactive fracture zones and active transform faults along mid-oceanic ridges in the case studies (Clarion FZ, St. Paul TF, and Gofar TF) will be estimated from fault and seafloor fabric measurements, coupled with crustal thickness estimates derived from gravity anomaly observations. Magmatic supply in the numerical simulations will be systematically decreased over time according to observational constraints and the responding changes in transform fault morphology will be recorded. Parameters varied will include the spreading rate, length of original transform fault offset, and the proportion of magmatic to tectonically-accommodated spreading within the intra-transform region. The 3-D model produced by this work will be publicly available for use by other researchers to expand upon this work.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.

该奖项的全部或部分资金来源于《2021 年美国救援计划法案》（公法 117-2）。该项目将使用数值模型来研究控制海洋转换断层几何形状的过程。大洋转换断层是遍布全球洋中脊系统的大型断层。众所周知，转换断层会分裂、分段并产生新的火山扩张中心。这些变化可能会改变海底可能发生地震的位置。拟议的研究将重点关注岩浆供应对转换断层的寿命和几何形状的影响。将开发新的 2-D 和 3-D 模型，并将结果与​​地壳厚度的观测结果进行比较。项目结果将增进对大洋中脊新洋壳形成的控制以及驱动海底地震的过程的理解。该项目将支持一名早期职业科学家（PI/博士后）。它还将通过介绍性研讨会系列帮助扩大海洋地球科学领域代表性不足的科学家的参与，该系列研讨会将向两个主办机构的本科生介绍海洋地球科学研究。拟议的工作假设向内部转换扩散中心提供岩浆是对扩散的主要控制分段变换系统中的中心寿命。随着岩浆供应的减弱，转换区内的扩散将停止，先前分割的走滑断层将统一起来，无论由于板块运动的变化而施加构造压缩或伸展。该假设将通过一系列有限差分、单元内标记、2D 和 3D 数值构造模型进行研究，并受到海底测深探测和重力异常观测的约束。在案例研究（Clarion FZ、St. Paul TF 和 Gofar TF）中，将通过断层和海底结构测量以及地壳厚度来估计沿大洋中脊的非活动断裂带和活动转换断层的岩浆扩展比例的变化根据重力异常观测得出的估计。根据观测限制，数值模拟中的岩浆供应将随着时间的推移系统地减少，并且将记录转换断层形态的响应变化。变化的参数包括扩张速率、原始转换断层偏移的长度以及转换区域内岩浆与构造适应扩张的比例。这项工作产生的 3D 模型将公开供其他研究人员使用，以扩展这项工作。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。