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自《2021年美国救援计划法案》(公法117-2)。该项目将使用数值模拟来研究控制海洋转换断层几何形状的过程。大洋转换断层是分布于全球大洋中脊系统的大型断层。已知转换断层会分裂、分割，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地点。拟议的研究将集中在岩浆供应对转换断层的寿命和几何形状的影响。将开发新的二维和三维模型，并将结果与地壳厚度的观测结果进行比较。项目成果将增进对大洋中脊新洋壳形成的控制以及对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)。它还将通过一个介绍性研讨会系列，向两个主办机构的本科生介绍海洋地球科学研究，帮助扩大未被充分代表的科学家对海洋地球科学的参与。拟议的工作假设，岩浆供应到转换内扩散中心是分段转换系统中扩展中心寿命的主要控制因素。随着岩浆供应的减弱，转换内区域的扩张将停止，先前分段的走滑断层将统一，无论由于板块运动的变化而施加的构造挤压或伸展。这一假设将通过一系列有限差分、单元标记、二维和三维数值构造模型进行研究，并受海底测深和重力异常观测的约束。在案例研究(Clarion FZ、St.Paul Tf和Gofar Tf)中，将根据断层和海底组构测量以及根据重力异常观测得出的地壳厚度估计，估计非活动断裂带和沿大洋中脊的活动转换断层上不断变化的岩浆扩张比例。根据观测约束，数值模拟中的岩浆供应将随着时间的推移而系统地减少，并记录变换断层形态的相应变化。变化的参数将包括扩展速率、原始转换断层错动的长度，以及转换内区域内岩浆与构造适应的扩展的比例。这项工作产生的3-D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优势和更广泛的影响审查标准进行评估，被认为值得支持。