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

该奖项全部或部分由2021年美国救援计划法案（公法117-2）资助。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。大洋转换断层是发生在全球大洋中脊系统的大型断层。转换断层已知会分裂、分割，并产生新的火山扩张中心。这些变化可以改变海底可能发生地震的位置。建议的研究将集中在岩浆供应的寿命和几何形状的转换断层的影响。将开发新的二维和三维模型，并将结果与地壳厚度观测结果进行比较。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。该项目将支持早期职业科学家（PI/博士后）。它还将有助于扩大参与海洋地球科学的代表性不足的科学家通过介绍性的研讨会系列，将介绍海洋地球科学研究的本科生在两个主办institutions.The拟议的工作假设，岩浆供应到一个内部转换扩展中心是主要的控制扩展中心寿命在一个分段的转换系统。随着岩浆供应的减少，内部转换区域的扩张将停止，先前分段的走滑断层将统一，而不管由于不断变化的板块运动而施加的构造压缩或伸展。将利用一系列有限差分、单元格内标记、二维和三维数值构造模型，并在海底测深和重力异常观测的约束下，对这一假设进行研究。在案例研究（克拉里昂断裂带、圣保罗断裂带和戈法尔断裂带）中，沿着沿着大洋中脊的不活跃断裂带和活跃转换断裂带不断变化的岩浆扩散比例，将根据断层和海底组构的测量结果，以及根据重力异常观测得出的地壳厚度估计值进行估算。根据观测约束条件，数值模拟中的岩浆供应将随着时间的推移而系统地减少，转换断层形态的相应变化将被记录下来。变化的参数将包括扩展速率，原始转换断层偏移的长度，以及内部转换区域内岩浆与构造调节扩展的比例。这项工作产生的三维模型将公开提供给其他研究人员使用，以扩大这项工作。该奖项反映了NSF的法定使命，并已被认为是值得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的支持。

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.