Collaborative Research: Chain Transform Fault: Understanding the dynamic behavior of a slow-slipping oceanic transform system

地球科学的一个长期目标是了解为什么断层的某些部分在大地震中滑动，而其他部分则没有。海洋转换断层由于其简单的组成和可预测的运动是研究断层滑动的理想选择，但对这些断层的行为谱却知之甚少。这项研究将采用一系列技术来研究赤道大西洋的链式转换断层，这是一个理想的地点，因为它的地震活动多变，而且它的测深表现是许多转换断层的典型特征。该项目将通过参加研究航行和分析数据和样本，培训跨学科海洋科学方面的早期职业科学家。将通过一个多机构的海洋地质学和海洋物理学虚拟课程，吸引更多的学生参加。海洋转换断层由在大地震中滑动的部分组成，这些部分被主要是地震的部分分开。海洋转换断层也显示出各种各样的结构特征--山谷、横脊、中脊、花状构造、断层分段--其成因与应力、应变和材料性质有关。一个两个巡航实验将被用来探测这些故障动态。Langseth号研究船的首次巡航将收集多通道地震数据，并部署20个海底地震仪。一年后，第二次巡航将恢复地震仪，部署自主水下航行器哨兵进行高分辨率地球物理调查，并使用疏浚对活动断层带进行采样。这些数据集将把断层结构和组成的地面观测与深度的地震约束联系起来。目标包括：·实质性地推进目前对缓慢滑动转换断层的理解。从地震数据和Sentry微水深测量获得的断层结构的地表到深度图像。·根据微震活动模式和震源机制与断层结构的联系，识别活动断层链和活动隆起区域。·解读断层耦合不良部分如何适应应变，以及这些部分是否以及在什么深度具有微震活动群的特征，就像在快速滑动转换断层中观察到的那样。利用样品、照片断面和地震速度确定断裂带（包括隆起构造）的主要岩性。·基于样本分析、化学传感器数据集、地震速度变化和微震活动性分布，阐明流体在改变断层滑动行为中的作用。·在缓慢扩散转化中岩浆活动地点的位置，以及来源变异性、熔融系统学和岩浆成分储存深度的评估。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

A longstanding goal of Earth Science is to understand why some sections of faults slip in large earthquakes while other sections do not. Oceanic transform faults are ideal for studying fault slip due to their simple composition and predictable motion - yet the spectrum of behavior on these faults is poorly understood. This study will employ a range of techniques to study the Chain transform fault in the equatorial Atlantic, which is an ideal locality due to its variable seismicity and its bathymetric expression that is typical of many transform faults. This project will train early career scientists in interdisciplinary marine science through their participation in research cruises and their analyses of data and samples. A broader cross-section of students will be engaged through a multi-institution virtual course on marine geology and geophysics. Oceanic transform faults consist of sections that slip in large earthquakes separated by sections that are primarily aseismic. Oceanic transform faults also display a variety of structural features – valleys, transverse ridges, median ridges, flower structures, fault segmentation – whose origins are linked to stress, strain, and material properties. A two-cruise experiment will be used to probe these fault dynamics. The first cruise aboard the R/V Langseth will collect multi-channel seismic data and deploy 20 ocean bottom seismometers. A year later, a second cruise will recover seismometers, deploy the autonomous underwater vehicle Sentry for high-resolution geophysical surveys, and use dredging to sample the active fault zone. These datasets will connect surface observations of fault structure and composition to seismic constraints at depth. Goals include:• Substantially advancing current understanding of slow-slipping transform faults.• Surface-to-depth images of fault structures from seismic data and Sentry micro-bathymetry.• Identification of active fault strands and areas of active uplift based on linking microseismicity patterns and focal mechanisms to fault structures.• Deciphering how strain is accommodated on poorly coupled portions of the fault, and whether, and at which depth, those portions are characterized by swarms of microseismicity, as has been observed at faster slipping transform faults.• Determination of the dominant lithologies in the fault zone—including in uplifted structures—using samples, photo transects, and seismic velocity.• Elucidation of the role of fluids in modifying fault-slip behavior, based on sample analyses, chemical-sensor datasets, seismic-velocity variations, and microseismicity distribution.• Location of sites of magmatic activity within a slow spreading transform and evaluation of source variability, melting systematics, and storage depths from magma compositions.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.