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

合作研究：链变换断层：了解慢滑海洋变换系统的动态行为

• 批准号: 2318855
• 负责人: Mark Behn
• 金额: $ 40.34万
• 依托单位: Boston College
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-02-01 至 2028-01-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2318855&HistoricalAwards=false
• 关键词: Collaborative; Research; Chain; Transform; Fault

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.

地球科学的一个长期目标是了解为什么在大地震中有些断层会滑动，而另一些则不会。海洋变换断层是研究断层滑动的理想选择，因为它们组成简单，运动可预测，但人们对这些断层的行为谱知之甚少。本研究将采用一系列技术对赤道大西洋的链变换断层进行研究，由于该断层的地震活动性变化较大，其水深表达是许多转换断层的典型特征，因此是一个理想的位置。这个项目将通过参加研究巡航和对数据和样本的分析，培养跨学科海洋科学方面的早期职业科学家。更广泛的学生将通过多机构的海洋地质学和地球物理学虚拟课程参与。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。海洋转换断层还表现出山谷、横脊、中脊、花状构造、断层分割等多种构造特征，其起源与应力、应变和材料性质有关。一个双巡航实验将用于探测这些断层动力学。朗塞斯号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裂带进行采样。这些数据集将把断层结构和组成的地表观测与深度地震约束联系起来。目标包括：•实质性地推进当前对慢滑变换断层的理解。•从地震数据和Sentry微测深技术中获得断层结构的地表到深度图像。•通过将微震活动模式和震源机制与断层结构联系起来，识别活动断层链和活动隆起区域。•破译应变是如何在断层的低耦合部分上调节的，以及这些部分是否具有微震活动群，以及在哪个深度，就像在快速滑动变换断层中观察到的那样。•利用样品、照片样带和地震速度确定断裂带（包括隆升构造）的主要岩性。•基于样品分析、化学传感器数据集、地震速度变化和微震活动分布，阐明流体在改变断层滑动行为中的作用。•岩浆活动地点的位置在一个缓慢的扩展转换和评估来源的可变性，熔融系统，并从岩浆成分的储存深度。该奖项反映了美国国家科学基金会的法定使命，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。