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一些断层在大地震中会滑动，而另一些则不会。大洋变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--然而，人们对这些断层上的行为光谱知之甚少。这项研究将采用一系列技术来研究赤道大西洋的链变换断层，这是一个理想的地点，因为它具有可变的地震活动性和许多变换断层的典型的水深表达式。该项目将通过参加研究巡航及其对数据和样本的分析，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地球物理学虚拟课程，让更多的学生参与进来。大洋转换断层由在大地震中滑动的部分组成，这些部分被主要是无地震的部分隔开。大洋转换断层还表现出各种构造特征--山谷、横脊、中脊、花状构造、断层分段--它们的起源与应力、应变和材料性质有关。将使用两次巡航实验来探索这些断层动力学。朗塞斯号上的第一次巡航将收集多通道地震数据，并部署20台海底地震仪。一年后，第二次巡航将回收地震仪，部署自主水下机器人哨兵号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面观测与深层的地震约束联系起来。目标包括：·大大提高当前对缓慢滑动转换断层的理解。·从地震数据和哨兵微水深测量获得断层结构的地表到深度图像。·基于将微震活动模式和震源机制与断层结构联系起来，识别活动断裂带和活动隆起区。·破译断层耦合较差的部分是如何适应应变的，以及这些部分是否具有微震活动的特征，以及这些部分的深度是否像在快速滑动转换断层上观察到的那样，具有成群的微震活动特征。·利用样本、照片断面确定断裂带的主要岩性--包括隆起构造，·根据样本分析、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。·缓慢扩散转换中岩浆活动地点的定位，以及从岩浆成分评估来源可变性、熔融体系和储存深度。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。

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.