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: 2318853
• 负责人: Virginia Dorsey Wanless
• 金额: $ 48.51万
• 依托单位: Boise State University
• 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=2318853&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断层的某些部分会在大地震中滑动，而其他断层部分却不会因为其简单的组成和可预​​测的运动而成为研究断层滑动的理想选择 - 但这些断层的行为谱。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，由于其多变的地震活动及其典型的许多转换断层的测深表达，该断层是一个理想的地点。职业科学家通过参与研究航行以及对数据和样本的分析，将让更多的学生参与有关海洋地质学和地球物理学的多机构虚拟课程，该课程由滑入的部分组成。由主要是抗震断层的部分分隔开的大地震也显示出各种结构特征——山谷、横脊、中脊、花状结构、断层分段——其起源与应力、应变和物质有关。 R/V Langseth 上的第一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，并利用疏浚对活动断层带进行采样。这些数据集将断层结构和成分的表面观测结果与深度地震约束联系起来。大幅推进当前对慢滑移转换断层的认识。• 通过地震数据和 Sentry 微测深技术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活动断层相联系来识别活动断层带和活动隆起区域断层结构。• 破译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群的特征，正如在更快滑动转换断层中所观察到的那样。• 使用样本、照片横断面和地震速度确定断层带（包括隆起结构）中的主要岩性。• 阐明流体在改变断层滑动行为中的作用，基于样本分析、化学传感器数据集、地震速度变化和微震分布。• 缓慢扩散变换中磁活动地点的位置以及震源变异性的评估，该奖项反映了 NSF 的法定使命，并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，被认为值得支持。