CAREER: Microfossils as Drivers for Submarine Landslides?

水下山体滑坡是具有潜在社会和社会经济后果的自然灾害。山体滑坡在全球范围内发生，可能引发海啸，并对人们和基础设施构成威胁，特别是在沿海地区。为了减少这种对人类和基础设施的影响，提高我们对海洋沉积物中斜坡稳定性的理解是至关重要的。该项目侧重于通常不会发生地震的大陆边缘地区，因此不会引发山体滑坡。在这些地点，目前尚不清楚生活在海洋中并最终进入海洋沉积物中的微生物的骨骼残骸如何潜在地削弱这些沉积物，并使其成为破坏和水下山体滑坡的先决条件。教育活动的目标是为高中生、本科生和研究生提供高影响力的学习经验和研究机会。该项目面向在没有地球科学课程要求的德克萨斯州STEM领域，即地球科学领域，代表人数不足的群体的学生。这将通过与当地布莱恩高中每年定期举行的教育计划来实现，该计划包括课堂访问、为期一天的研讨会和为期两周的暑期研究活动。将开发一门本科生和研究生课程，其中包括一次前往德克萨斯州西部和新墨西哥州的国内实地考察，以研究海底斜坡水道和滑坡沉积。通过所有组成部分，该项目将培养能够促进跨学科科学和广泛合作的下一代研究人员，以促进知识的发展和减轻自然灾害。该研究项目结合了实验和数值努力，旨在表征微化石在形成薄弱层中的作用，这些薄弱层可能成为海底滑坡的大规模滑动面。在这个项目中，海洋沉积物将在不同的浓度和可重复的条件下系统地与硅藻土混合。研究的目标是确定关键的微化石密度与门槛行为，在沉积物包内的准确位置，以及在富含微化石的软弱层内或之上可能诱发超压和引发广泛破坏的埋藏条件。因此，这项拟议的研究不仅将提供对富含微化石的沉积物的斜坡破坏机制的见解，还将有助于从岩心识别潜在的未来滑动面和/或记录来自海底和湖泊环境的数据，在这些环境中，滑坡可能在没有地震等外部触发因素的情况下发生。为了记录富含微化石的海洋沉积物的力学、水力和剪切特性，将在对应于常见滑坡起始深度的有效应力下进行单轴再沉积和恒定应变固结以及直剪和三轴剪切试验。通过将变形实验的流体力学数据分析与微观成像观测相结合，将对微观结构变化、微化石变形和剪切破坏面的发育进行定性和定量描述。数值斜坡稳定性模型将为提升测量属性和引入非均质分层系统提供洞察，这些系统分析富含微化石的薄弱层与过度和潜在的非生物沉积之间的相互作用。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。

Underwater landslides are natural hazards with potential societal and socioeconomic consequences. Landslides occur globally, can cause tsunamis, and pose threats to people and infrastructure, especially near coasts. To reduce this impact on people and infrastructure, it is critical to advance our understanding of slope stability in ocean sediments. This project focuses on continental margins where earthquakes typically do not occur, and as such, do not act as triggers for landslides. In these sites, it remains unclear how the skeletal remains of microorganisms that live in the ocean and end up in ocean sediments could potentially weaken and precondition those sediments for failure and underwater landslides. The goal of the education activities is to provide high impact learning experiences and research opportunities for high school, undergraduate, and graduate students. This project is geared towards students from underrepresented groups in a STEM field, namely geosciences, in Texas, which lacks Earth science curriculum requirements. This will be achieved through an annually recurring education program with the local Bryan High School consisting of classroom visits, a one-day workshop, and two-week summer research activity. An undergraduate and graduate student course will be developed, which includes a domestic field trip to West Texas and New Mexico to study submarine slope channels and landslide deposits. Through all components, this project will foster next-generation researchers who can facilitate interdisciplinary science and broad collaboration to advance knowledge and mitigate natural hazards.This research project integrates experimental and numerical efforts and aims to characterize the role of microfossils in generating weak layers, which could become large-scale glide planes for submarine landslides. In this project, marine sediments will be systematically mixed with diatomite in varying concentrations and under repeatable conditions. The research goals are to determine key microfossil concentrations with threshold behavior, exact location within the sediment package, and burial conditions under which overpressure may be induced and wide-spread failure initiated within or above a microfossil-rich weak layer. Therefore, this proposed research will not only provide insights into slope failure mechanisms for microfossil-rich sediments but will also help in identifying potential future glide planes from cores and/or logging data from submarine and lacustrine settings where landslides may occur without external triggers like earthquakes. To document mechanical, hydraulic, and shear properties of microfossil-rich marine sediments, uniaxial resedimentation and constant rate of strain consolidation, as well as direct shear and triaxial shear experiments will be conducted at effective stresses corresponding to common landslide initiation depths. Microstructural changes, microfossil deformation, and development of shear failure planes will be qualitatively and quantitatively characterized by integrating analysis of hydromechanical data from deformation experiments with microscale imaging observations. Numerical slope stability models will provide insights into upscaling measured properties and introducing heterogeneous layered systems that analyze the interaction between microfossil-rich weak layers with over-and underlying non-biogenic sediments.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.