Exploring submarine slope failures with seismic data and physical laboratory experiments

海底斜坡破坏发生在世界各地的边缘地带，并可能导致当地和遥远海岸的破坏性海啸。来自被动大陆边缘的地球物理数据（测深和地震）证明，这些断层从薄（小于1米）到厚（大于100米）不等，可能移动了数百公里，表现得像流体或固体。这些分析与海底边坡破坏的数值模型相结合表明，当浅埋沉积物受到外部应力（如流体压力变化或与地震有关的震动）的扰动时，就会触发破坏。现有的钻孔样本和地球物理数据提供了物质破坏后的快照，数值模型提供了破坏如何开始的预测，但缺乏对影响最终矿床的破坏过程的直接观察。该项目将利用北美边缘社区地震实验的现有数据来描述北卡罗来纳州近海的失效沉积。将建立一个具有新型触发机制的缩放物理模型，以创建和可视化故障动力学。该项目将推进基于过程的建模技术，将初始条件、启动机制和失效行为联系起来。作为该项目更广泛影响的一部分，研究生将接受跨学科（地震学、沉积学、地质力学和工程学）的培训。总体而言，该项目将通过改善美国海岸线边坡失效和海啸产生的风险评估，为社会做出贡献。该项目将把由美国地质与地球科学研究所资助的北美东部边缘社区地震实验的现有现场数据与实验室和数值模型相结合，从而对边坡破坏进行基于过程的分析，将破坏类型和动力学与初始条件和驱动机制（包括地震震动和流体压力变化）联系起来。实验室实验将提供对初始条件（沉积物类型和性质）、流体压力（震级和分布）和震源（位置和能量）的控制，同时启动边坡破坏并观察破坏动力学。数值模式将模拟自然界中观察到的过程，并提供一种将实验室规模的实验与现场规模的观察联系起来的方法。该项目将解决以下假设：1)海底斜坡破坏沉积物内的地震速度剖面与相邻未破坏沉积物之间的差异记录了不同的有效应力和强度剖面；2)破坏开始时沉积物的有效应力和强度影响破坏的海底沉积物的边坡破坏类型和动员行为；3)坡体失稳触发机制影响坡体失稳动力学和演化，进而影响坡体失稳发生海啸的潜力。整个项目的目标是描述和描述破坏类型、沉积物、初始条件和驱动机制之间的联系，这将提高利用沉积记录中的斜坡破坏沉积物来评估驱动机制的能力。这将提高我们了解坡损的历史和分布及其海啸潜力的能力。该项目还将对可能产生大海啸的条件提供限制，这可以为边坡破坏和相关海啸危害的风险评估提供信息。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。

Submarine slope failures occur on margins worldwide and can lead to damaging tsunamis both locally and on distant shores. Geophysical data (bathymetric and seismic) from passive continental margins document that these failures range from thin (less than 1 m) to thick (greater than 100 m) units, may have moved 100s of km, and can behave like a fluid or a solid. These analyses combined with numerical models of submarine slope failures suggest the failures are triggered when shallowly buried sediments are perturbed by an external stress such as a change in fluid pressure or earthquake-related shaking. Existing borehole samples and geophysical data provide a snapshot of what the materials look like after failure and numerical models provide predictions of how failures started, yet there is a lack of direct observations of the failure process which affects the final deposits. This project will characterize failure deposits offshore North Carolina using existing data from the North American Margin Community Seismic Experiment. A scaled, physical model with a novel triggering mechanism will be built to create and visualize failure dynamics. The project will advance process-based modeling techniques to incorporate how initial conditions, initiation mechanism, and failure behavior are linked. As part of the broader impacts a graduate student will be trained across multiple disciplines (seismology, sedimentology, geomechanics and engineering) as part of this project. Overall, the project will contribute to society by improving risk assessment for slope failures and tsunami generation along the US coastline. This project will integrate existing field data from the GeoPRISMS-funded Eastern North American Margin Community Seismic Experiment with laboratory and numerical models allowing for a process-based analysis of slope failures that links failure type and dynamics to initial conditions and driving mechanisms including earthquake shaking and fluid pressure changes. Laboratory experiments will provide a control on initial conditions (sediment type and properties), fluid pressures (magnitudes and distribution), and earthquake sources (location and energy) while initiating slope failures and observing failure dynamics. Numerical models will simulate the processes observed in nature and provide a means to link lab-scale experiments with field-scale observations. The project will address the following hypotheses: 1) differences between seismic velocity profiles within submarine slope failure deposits and adjacent, unfailed deposits record different effective stress and strength profiles; 2) effective stress and strength of sediments at the onset of failure impact the slope failure type and mobilization behavior of failed submarine sediments; and 3) slope failure trigger mechanism impacts slope failure dynamics and evolution, which influences their tsunami-generating potential. The overall project objective is to describe and characterize links between failure type, deposits, initial conditions, and driving mechanisms, which will increase the ability to use slope failure deposits in the sedimentary record to evaluate driving mechanisms. This will improve our ability to understand the history and distribution of slope failures and their tsunami potential. The project will also provide constraints on conditions that may produce large tsunami, which can inform risk assessment for slope failure and associated tsunami hazard.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.