Exploring submarine slope failures with seismic data and physical laboratory experiments

海底斜坡坍塌发生在世界各地的边缘，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，这些断层的范围从薄(不到1米)到厚(大于100米)，可能移动了数百公里，可以表现为流体或固体。这些分析结合海底斜坡破坏的数值模型表明，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，海底斜坡破坏就会触发。现有的钻孔样本和地球物理数据提供了失效后材料外观的快照，数值模型提供了失效开始方式的预测，但缺乏对影响最终沉积的失效过程的直接观察。该项目将利用北美边缘社区地震实验的现有数据来表征北卡罗来纳州近海的断层沉积。将建立一个具有新颖触发机制的按比例的物理模型，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，以结合初始条件、启动机制和故障行为如何联系在一起。作为更广泛影响的一部分，作为该项目的一部分，一名研究生将接受多学科(地震学、沉积学、地质力学和工程学)的培训。总体而言，该项目将通过改进对美国海岸线边坡坍塌和海啸产生的风险评估，为社会做出贡献。该项目将把GeoPRISMS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，从而能够对斜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)以及震源(位置和能量)的控制，同时启动斜坡破坏并观察破坏动力学。数值模型将模拟在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测联系起来的手段。该项目将解决以下假设：1)海底斜坡崩塌沉积物和邻近的未崩塌沉积物中地震速度剖面的差异记录了不同的有效应力和强度剖面；2)崩塌开始时沉积物的有效应力和强度影响斜坡崩塌类型和失稳海底沉积物的活化行为；3)斜坡崩塌触发机制影响斜坡崩塌动力学和演化，从而影响其引发海啸的潜力。该项目的总体目标是描述和描述破坏类型、沉积、初始条件和驱动机制之间的联系，这将增加利用沉积记录中的斜坡破坏沉积来评估驱动机制的能力。这将提高我们了解斜坡破坏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进行限制，这可以为斜坡坍塌和相关海啸危险的风险评估提供信息。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。

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.