Collaborative Research: Constraints on sediment physical properties at the Cape Fear and Currituck landslides from velocity analysis of new, open access seismic reflection data

发生在大陆近海的海底滑坡会对沿海地区产生重大影响。在人口稠密的美国大西洋中部沿海的大陆边缘，大约15%的大陆斜坡上有大型海底滑坡留下的疤痕。本研究旨在了解这些共同特征背后的驱动机制。沉积物中的流体在引发滑坡中所起的作用将通过对现有数据应用新的分析技术来检验。边坡破坏可以是渐进性的，也可以是突发性的，破坏的类型决定了对沿海地区影响的严重程度。本研究的结果将有助于我们更好地理解以下问题：(1)灾难性坡损引发的海啸带来的自然灾害风险；(2)逐渐和灾难性坡损释放温室气体时的潜在影响；(3)更广泛科学意义上的大陆边缘沉积体系。本项目支持培养2名研究生和1名博士后。北卡罗莱纳州近海的Cape Fear和Currituck海底滑坡将使用开放的地震反射数据进行检查。这些和其他边坡破坏的一个关键问题是“孔隙流体压力升高在促进边坡失稳中的作用是什么？”利用叠前波形反演（PWI）和高质量的地震资料，将获得这两个滑坡体内外沉积物的P波和S波速度变化的详细信息。新的速度信息将与来自取心和钻井的沉积物性质的其他可用信息相结合，以限制失效区域和非失效区域之间沉积物物理性质的变化。孔隙流体压力的变化将使用与速度和有效应力相关的有效介质方法来估计。此外，利用PWI获得的速度，通过叠前深度偏移对地震剖面进行再处理，以改善滑动特征的成像。这项研究将为这些滑坡的不断增长的信息体增加对原位沉积物特性和Cape Fear和Currituck滑坡复合体内部和周围的应力状态的关键新限制。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。

Seafloor landslides that occur just offshore of continents can have significant impacts on coastal areas. On the continental margin offshore of the heavily populated U.S. Mid-Atlantic, about 15% of the continental slope shows scars from large submarine landslides. This study aims to understand the driving mechanisms behind these common features. The role that fluids within the sediments play in triggering landslides will be examined by applying new analysis techniques to existing data. Slope failure can occur gradually or catastrophically, and the type of failure will control the severity of the impacts to coastal areas. Results of this study will provide a better understanding of the following: (1) the natural hazard risk from tsunamis generated by catastrophic slope failures, (2) potential impacts when trapped greenhouse gases are released from both gradual and catastrophic failures, and (3) sedimentary systems along continental margins in a broader scientific sense. The project supports the training of two graduate students and a post-doctoral investigator.The Cape Fear and Currituck submarine landslides offshore North Carolina will be examined using open-access seismic reflection data. A key question for these and other slope failures is "What is the role of elevated pore-fluid pressure in promoting slope instability?" Using pre-stack waveform inversion (PWI) and high-quality seismic data, detailed information on variations in P- and S- wave velocity of sediments inside and outside of these two slide complexes will be obtained. The new velocity information will be integrated with other available information on sediment properties from coring and drilling to constrain variations in sediment physical properties between failed and un-failed regions. Variations in pore-fluid pressure will be estimated using an effective-medium approach relating velocity and effective stress. Also, the seismic profiles will be reprocessed through pre-stack depth migration using velocities obtained by PWI to improve imaging of slide features. This study will add critical new constraints on in situ sediment properties and the stress state within and around the Cape Fear and Currituck slide complexes to the growing body of information on these slides.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.