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可能对沿海地区产生重大影响。在人口稠密的美国大西洋中部近海大陆边缘，约15%的大陆坡度显示出大型海底山体滑坡留下的伤痕。本研究旨在了解这些共同特征背后的驱动机制。通过对现有数据应用新的分析技术，将研究沉积物中的流体在引发山体滑坡中所起的作用。边坡的破坏可以是渐进的，也可以是灾难性的，破坏的类型将控制对沿海地区的影响的严重程度。这项研究的结果将使我们更好地了解以下问题：(1)灾难性斜坡崩塌引起的海啸的自然灾害风险；(2)逐渐崩塌和灾难性崩塌释放被困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。该项目支持培训两名研究生和一名博士后研究员。将使用开放获取的地震反射数据检查北卡罗来纳州近海的恐惧角和库里塔克海底山体滑坡。这些和其他斜坡破坏的一个关键问题是“升高的孔隙流体压力在促进斜坡失稳方面的作用是什么？”利用叠前波形反演和高质量的地震资料，将获得这两个滑坡复合体内外沉积物的P波和S波速度变化的详细信息。新的速度信息将与取心和钻井中有关沉积物特性的其他可用信息相结合，以限制故障区域和未故障区域之间沉积物物理特性的变化。孔隙流体压力的变化将使用一种将速度和有效应力联系起来的有效介质方法来估计。此外，地震剖面将通过使用PWI获得的速度进行叠前深度偏移来重新处理，以改善对滑动特征的成像。这项研究将在关于这些滑块的越来越多的信息中增加关于原位沉积物性质和库里塔克滑坡体内部和周围的应力状态的关键新约束。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。

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.