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Geotechnical Properties of Quaternary Marine Sediments of the Eel River Plateau, Southern Cascadia Margin

Description: 

Submarine landslides are frequently triggered by earthquakes but there can be a variety of factors that trigger or precondition a slope to failure including weak layers in the sediment, storm waves, and sediment unroofing. Although earthquakes can trigger submarine landslides, active margins have fewer submarine landslides than passive margins despite having higher levels of seismicity. This observation supports the concept of seismic strengthening which suggests that sediment exposed to repeated earthquake shaking dewaters and densifies causing enhanced strength. We focus on the southern end of the Cascadia Subduction Zone, where the highest historical seismicity rate along the Cascadia margin has occurred due to the northward migration of the Mendocino Triple Junction, resulting in a broad regional uplift. Moreover, there is a high volume of terrestrial sediment input in this area from the Eel River and other fluvial systems that feed into the southern end of the Cascadia Subduction Zone. Despite the high levels of seismicity and the high volume of sediment accumulation, recent studies document a distinct lack of slope failure on the upper slope. Given this observation, we aim to understand the physical properties that contribute to the slope stability in this region, including whether there is enhanced strength or other mechanical differences that might play a role in enhanced slope stability. We measure undrained shear strength using a fall cone device, grain size, and Atterberg limits and integrate them with CT scans, photographs, physical property logs, and radiocarbon dates. Using this collected data we will be able to provide a new insight into the slope stability of the region that will further the understanding of the possible implications for regional geohazards and how they can affect offshore infrastructure.

Session: From Faults to Fjords: Earthquake Evidence in Terrestrial and Subaqueous Environments [Poster Session]

Type: Poster

Date: 5/1/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Bailey

Student Presenter: Yes

Invited Presentation: 

Authors