MICROFOSSILS AS DRIVERS FOR SUBMARINE LANDSLIDES?
This project was recently funded by the National Science Foundation as a NSF CAREER grant.
Underwater landslides are serious natural hazards with large societal and socioeconomic consequences. They occur globally, can cause tsunamis, and pose significant threats to human life and infrastructure, especially near coasts. To reduce this impact on people and infrastructure, it is critical to advance our understanding of slope stability in ocean sediments. This project focuses on continental margins, where earthquakes typically do not occur, and as such, do not act as triggers for landslides. In these sites, it remains unclear how the skeletal remains of microorganisms that live in the ocean and end up in ocean sediments could potentially weaken and precondition those sediments for failure and underwater landslides.
This research project integrates experimental and numerical efforts and aims to characterize the role of microfossils in generating weak layers, which could become large-scale glide planes for submarine landslides. In this project, marine sediments will be systematically mixed with diatomite in varying concentrations and under repeatable conditions. The research goals are to determine key microfossil concentrations with threshold behavior, exact location within the sediment package, and burial conditions under which overpressure may be induced and wide-spread failure initiated within or above a microfossil-rich weak layer. Therefore, this proposed research will not only provide insights into slope failure mechanisms for microfossil-rich sediments but will also help in identifying potential future glide planes from cores and/or logging data from submarine and lacustrine settings where landslides may occur without external triggers like earthquakes. To document mechanical, hydraulic, and shear properties of microfossil-rich marine sediments, uniaxial resedimentation and constant rate of strain consolidation, as well as direct shear and triaxial shear experiments, will be conducted at effective stresses corresponding to common landslide initiation depths. Microstructural changes, microfossil deformation, and development of shear failure planes will be qualitatively and quantitatively characterized by integrating analysis of hydromechanical data from deformation experiments with microscale imaging observations. Numerical slope stability models will provide insights into upscaling measured properties and introducing heterogeneous layered systems that analyze the interaction between microfossil-rich weak layers with over-and underlying non-biogenic sediments.