EXPLORING SHALLOW SUBSURFACE FLUID FLOW AND GEOHAZARDS IN MARINE SEDIMENTS THROUGH CORING, LOGGING, EXPERIMENTS, AND MODELS

Oceanic sediments and crust are active hydrologic systems that influence geohazards, heat transport, nutrient fluxes, and many other processes yet we have limited information about the magnitudes and variability of these systems. Scientific ocean drilling provides unprecedented access to shallow marine sediments to improve our understanding of this subseafloor flow system including quantification of fluid flow properties and dynamics, sediment deformation, and sediment strength. I will summarize how our ability to determine in situ pressures and permeability have evolved during through scientific ocean drilling with advancements in downhole measurements, better access to samples, dedicated samples for onshore geomechanical studies, and multidisciplinary collaborations offshore and onshore. These advancements provide a clearer understanding on the magnitude of shallow overpressure, the importance of overpressure for submarine landslide initiation and dynamics, and the hydrologic and strength states of inputs to active and passive margins. I will demonstrate how these in situ and laboratory-based characterizations have led to improved process-based models on fluid flow focusing and slope failure along passive margins, timing and thickness of submarine landslides, and freshwater in oceanic sediments. Our advances in measurements, analyses, and models will be showcased by examples and data from multiple expeditions of the Ocean Drilling Program, the Integrated Ocean Drilling Program, and the International Ocean Discovery Program.