3D relationship between substrate fluid flow and submarine slope failure within the western Santa Barbara Channel

Offshore 3D seismic-reflection data and high-resolution 2D profiles are used to investigate the role of substrate fluid migration in submarine slope failure along the northwestern Santa Barbara Channel, California. Neural-network seismic attribute workflows are utilized to calculate and map probable fluid migration pathways within the 3D seismic data that extend from the shallow substrate to over 3 km below the seafloor. These results are then projected onto 3D mapped fault planes and horizons, providing insight into the relationship between structure, stratigraphy, and substrate fluid flow. In addition, high-resolution 2D sparker seismic profiles compliment the lower-resolution 3D data, providing higher resolution data in the shallow substrate. Results from the study indicate fluid migration is primarily focused within regions of anticlinal folding and along discrete faults. Fluid migration pathways commonly root into the up-dip limit of reverse polarity bright spots. Similarly, fluid pathways often terminate up section into shallow bright spots. These observations help delineate a complex network of fluid leakage and trapping that is closely tied to faulting and deformation patterns. In the shallow substrate, fluid pathways are focused within zones of deformation located below the Gaviota landslide and a seafloor fissure on its west flank. Additional fluid migration pathways are clustered below seafloor pockmarks and below the upper slope portion of the Conception Fan, a region that also exhibits significant frequency attenuation due to gas charging. Growth folding and the stratal geometry of basin-floor depocenters (e.g., onlap and pinch-out sequences) are primary controls on sub-surface fluid migration, trapping, and the development of pore-fluid overpressure. These results suggest that substrate fluids play a critical role in slope failure processes within the western Santa Barbara Channel.