Marine Neotectonic Investigations Using Integrated AUV and ROV Surveys

Wednesday, 17 December 2014: 9:00 AM
Charles K Paull1, David W Caress1, Roberto Gwiazda2, Eve M Lundsten2, Krystle Anderson1, Esther J Sumner1, Mary McGann3, Daniel S Brothers4 and Juan Carlos Herguera5, (1)Monterey Bay Aquarium Research Institute, Moss Landing, CA, United States, (2)Monterey Bay Aquarium Research Institute, Watsonville, CA, United States, (3)USGS California Water Science Center Menlo Park, Menlo Park, CA, United States, (4)Pacific Coastal and Marine Science Center Santa Cruz, Santa Cruz, CA, United States, (5)CICESE, San Diego, CA, United States
Detailed investigations of 15 sites associated with seafloor faults and/or slope failures have been conducted with MBARI’s Autonomous Underwater Vehicles (AUVs) and Remotely Operated Vehicles (ROVs). The motivation for these surveys is to better constrain neotectonic deformation of the seafloor and thus to evaluate potential seafloor geohazards. The coupled use of AUVs and ROVs has enabled marine neotectonic investigations to be achieved at similar observational detail to that previously only possible on land. The AUV surveys provide 1-m resolution bathymetric grids with vertical resolutions of ~10 cm along with chirp sub-bottom profiles that allow subtle deformation on and near the seafloor to be detected. ROV surveys enable precisely located push core and vibracore samples. Sampling strategies include taking transects of closely spaced cores across faults (comparable to trenching on land), and taking transects of horizontal push cores along the faces of scarps where reflectors in chirp profiles crop out or occur in the shallow subsurface. The timing of fault movement can then be established via radiocarbon dating of appropriate material within the sediment samples. The marine environment offers some inherent advantages for neotectonic investigations over the terrestrial environment, as the seafloor geomorphology is relatively unaffected by the deleterious effects of human development (agriculture and urbanization), has no vegetative cover, and is likely to experience continuous deposition of 14C datable materials. Examples will be shown of how AUV and ROV technologies help to constrain the extent, style, and timing of deformation associated with: the San Gregorio fault, offshore central California; the Palos Verdes and San Diego trough faults off southern California; transform faults within the Gulf of California; and young slump scars off Monterey, California. The increased resolution provided by these tools frequently leads to interpretations that differ from what could be inferred from surface-ship collected bathymetric surveys and ship-based coring.