New Seafloor Bathymetry and Backscatter Mapping of the Southern California Borderland

TitleNew Seafloor Bathymetry and Backscatter Mapping of the Southern California Borderland
Publication TypeConference Abstract
AuthorsConrad, JE, Dartnell, P, Raineault, NA, Brothers, DS, Roland, EC, Kane, R, Gee, L, Walton, MAL, Heffron, E, Saunders, M
Conference Name2018 Fall Meeting, American Geophysical Union (AGU)
Conference LocationWashington, DC
Conference DatesDecember 10-14
Keywordsbackscatter, bathymetry, California, e/v nautilus, mapping, multibeam, Ocean Exploration Trust

High-resolution (25 m or better) multibeam echosounder data is crucial for understanding seafloor geology and habitats, especially as they relate to offshore earthquake and landslide hazard assessment, sediment dispersal patterns, and resource management. Prior to 2011, however, less than about 20% of the southern California seafloor within 100 km of the coast had been mapped using multibeam techniques, with high-resolution mapping mostly limited to within about 40 km of the major urban centers of Los Angeles, San Diego, and Santa Barbara. Some parts of the coast were lacking high-resolution maps of the seafloor beyond only 10 km offshore.

Within the last several years, however, data from new high-resolution seafloor surveys have become available, including those by the U.S. Geological Survey/University of Washington (2016), the Ocean Exploration Trust (2015-2018), Scripps Institution of Oceanography (2013, 2017), and the National Oceanic and Atmospheric Administration (2011, 2016-2017) covering more than 15,000 km2 and extending high-resolution mapping out to about 100 km offshore between San Diego and Ventura, Calif. These new data provide a wealth of new information, and have facilitated the generation of a series of new higher-resolution bathymetry and backscatter maps of the Continental Borderland of southern California. These new data allow a reevaluation of active deformation and faulting for use in earthquake hazard assessment, and have led to the recognition of numerous previously unknown submarine landslides, including the largest yet discovered (covering ~200 km2) in the California Continental Borderland. Water column backscatter data has revealed at least 20 newly recognized seafloor seeps, providing new information regarding subseafloor fluid flow and seafloor habitats. The new data also provide valuable new insights regarding sediment pathways and transport in the offshore basins.