This part of USGS Data Series 781 (Golden, 2019) presents 2-m-resolution acoustic backscatter data for the Offshore of Point Buchon, California, map area. Backscatter data were collected by Fugro Pelagos in 2008 using a combination of 400-kHz Reson 7125, 240-kHz Reson 8101, and 100-kHz Reson 8111 multibeam echosounder systems. The data were post-processed by the California State University Monterey Bay Seafloor Mapping Lab and the University of California Santa Cruz Center for Integrated Spatial Research. The acoustic backscatter data are available as a georeferenced TIFF image. Within the final imagery, brighter tones indicate higher backscatter intensity, and darker tones indicate lower backscatter intensity. The intensity represents a complex interaction between the acoustic pulse and the seafloor, as well as characteristics within the shallow subsurface, providing a general indication of seafloor texture and composition. Backscatter intensity depends on the acoustic source level; the frequency used to image the seafloor; the grazing angle; the composition and character of the seafloor, including grain size, water content, bulk density, and seafloor roughness; and some biological cover. Harder and rougher bottom types such as rocky outcrops or coarse sediment typically return stronger intensities (high backscatter, lighter tones), whereas softer bottom types such as fine sediment return weaker intensities (low backscatter, darker tones).

In November 2021, the U.S. Geological Survey collected high-resolution multibeam sonar data in the vicinity of Eel Pond, in Woods Hole, Massachusetts using a dual-head Teledyne Seabat T20-R multibeam echo sounder (MBES). The main objective of this survey was to evaluate new sonar system features prior to their use in future field activities. In addition to bathymetry and relative acoustic backscatter data, normalized acoustic backscatter data were also collected. Unlike relative backscatter data, normalized backscatter data compensate for adjustments made to sonar power, gain, absorption, spreading, and frequency parameters made during acquisition. In order for backscatter intensity levels to remain consistent along survey lines, and from line to line, relative backscatter data require that minimal adjustments are made to these parameters during acquisition, which can degrade the sonar performance for a given survey site. However, the ability to allow the sonar acquisition software to change sonar parameters based on variations in bathymetry and the survey environment during acquisition allows these parameters to be optimized. Having these parameters optimized for this survey allowed the USGS to evaluate this new normalized backscatter capability to ensure the collected backscatter intensity levels were referenced to a factory calibrated level. Eel Pond in Woods Hole, MA was chosen as a test area for its proximity to the USGS Coastal and Marine Science Center. It provides a variety of substrates on which to evaluate the performance of the sonar, and bathymetric/backscatter data of this area may prove useful to other projects and institutions in the area.

The U.S. Geological Survey (USGS) Woods Hole Coastal and Marine Science Center (WHCMSC) completed a bathymetric and shallow seismic-reflection survey during the period of June 9, 2021 to June 24, 2021 in water depths from 2 m to 30 m for a portion of the outer Cape Cod nearshore environment between Marconi and Nauset Beaches. The products from this survey will help to support white shark research on their shallow-water behavior in the dynamic nearshore environment at Cape Cod National Seashore (CACO). CACO visitors’ safety is threatened by interactions between the public and white sharks. This project provides CACO with baseline data and information on nearshore white shark habitat, specifically in the nearshore shoreface, bathymetric trough, and longshore bar. This data release provides the geophysical data collected from outer Cape Cod during USGS Field Activities 2021-002-FA in 2021.

This 2-m-resolution acoustic backscatter data for the Offshore of Arcata, California, map area is part of USGS Data Series 781 (Golden and Cochrane, 2019). Backscatter data were collected by Fugro Pelagos in 2007 using a combination of 400-kHz Reson 7125, 240-kHz Reson 8101, and 100-kHz Reson 8111 multibeam echosounder systems. The data were post-processed by the California State University Monterey Bay Seafloor Mapping. The acoustic backscatter data are available as a georeferenced TIFF image. Within the final imagery, brighter tones indicate higher backscatter intensity, and darker tones indicate lower backscatter intensity. The intensity represents a complex interaction between the acoustic pulse and the seafloor, as well as characteristics within the shallow subsurface, providing a general indication of seafloor texture and composition. Backscatter intensity depends on the acoustic source level; the frequency used to image the seafloor; the grazing angle; the composition and character of the seafloor, including grain size, water content, bulk density, and seafloor roughness; and some biological cover. Harder and rougher bottom types such as rocky outcrops or coarse sediment typically return stronger intensities (high backscatter, lighter tones), whereas softer bottom types such as fine sediment return weaker intensities (low backscatter, darker tones).

This 2-m-resolution acoustic backscatter data for the Offshore of Cape Mendocino, California, map area is part of USGS Data Series 781 (Golden, 2019). Backscatter data were collected by Fugro Pelagos in 2008 using a combination of 400-kHz Reson 7125, 240-kHz Reson 8101, and 100-kHz Reson 8111 multibeam echosounder systems. The data were post-processed by the California State University Monterey Bay Seafloor Mapping Lab. The acoustic backscatter data are available as a georeferenced TIFF image. Within the final imagery, brighter tones indicate higher backscatter intensity, and darker tones indicate lower backscatter intensity. The intensity represents a complex interaction between the acoustic pulse and the seafloor, as well as characteristics within the shallow subsurface, providing a general indication of seafloor texture and composition. Backscatter intensity depends on the acoustic source level; the frequency used to image the seafloor; the grazing angle; the composition and character of the seafloor, including grain size, water content, bulk density, and seafloor roughness; and some biological cover. Harder and rougher bottom types such as rocky outcrops or coarse sediment typically return stronger intensities (high backscatter, lighter tones), whereas softer bottom types such as fine sediment return weaker intensities (low backscatter, darker tones).

These metadata describe acoustic-backscatter collected during a 2015 multibeam echosounder survey near Cross Sound, southeast Alaska. Data were collected by the U.S. Geological Survey (USGS) and the Alaska Department of Fish and Game (ADFG) aboard the ADFG R/V Solstice during USGS field activity 2015-629-FA. The acoustic-backscatter data are provided as a GeoTIFF.

This part of the data release includes 10-m resolution multibeam acoustic-backscatter data collected in 2016 in Catalina Basin, southern California. The data are presented as a TIFF file. In February 2016 the University of Washington in cooperation with the U.S. Geological Survey, Pacific Coastal and Marine Science Center (USGS, PCMSC) collected multibeam bathymetry and acoustic backscatter data in Catalina Basin aboard the University of Washington's Research Vessel Thomas G. Thompson. Data were collected using a Kongsberg EM300 multibeam echosounder hull-mounted to the 274-foot R/V Thomas G. Thompson. The USGS, PCMSC processed these data and produced a series of bathymetric surfaces and acoustic-backscatter images for scientific research purposes.

High resolution bathymetric, sea-floor backscatter, and seismic-reflection data were collected offshore of southeastern Louisiana aboard the research vessel Point Sur on May 19-26, 2017, in an effort to characterize mudflow hazards on the Mississippi River Delta front. As the initial field program of a research cooperative between the U.S. Geological Survey, the Bureau of Ocean Energy Management, and other Federal and academic partners, the primary objective of this cruise was to assess the suitability of sea-floor mapping and shallow subsurface imaging tools in the challenging environmental conditions found across delta fronts (for example, variably distributed water column stratification and widespread biogenic gas in the shallow subsurface). Approximately 675 kilometers (km) of multibeam bathymetry and backscatter data, 420 km of towed chirp data, and 550 km of multichannel seismic data were collected. Varied mudflow (gully, lobe), prodelta morphologies, and structural features were imaged in selected survey areas from Pass a Loutre to Southwest Pass.

High resolution bathymetric, sea-floor backscatter, and seismic-reflection data were collected offshore of southeastern Louisiana aboard the research vessel Point Sur on May 19-26, 2017, in an effort to characterize mudflow hazards on the Mississippi River Delta front. As the initial field program of a research cooperative between the U.S. Geological Survey, the Bureau of Ocean Energy Management, and other Federal and academic partners, the primary objective of this cruise was to assess the suitability of sea-floor mapping and shallow subsurface imaging tools in the challenging environmental conditions found across delta fronts (for example, variably distributed water column stratification and widespread biogenic gas in the shallow subsurface). Approximately 675 kilometers (km) of multibeam bathymetry and backscatter data, 420 km of towed chirp data, and 550 km of multichannel seismic data were collected. Varied mudflow (gully, lobe), prodelta morphologies, and structural features were imaged in selected survey areas from Pass a Loutre to Southwest Pass.

In summer 2018, the U.S. Geological Survey partnered with the U.S Department of Energy and the Bureau of Ocean Energy Management to conduct the Mid-Atlantic Resources Imaging Experiment (MATRIX) as part of the U.S. Geological Survey Gas Hydrates Project. The field program objectives were to acquire high-resolution 2-dimensional multichannel seismic-reflection and split-beam echo sounder data along the U.S Atlantic margin between North Carolina and New Jersey to determine the distribution of methane gas hydrates in below-sea floor sediments and investigate potential connections between gas hydrate dynamics and sea floor methane seepage. MATRIX field work was carried out between August 8 and August 28, 2018 on the research vessel Hugh R. Sharp and resulted in acquisition of more than 2,000 track-line kilometers of multichannel seismic-reflection and co-located split-beam echo sounder data, along with wide-angle seismic reflection and refraction data from 63 expendable sonobuoy deployments.