Backscatter A (8101): Offshore of San Francisco, California, 2004

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Abstract/Contents

Abstract
This layer is a georeferenced raster image containing acoustic-backscatter data for the offshore area of San Francisco, California. The acoustic-backscatter map of the area was generated from backscatter data collected by Fugro Pelagos and by California State University, Monterey Bay (CSUMB). Mapping was completed between 2004 and 2008, using a combination of 400-kHz Reson 7125 and 244-kHz Reson 8101 multibeam echosounders. 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). A map that shows these data is published in Open-File Report 2015-1068, "California State Waters Map Series--Offshore of San Francisco, California." This layer is part of USGS Data Series 781.
Purpose
In 2007, the California Ocean Protection Council initiated the California Seafloor Mapping Program (CSMP) to create a comprehensive seafloor map of high-resolution bathymetry, marine benthic habitats and geology within the 3-nautical-mile limit of California's State Waters. CSMP has divided coastal California into 110 map blocks, each to be published individually as United States Geological Survey Open-File Reports (OFRs) or Scientific Investigations Maps (SIMs) at a scale of 1:24,000. Maps display seafloor morphology and character, identify potential marine benthic habitats and illustrate both the seafloor geology and shallow (to about 100 m) subsurface geology. Data layers for bathymetry, bathymetric contours, acoustic backscatter, seafloor character, potential benthic habitat and offshore geology were created for each map block, as well as regional-scale data layers for sediment thickness, depth to transition, transgressive contours, isopachs, predicted distributions of benthic macro-invertebrates and visual observations of benthic habitat from video cruises over the entire state. This coverage can be used to to aid in assessments and mitigation of geologic hazards in the coastal region and to provide sufficient geologic information for land-use and land-management decisions both onshore and offshore. These data are intended for science researchers, students, policy makers, and the general public. This information is not intended for navigational purposes.The data can be used with geographic information systems (GIS) software to display geologic and oceanographic information.

Description

Type of resource cartographic, software, multimedia
Form Raster Dataset
Place Santa Cruz, California, US
Publisher Geological Survey (U.S.)
Date valid 2004
Publication date 2014
Edition 1.0
Language English
Digital origin born digital
Map data Scale not given. ; Custom projection W 122°37ʹ4ʺ--W 122°24ʹ57ʺ/N 37°51ʹ26ʺ--N 37°41ʹ49ʺW 122°37ʹ4ʺ--W 122°24ʹ56ʺ/N 37°51ʹ26ʺ--N 37°41ʹ49ʺ, Scale not given ; EPSG::4326

Creators/Contributors

Creator Erdey, Mercedes D.
Creator Bretz, Carrie K.
Creator Dartnell, Peter
Creator Kvitek, Rikk G.
Creator Seafloor Mapping Lab
Creator Pacific Coastal and Marine Science Center
Creator Golden, Nadine E.

Subjects

Subject Coasts
Subject Submarine topography
Subject Submarine geology
Subject Ocean bottom
Subject Seismic reflection method
Subject California
Subject San Mateo County (Calif.)
Subject San Francisco (Calif.)
Subject Marin County (Calif.)
Subject Pacific Ocean
Subject San Francisco Bay (Calif.)
Subject 2004
Subject Imagery and Base Maps
Subject Oceans
Subject Environment
Subject Geoscientific Information
Genre Geospatial data
Genre Cartographic dataset

Bibliographic information

WGS84 Cartographics This layer is presented in the WGS84 coordinate system for web display purposes. Downloadable data are provided in native coordinate system or projection.
Location https://purl.stanford.edu/kn551fj5393

Access conditions

Use and reproduction
This item is in the public domain. There are no restrictions on use.
Copyright
This work is in the Public Domain, meaning that it is not subject to copyright.

Preferred citation

Dartnell, P., Erdey, M.D., Kvitek, R.G., and Bretz, C.K. (2014). Backscatter A (8101): Offshore of San Francisco, California, 2004. California State Waters Map Series Data Catalog: U.S. Geological Survey Data Series 781. Available at: http://purl.stanford.edu/kn551fj5393.

Collection

California State Waters Map Series Data Catalog

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