usSEABED: A USGS Pacific Coast Offshore Surficial Sediment Data and Mapping Project
- Jane Reid
United States Geological Survey (USGS)
Over the past 50 years there has been an explosion in scientific interest, research effort and information gathered on the geologic character of the U.S. continental margin. Data and information from thousands of publications has greatly increased our scientific understanding of the character of the shelf surface, but rarely have those data been combined and integrated.
The USGS and partners, as part of a national seabed characteristics database, usSEABED, published the first release of Pacific Coast point data in June 2006. This report contains the compilation of published and unpublished sediment texture and other geologic and biologic data about the seafloor from diverse sources. usSEABED is an innovative system developed to utilize both lab-based analyses and numeric data from descriptive data – such as core logs or photographs, derived from the application of fuzzy set theory on geologic language – together in a unified database. Examples displaying distribution of data attributes, such as grain size, constituent components, and sediment color, are included. This database contains information that is useful to the marine science community for studies of the Pacific Coast continental margin.
Due to the esoteric nature of the database, users are strongly encouraged to read the supporting documentation within the publication to ensure that data are used appropriately.
Announcements and other publications from the national usSEABED database are available through the usSEABED website (http://walrus.wr.usgs.gov/usseabed/). Data can be seen on the USGS ArcIMS server (http://coastalmap.marine.usgs.gov/regional/contusa/westcoast/index.html
Version 1.0 of the Pacific Coast usSEABED publication can be directly accessed at http://pubs.usgs.gov/ds/2006/182.
Summary to DateThe usSEABED Pacific Coast data release provides an integrated database of seabed characteristics for the Pacific continental margin of the United States that fills a need for information about seabed characteristics for use by geologists, ecologists, biologists, resource managers, and national defense investigators. usSEABED provides a digital, integrated database of existing physical data and information from the seafloor, including textural, statistical, geochemical, geophysical, and compositional information. It uses the dbSEABED data mining and processing software to extend the coverage of information in areas where data coverage is more descriptive than quantitative (Figure 1). Included in the publication are direct links to source metadata files that provide known facts about the type of data, analytical techniques, and other pertinent information; in this way, usSEABED provides critical knowledge about scientific investigations of the Pacific coast.
The Pacific Coast coverage of point data extends from Cape Flattery (including Puget Sound) to the Mexican border, including major estuaries such as San Francisco and Monterey Bays, beaches, and extends seaward across the continental shelf and slope. More than 100 different data sources containing over 65,000 data points from more than 25,000 sites are currently contained in usSEABED for the Pacific.
The national usSEABED database is a very large compilation, containing complex assortments of data on the geology of the seafloor. Although this database was developed for use in conducting studies of offshore sedimentary character for assessing and characterizing benthic habitats and marine aggregates, it has many more potential applications by the marine science community and other users. Users are encouraged to generate their own queries and extract information to meet specific needs. Other potential applications where data and maps from usSEABED might be useful are:
* Research ocean observatories and monitoring
* Coastal zone/ocean management and planning
* Homeland security, military applications
* Seafloor engineering planning and design
* Ocean disposal site placement, monitoring
* Cultural resources
* Fisheries management, marine protected areas
* Seabed roughness, bedform distribution, critical shear stress, sediment transport flux
* Public education
* Seafloor bottom friction values for calibration of modeling processes, such as the effects of storm waves on sediment mobility and transport
It is expected that usSEABED will continue to expand both by the incorporation of new data sets and by the utilization and mining of the data in new and different ways. As significant changes are made, we expect to reissue usSEABED as updated publications. Data contributions and/or additional partners are welcomed. For information, please contact the Principal Investigator, Jane Reid, at email@example.com.
Version 1.0 of the Pacific Coast usSEABED publication can be directly accessed at is at http://pubs.usgs.gov/ds/2006/182.
- Substrate characterization
- Geological characterization
- Habitat association
Study MethodsMore than 100 different data sources containing over 65,000 data points from more than 25,000 sites are currently contained in usSEABED for the Pacific. At the core of usSEABED is dbSEABED, a data-mining program based on the application of fuzzy set theory to marine geological and biological data. Fuzzy set theory allows expansion of coverage of the seafloor by the use of word-based data from core logs, sample descriptions, photos, and videos, as well as the more standard numeric data from a laboratory.
The dbSEABED program, in part, parses word-based descriptive data such as "brown fine sand with abundant shells; seagrass and some pebbles; whiff of h2s" into numeric, georeferenced data. This process extends the data coverage of the seabed by using words, an important data type characterizing the seabed. While a simplified explanation of the parsing process is provided, more information can be found within the usSEABED publications or on the dbSEABED website (http://instaar.colorado.edu/~jenkinsc/dbseabed/).
The dbSEABED program applies fuzzy set theory concepts to geological descriptions, using:
1) a parser that divides the descriptions into arithmetic equations;
2) a thesaurus that attaches meanings and memberships to the quantifiers, modifiers, and objects; and
3) a linear weighted assembly of the numerical totals.
In the dbSEABED program, word memberships can be defined across many parameters—not just grain size. The outputs are numeric values, representing fuzzy memberships of parameters such as mud, grain sizes, carbonate, organic carbon, grain types, sedimentary features, rock, weed coverages, and engineering strengths.
Users of the usSEABED dataset based on descriptive data should be aware of the nature of the data; that is, fuzzy memberships that are best thought of as a measure of truth or possibility, neither probability nor the results of rigorous analytical methods.
Ongoing statistical comparisons are made between the lab-based and word-based data outputs for calibration of the parsing process, with a goal of no more than one phi size between the parsed and lab-based outputs from the same sample. Larger differences in some samples may be due to an inherent difference in the sample analyzed: for instance, the parsed output may be on the whole sample including stones, shells, or other large objects, and the lab-based data may be from the analysis of the matrix only. Each user may choose which output type (or both) fit the needs of a given study.
Figures and Images
Figure 1: Examples of word-based components and features mined from a variety of scientific studies and reports to augment the usSEABED database.