Geoacoustic Models: Washington State Continental Margin
Abstract
Knowledge of the Washington continental margin geology is critical in predicting acoustic response, since the region is a shallow-water, bottom- interacting area. The sediments are primarily terrigenous with less than 3% calcareous constituents on the shelf and slope and less than 10% calcareous constituents in the basin areas of the region. On the Washington continental shelf, sediments form bands of sands, silty sands, and muds that roughly parallel the coastline as a result of prevailing current patterns. North of the Strait of Juan de Fuca, sediment grain-size patterns are highly irregular and include significant gravel deposits. The entire continental shelf is covered with only 150 meters and less of unconsolidated sediment. Sediment cover on the slope is more variable and ranges between a few meters on the tops of ridges to as much as 1600 meters in the valleys. The Cascadia Basin contains the thickest sediment (2500 meters) opposite the Columbia River and thins toward the Juan de Fuca Ridge. Acoustic basement is a siltstone beneath the shelf, a mudstone beneath much of the slope, and oceanic basalt beneath the deep-sea fans and basins. Seven geoacoustic provinces have been defined and mapped on the basis of sediment type and grain size. Each geoacoustic province has an accompanying geoacoustic model suitable for input to acoustic field models in which sediment physical properties are modeled as a function of depth.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1985
- Accession Number
- ADA153781
Entities
People
- Dawn Lavoie
Organizations
- United States Naval Research Laboratory