Skip to main content
U.S. flag

An official website of the United States government

Stability of submerged slopes on the flanks of the Hawaiian Islands, a simplified approach

January 1, 1994

Undersea transmission lines and shoreline AC-DC conversion stations and near-shore transmission lines are being considered as part of a system for transporting energy between the Hawaiian Islands. These facilities will need to be designed so that they will not be damaged or destroyed by coastal or undersea landslides. Advanced site surveys and engineering design of these facilities will require detailed site specific analyses, including sediment sampling and laboratory testing of samples, in situ testing of sediment and rock, detailed charting of bathymetry, and two- or three-dimensional numerical analyses of the factors of safety of the slopes against failure from the various possible loading mechanisms. An intermediate approximate approach can be followed that involves gravity and piston cores, laboratory testing and the application of simplified models to determine a seismic angle of repose for actual sediment in the vicinity of the planned facility. An even simpler and more approximate approach involves predictions of angles of repose using classification of the sediment along a proposed route as either a coarse volcaniclastic sand, a calcareous ooze, or a muddy terrigenous sediment. The steepest slope that such a sediment can maintain is the static angle of repose. Sediment may be found on slopes as steep as these, but it must be considered metastable and liable to fail in the event of any disturbance, storm or earthquake. The seismic angle of repose likely governs most slopes on the Hawaiian Ridge. This declivity corresponds to the response of the slope to a continuing seismic environment. As a long history of earthquakes affects the slopes, they gradually flatten to this level. Slopes that exceed or roughly equal this value can be considered at risk to fail during future earthquakes. Seismic and static angles of repose for three sediment types are tabulated in this report.

Publication Year 1994
Title Stability of submerged slopes on the flanks of the Hawaiian Islands, a simplified approach
DOI 10.3133/ofr94638
Authors Homa J. Lee, Michael Torresan, William McArthur
Publication Type Report
Publication Subtype USGS Numbered Series
Series Title Open-File Report
Series Number 94-638
Index ID ofr94638
Record Source USGS Publications Warehouse
USGS Organization Volcano Hazards Program