Slope Failures: Quantifying Frequencies and Volumes and Identifying a Potential Trigger Mechanism-Paper

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The study examines how past submarine slope failures can inform offshore geohazard assessments, particularly estimates of failure frequency, volume, run-out, and potential impacts on structures. At a deepwater, aseismic site, researchers combined autonomous underwater vehicle sub-bottom profiler (SBP) data with geotechnical cores and radiocarbon-based dating to characterize mass transport deposits (MTDs) in the upper sediments.<br /><br />SBP interpretation identified and mapped 204 MTDs, with estimated thicknesses, areas, volumes, and age ranges. Core samples revealed that MTDs were generally thinner and more frequent than indicated by SBP data. A single deposit interpreted in SBP records could comprise several thin, stacked deposits in a core; some core-identified MTDs were not apparent in nearby SBP data. These differences reflect the SBP’s limited vertical resolution and spatial coverage, while cores provide detailed observations at only a few locations. Combining the datasets can therefore improve estimates of failure history, although uncertainties remain.<br /><br />The greatest MTD frequency occurred approximately 15,450–19,540 years ago, and both frequency and volume declined toward the present. No MTDs were identified in either dataset within the past 8,233 years. The authors associate past failures with sedimentation rates: during lower sea levels, sedimentation was higher and failures more frequent and voluminous; as sea level rose, sedimentation and failure frequency declined. They propose high sedimentation rates as the likely failure trigger at the site.<br /><br />The findings underscore the value of reconciling geophysical and core interpretations when developing slope-stability and debris-impact assessments.

Keywords

submarine slope failure

offshore geohazard

mass transport deposits

sub-bottom profiler

geotechnical cores

radiocarbon dating

failure frequency

run-out

sedimentation rates

slope stability