Assessment of relative slope stability of Kodiak shelf, Alaska, using high‐resolution acoustic profiling data

Abstract

The use of marine high-resolution geophysical profiling data, seafloor soil samples, and accepted land-based methods of analysis have provided a means of assessing the regional geotechnical conditions and relative slope stability of the portion of the Gulf of Alaska Continental Margin known as the Kodiak Shelf. Eight distinct types of soils were recognized in the study; the seafloor distribution of these indicates a complex geotechnical setting. Each soil unit was interpreted as having a distinct suite of geotechnical properties and potential foundation engineering problems. Seven categories of relative slope stability were defined and mapped. These categories range from "highest stability" to "lowest stability," and are based on the degree of slope of the seafloor, type of soil underlying the slope, and evidence of mass movement. The results of the analysis indicate that the highest potential for soil failure exists on (1) the slopes forming boundaries between the submarine banks and the broad sea valleys, and (2) the upper portion of the continental slope, where evidence of past slope failure is common. Also of concern are gently sloping areas near the edges of submarine banks where evidence of possible tension cracks and slow downhill creep was found.

Earthquake hazards in the offshore environment

“…Areal assessments of slope stability have been prepared for several earthquake-prone regions, both onshore (for example, Nilsen and others, 1979) and offshore (for example, Self and Mahmood, 1977). The variation in relative slope stability for part of the Kodiak shelf off Alaska is shown in fig.…”

“…The variation in relative slope stability for part of the Kodiak shelf off Alaska is shown in fig. 40, using a fivefold classification of relative stability (table 2; Self and Mahmood, 1977). Classification of stability is based on three considerations: soil type, steepness of slope, and evidence of past slope failure.…”