Regional Method to Assess Offshore Slope Stability

Abstract

The slope stability of some offshore environments can be evaluated by using only conventional acoustic profiling and short‐core sampling, followed by laboratory consolidation and strength testing. The test results are synthesized by using normalized‐parameter techniques. The normalized data are then used to calculate the critical earthquake acceleration factors or the wave heights needed to initiate failure. These process‐related parameters provide a quantitative measure of the relative stability for locations from which short cores were obtained. The method is most applicable to offshore environments of gentle relief and simple subsurface structure and is not considered a substitute for subsequent site‐specific analysis. Four sites off California and Alaska contain acoustically defined sediment failures. Calculated critical earthquake factors in these failed areas are typically lower than in adjacent unfailed areas, a result lending credence to the method.