Destabilization of Submarine Slopes by Sediment Accumulation: A One-Dimensional Sensitivity Analysis

Pratson, Lincoln F. (1) and Mello, Ulisses T.(2)

(1) Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO 80309, U.S.A.
(2) IBM Thomas J. Watson Research Center, Yorktown Heights, NY 10598

Abstract

A one-dimensional sensitivity analysis illustrates how sediment accumulation can interact with other environmental and lithologic factors to destabilize submarine slopes. In the analysis, the Gibson consolidation model for the generation of excess pore pressures via sediment accumulation is coupled to factor of safety ratios that express the balance of forces dictating three modes of slope failure: liquefaction, frictional sliding and shear failure, which can lead to normal faulting. The sensitivity experiments show that those factors that affect pore pressure (e.g., sediment accumulation rate, permeability) affect all three safety ratios registering the stability of the slope, while those that do not (e.g., seafloor slope, internal angle of friction, sediment rheology), only affect one or two of the ratios. Furthermore, for a given set of geologic conditions, the ratios can register different degrees of slope stability, ranging from stable to imminent failure. The experiments suggest that in general submarine slopes are most stable with respect to liquefaction and least stable with respect to shear failure. These results have implications for how failures are initiated (frictional sliding vs shear failure) and what information (morphological vs petrophysical) is needed to assess at least relative submarine slope stability.