# 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.