Correction factors for 1-D runout analyses of selected submarine slides

Abstract

Numerical modelling of submarine mass movements is often used to estimate gravity mass flow runout distances, velocities, and the final shape of the sediments in offshore geohazards studies. This paper proposes an approach for the use of numerical models in a practical way, based on calibration against back analyses of known events, to obtain meaningful and reliable results. The proposed approach consists of estimating correction factors that quantify the approximations incurred by the numerical modelling, assuming that the input anchoring facts (i.e. geometrical, geotechnical and rheological information) are based on reliable information, therefore the difference between field evidence and simulations is merely due to the limitations of the numerical model. The approach is exemplified in the paper by simulating submarine debris flows, focused on runout distances, using the numerical model BING with the bilinear rheological model. The anchoring facts are obtained from a database of seafloor slope stability and empirical correlations. The results show the need to assess the level of uncertainty of the assumed anchoring facts in order to narrow the range of the proposed correction factors and use them for predicting runout distances in practical applications. At present the estimated correction factors range from 0.60 to 1.10.