Jose Cepeda

Hazard analysis of seismic submarine slope instability

To assess the risk associated with a submarine landslide, one must estimate the probability of slope failure and its consequences. This paper proposes a procedure to estimate the probability of earthquake-induced submarine slope failure (hazard) based on probabilistic seismic hazard analyses, ground response analyses and advanced laboratory tests. The outcomes from these analyses are treated in a probabilistic framework, with analytical simulations using mathematical techniques such as the first-order reliability method, Monte Carlo simulation and Bayesian updating. Fragility curves of slope failure during the earthquake (co-seismic) and after the earthquake (post-seismic) were developed in this study, and were shown to provide a clear and well-organized procedure to estimate the annual failure probability of a submarine slope under earthquake loading.

Analysis and Uncertainty Quantification of Dynamic Run-Out Model Parameters for Landslides

The main goals of landslide run-out modeling should be the assessment of future landslide activity with a range of potential scenarios, and the information of the local populations about the hazards in order to enable informed response measures. In recent times, numerical dynamic run-out models have been developed which can assess the velocity and extent of motion of rapid landslides such as debris flows and avalanches, flow slides and rock avalanches. These models are physically-based and solved numerically, simulating the movement of the flow using constitutive laws of fluid mechanics in one or two dimensions. Resistance parameters and release volumes are crucial for a realistic simulation of the landslide behavior, whereas it is generally difficult to measure them directly in the field. Uncertainties in the parameterization of these models yield many uncertainties concerning their frequency values, which must be addressed in a proper risk assessment. Based on the probability density functions of release volumes and friction coefficients of a given landslide model, this work aims to systematically quantify the uncertainties in the run-out modeling. The obtained distributions can be used as an input for a probabilistic methodology where the uncertainties in the release volume and friction coefficients (rheological parameters) inside the dynamic models can be addressed. This will improve the confidence of the dynamic run-out model outputs such as the distribution of deposits in the run-out area, velocities and impact pressures, important components for a risk analysis and regulatory zoning.

Correction Factors for 1-D Runout Analyses of Selected Submarine Slides

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.

Introduction: Rain Induced Landslides

With current global warming and climate change issues, numbers of rainfall induced landslides have been increasing. This session includes 9 papers that include landslide hazard analysis and monitoring programs, landslides case studies, and effects of landslides on natural slopes as well as mines. The session will discuss on how the numbers and risks of rainfall induced landslides can be reduced.