Current practice to model the occurrence of submarine landslides is based on methods that assess the potential of site-specific failures, all with the objective of providing elements to identify and quantify regional features associated to geohazards, before a project development takes place. Also, survey data to estimate parameters required to model submarine landslides show typically limited availability, mainly because of the cost associated to offshore surveying campaigns. In this paper, a probabilistic calibration approach is introduced using Bayesian statistical inference to maximize the use of available site investigation data, and to best estimate the occurrence of a marine landslide. For this purpose, a landslide model thought for its simplicity is used to illustrate the applicability and potential of the calibration methodology. The aim is to introduce a systematic approach to produce prior probability distributions of the model parameters, based on an actual integrated marine site investigation including geological, geophysical, and geomatics data, to then compare it with a posterior probability distribution of the same model parameters, but estimated after collecting in situ soil samples and testing them in the laboratory to produce the corresponding soil strength properties. This comparison allows to explore (a) the influence of the number of in situ samples, (b) the influence of a landslide factor of safety, and (c) the influence of the soil heterogeneity, into the likelihood of the occurrence of a marine landslide. The model parameters that are considered for calibration include the initial state of the submerged and saturated soil unit weight, the thickness of the soils' unit layers, the pseudo-static seismic coefficient, and the slope angle, while the soil undrained shear strength is considered as the reference parameter to conduct the calibration (i.e., to compare model predictions vs. actual observations). Results show the potential of the proposed methodology to produce landslide geohazard maps, which are needed for the planning and design of marine infrastructure.

Seismic-induced submarine landslides pose significant risks to offshore structures. To enhance our understanding of this phenomenon, we have developed a CFD-MPM capable of simulating complete mechanisms behind earthquake induced submarine landslide. Recent centrifuge tests have demonstrated that the permeability of marine sediment is a critical factor in determining the failure mechanism of submarine landslides. Specifically, a lower permeability increases the likelihood of a slope transitioning from failure to gravity debris flow. Our CFDMPM, validated with centrifuge tests, supports this conclusion. Moreover, we conducted a sensitivity analysis of seismic-induced submarine landslides using the CFD-MPM. In the case of contractive soil, a lower permeability leads to slower dissipation of excess pore water pressure, resulting in longer submarine debris flow runouts. Additionally, in the case of softening soil, a lower permeability increases the chances of spreads as a failure mechanism, while a higher permeability favours retrogressive flow slides. This study sheds light on the diverse effects of sediment permeability on submarine landslide mechanisms, offering crucial insights for hazard assessment and mitigation strategies in offshore engineering and coastal management.