Morphology and mechanics of submarine spreading: A case study from the Storegga Slide

Abstract

[1] Spreading is a common type of ground failure in subaerial environments. However, this type of mass movement has hardly been documented in submarine settings. In this paper we show that spreading covers at least 25% of the Storegga Slide scar area, a giant submarine slide located offshore mid-Norway. The morphological signature of spreading is a repetitive pattern of ridges and troughs oriented perpendicular to the direction of movement. Two modes of failure can be identified: retrogressive failure of the headwall and slab failure and extension, both involving the breakup of a sediment unit into coherent blocks. These blocks are displaced downslope along planar slip surfaces. Limit equilibrium modeling indicates that loss of support and seismic loading are the main potential triggering mechanisms. The extent of displacement of the spreading sediment is controlled by gravitationally induced stress, angle of internal friction of the sediment, pore pressure escape, and friction. The resulting block movement pattern entails an exponential increase of displacement and thinning of the failing sediment with distance downslope. Sediment properties explain the remaining spatial variation of ridge and trough morphologies associated with spreading.

Terrestrial-style slow-moving earthflow kinematics in a submarine landslide complex

“…The surface roughness of landslide debris has been delineated using digital elevation models (DEMs) in terrestrial (McKean and Roering, 2004;Glenn et al, 2006), and submarine settings (Micallef et al, 2007a;Micallef et al, 2007b). McKean and Roering (2004) successfully applied 1-D, circular (2-D) and spherical (3-D) statistics to an airborne lidarderived DEM, mapping both the location and extent of a terrestrial earthflow, as well as geomorphic detail on the landslide surface.…”

Submarine slide blocks and associated soft-sediment deformation in deep-water basins: A review

“…13). Retrogressive failure leading to large run-out distances was sufficient a process to push large slide masses over ramps and steps formed in the slip surface, increasing the kinetic energy of blocks and their resulting fragmentation Micallef et al, 2007) (Fig. 13).…”

A review of marine geomorphometry, the quantitative study of the seafloor

“…current speed, vertical flow, temperature) on models of coldwater coral distribution, concluding that combining the environmental information from these two sources leads to improved predictions over the spatial scales in question. -c) show the trough depth, ridge length, and ridge spacing extracted from a MBES map of the north-eastern Storegga Slide using ridge characterization techniques (Micallef et al, 2007b). Figure d is a classification map generated by using these ridge characteristic maps as input layers in an unsupervised clustering algorithm (ISODATA).…”

“…This methodology was applied to the submarine mass movements offshore Norway to elucidate the evolution dynamics of a multi-phase submarine landslide (Fig. 7), while emphasising the potential role of gas hydrate dissociation and contourite deposition in controlling the location and extent of submarine slope failure (Micallef et al, 2009), and to improve understanding of the mechanics and triggers of spreading, also while using limit-equilibrium and mechanical modelling (Micallef et al, 2007b). The automated and objective mapping of submarine landscapes is indeed an important application of general geomorphometry, and specific techniques have been developed for the characterization of pockmarks (Harrison et al, 2011;Gafeira et al, 2012), terraces (Passaro et al, 2011), and canyons (Ismail et al, 2015).…”