Seismic examples of composite slope failures (Offshore North West Shelf, Australia)

Abstract

This research presents a seismic geomorphological analysis of slope failures in the Exmouth Plateau, offshore Northwest Shelf of Australia, using high-quality 3D seismic data. Seismic visualization techniques and seismic attribute analysis were employed to investigate the internal architecture of the failures to infer the processes that control their styles of emplacement. The investigation shows the widespread occurrence of slope failures in which sliding and slumping laterally operate and coexist, resulting in composite products. For example, shallow-detaching, second-order slides can originate by the gravitational collapse of the over-thickened leading edge of primary slide features. This mechanism is comparable to degradation processes of thrust-uplifted strata observed along submarine fold belts and in exposed ancient foreland basins. Headscarp retrogression and progressive disaggregation of collapsing earth bodies are commonly observed in subaerial collapse systems. These seem to be common processes able to create composite slide-to-slump and slump-to-slide submarine failures observed in the NW shelf of Australia. The results of this research suggest that caution is necessary when assessing the nature of slope failures when only parts of the systems are accessible for observation.