Submarine landslides in subduction zones: insights from analogue and numerical models

Submarine landslides are common features at subduction zones. Detailed analysis of bathymetry around the Japan Trench found numerous slope failures along the inflection lines in the ocean floor slope, sub-parallel to the trench (Sasaki, 2003). Since the overriding plate at the Japan Trench has no accretion of ocean floor sediments but subduction erosion, these slope failures may have strongly controlled by the surface topographic relief of the subducting plate (Sasaki, 2003). In fact, several significant submarine landslide features are believed to be formed by seamount subduction to the trench. Such mega-scale submarine landslides, which also believed due to seamount subduction, have been recognized in Nankai Trough with typical accretionary prism development. The authors have been running analogue model experiments with granular materials and numerical simulation that approximate the geologic body as particles to model the deformation of accretionary prisms. The analogue model results are further analyzed by optical image correlation technique, PIV, to extract active deformation features in detail. By using the same tectonic model for subduction margin tectonics, we examined the surface deformation process by these two techniques. The model results produce two-types of slope failures: one related to seamount subduction and the other at the thrust front. The former examples are generally mega-scale and occur at the trench-side slope of the topographic high formed after the seamount subduction. The latter ones are minor but commonly found at the active frontal thrust. Such failures may be general features and expected to be found at drill holes of IODP (e.g. NanTroSEIZE).

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