LAUSR

Abstract Submarine landslides in the continental slopes of passive margins are recognized as coastal hazards capable of generating tsunami waves. Potential submarine landslide-prone zones in the slope regions can be identified from preliminary geophysical investigations. In the present study, we used multibeam bathymetry and sub-bottom profiling data to study the slope morphology of Palar Basin, off Chennai, covering an area of 3500 km 2 between 300 m and 3300 m water depths. The continental slope of Palar Basin is very steep (mean slope gradient, 38°) and are marked by a series of cracks parallel to the outer shelf. The identified cracks were up to 130 m deep, 10 km long and resembled “crown cracks” that often act as precursors for submarine landslides. These cracks were either a consequence of fault slips or gas hydrate dissociation or a combination of both. One of the wide crack observed was accompanied by a slump with a run-out distance of 1.6 km. Generally, these cracks are suspected of generating slope failures along a glide plane, if the preconditioning factors are favourable. In addition to these surface expressions, five distinct submarine landslides, which are ‘disintegrative’ in nature were also found. The disintegrative landslides have curved head scarps and were on average 2.70 km wide and 1.25 km long. Multiple side-walls indicated that failures might have occurred as multiple events and probably caused by over steepening of the continental slope. Based on the crack system and several failures identified along the margin, we marked probable ‘landslide susceptible zones’ in the region.