Buried North Sea landslide reveals the potential of major catastrophic landslides in rift settings

Landslides forming in active rifts are typically small. Here we use broadband seismic data to unravel an exceptionally large (340 km ² ) landslide in the buried North Sea paleorift. The landslide formed by gravity-driven collapse of a > 2.5 km high fault-generated footwall crest of crystalline basement rocks. ~300 km ³ of rocks moved ca. 8 km on a low-angle detachment, creating the largest known rift landslide worldwide. At the time of sliding, rift tectonics had transformed a low-relief denudation surface to a high relief Basin and Range-style topography. This topography developed at an early (Late Permian) stage due to rapid fault accumulation and large associated footwall uplift under arid denudation-suppressing climatic conditions. Lower Triassic burial of the collapsed crest occurred as a new rift-bounding fault, the Øygarden Fault, was established to the east. This study demonstrates that although rare, huge landslides can form in active rift settings.