Propagation of the Storegga tsunami in the southeastern North Sea

Numerical simulations of the 8150 BP Storegga slide event in the Norwegian Sea are necessary for understanding both landslide dynamics and tsunami propagation. Here we focus on the southern North Sea, South East of Dogger Bank, and the shores of Denmark and Germany where there have been reports of Storegga tsunami deposits. We simulate the slide using a recently developed cohesive landslide model that has demonstrated success in predicting both the extent of landslide run-out and tsunami run-up heights farther north, and we model sea surface elevations, current velocities, and arrival times of the tsunami. However, the model results rely on using an accurate bathymetry for 8150 years ago, but for this part of the southern North Sea such a palaeobathymetry is somewhat uncertain. Thus, we parametrize a continuum of bathymetric models between the present-day bathymetry through two different palaeobathymetric models, and then perform complete simulations for multiple candidate bathymetric models. For many models in which Dogger Bank is completely submerged, the shallow water in this part of the North Sea still represents a significant barrier to tsunami propagation. We compare tsunami metrics between the alternative bathymetries systematically and conclude that the tsunami surface elevations and velocities in the southeastern North Sea are probably too small to have caused erosion and significant deposition of tsunami debris along the coasts of Denmark and Germany. Instead, we reinterpret the deposits as related to the inundation of the coast during the Holocene sea level rise between 7000 and 8000 years ago.