The 1888 shoreline landslide and tsunami in Trondheimsfjorden, central Norway

The 1888 landslide and tsunami along the shore of the bay of Trondheim, central Norway, killed one person and caused major damage to port facilities. Recent bathymetric surveys, high-resolution seismic profiles and CPTU piezocone tests provide detail information about the morphology of the seafloor and landslide mechanisms, which can be used in tsunami simulations. Based on our integrated data set we suggest the 1888 sequence of events started with an initial underwater landslide near-shore, by detachment along a weak clayey sediment layer. Geomorphology indicates the landslide transformed rapidly into a debris flow, which subsequently triggered slope failures on the flanks of a deep underwater channel. One of the slope failures is associated with the triggering of the 1888 tsunami wave, with documented run-up heights of several meters. The interpreted sequence of events is supported by eyewitness testimony and further validated by slope stability analysis, slide dynamics modelling and 2D tsunami simulations.