Physical properties, pore water geochemistry, 210Pb-dating of sediment cores GeoB16426-1, GeoB16427-1, GeoB16429-1

Transient geochemical signals in the slump deposit and analysis of diffusive re-equilibration of disturbed SO4**2- profiles over time constrain the triggering of the slump to the 2011 earthquake.

We propose a causal link between earthquake slip to the trench and rotational slumping above a subducting horst structure. We conclude that the earthquake-triggered slump is a leading agent for accretion of trench sediments into the forearc and hypothesize that forward growth of the prism and seaward advance of the deformation front by more than 2 km can occur, episodically, during a single-event, large mega-thrust earthquake.