Mechanical relationship between catastrophic volcanic landslides and caldera collapses.

Large-scale sector collapses of volcanic edifices and collapse calderas rep resent some of the most catastrophic geological events taking place at the earth's surface. Examples of these two processes occurring simultaneously s uggest that a mechanical relationship between landslides and collapse calde ras may exist. We demonstrate that a caldera collapse can trigger large-sca le landslides in volcanic terrains. Moderate seismic shocks caused by seism ogenic slip on the ring fault on which the caldera subsidence takes place a ct as the driving force necessary to destabilize the volcano flank. This pr ocess is favored on steep volcanoes and where flank strength is reduced by agents such as hydrothermal alteration, pore fluid pressure increase or the presence of weak soils.