Mechanical relationship between catastrophic volcanic landslides and caldera collapses.

Large-scale sector collapses of volcanic edifices and collapse calderas represent some of the most catastrophic geological events taking place at the earth's surface. Examples of these two processes occurring simultaneously suggest that a mechanical relationship between landslides and collapse calderas may exist. We demonstrate that a caldera collapse can trigger large-scale landslides in volcanic terrains. Moderate seismic shocks caused by seismogenic slip on the ring fault on which the caldera subsidence takes place act as the driving force necessary to destabilize the volcano flank. This process 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.