graphic of how a collapse/explosion event sequence

A generalized graphic of how a collapse/explosion event sequence can occur. The upper graphic represents a cross-section of the crater filled with rock rubble and the lower graphic is an example of a typical number of earthquakes observed during a particular phase of the collapse/explosion cycle. Initially, the piston is supported by the magma reservoir. It is stable and there is very low seismicity. Second, as magma drains, stress on the faults increases and there is an earthquake swarm on the caldera ring faults. Third, the piston collapses down from its own weight. A large collapse earthquake occurs and a plume can result.