A sequence of events that occurs when two colliding plates become locked along some section of the subduction thrust (see subduction zone). There is an interseismic period lasting for hundreds of years during which the upper plate is uplifted and shortened. Eventually, the accumulated stress exceeds the strength of the fault and the locked region fails, triggering a coseismic period, lasting a matter of minutes, during which the upper plate simultaneously subsides and extends horizontally, releasing the elastic strain and causing a major earthquake.