Elastic-Rebound Theory

Elastic-rebound theory explains earthquakes as the sudden release of elastic strain energy that has slowly accumulated in rock on either side of a fault, rather than as some other independent cause. American geologist Harry Fielding Reid proposed the theory in 1910 after studying geodetic surveys of ground markers near San Francisco taken before and after the 1906 San Francisco earthquake, which showed the ground on either side of the San Andreas Fault had gradually deformed over the preceding decades. In the theory, tectonic forces bend and strain rock elastically across a locked fault over years to centuries, storing energy, until the accumulated stress exceeds the frictional strength holding the fault together, at which point the fault suddenly slips and the strained rock on each side snaps, or rebounds, back toward its unstrained shape, releasing the stored energy as seismic waves. Reid's theory remains a foundational model in seismology for understanding how faults generate earthquakes and for estimating the recurrence interval of future large earthquakes on a given fault segment from its rate of strain accumulation.