How a stuck fault can suddenly produce an earthquake
A fault can remain stuck through friction while surrounding rock slowly deforms and stores elastic energy. When the resisting strength is exceeded, part of the fault slips and releases energy as seismic waves. The shaking can be sudden even though the stress built up over a much longer period.
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Slow loading, rapid release
Movement within Earth's crust can load a fault with stress. Friction and other resistance may prevent its two sides from sliding smoothly, so nearby rock deforms instead.
When a section begins to fail, slip can spread along the fault. Some stored elastic energy is released as seismic waves, while other energy goes into frictional heating and breaking or deforming rock.
The earthquake is the rapid release, not the entire period of loading. This helps explain why gradual tectonic movement can result in abrupt shaking.
- Stress accumulates as the surrounding rock deforms.
- A fault section slips when resistance is overcome.
- Waves carry part of the released energy outward.
Fault systems are complex. Knowing that stress accumulates does not provide a reliable method for predicting the exact time of an individual earthquake.