Science
How does an earthquake happen?
An earthquake happens when stress built up in the Earth's crust is suddenly released, usually as two tectonic plates slip past each other along a fault. That sudden movement sends out waves of energy that shake the ground.
See it in motion.
Watch a 2-minute animated lesson that shows exactly how an earthquake works.
Step by step
- 1Earth's outer shell is broken into giant tectonic plates that slowly move.
- 2Where plates meet, friction can lock them together while stress keeps building.
- 3When the stress overcomes the friction, the rock suddenly slips along a fault.
- 4The released energy radiates outward as seismic waves that shake the surface.
- 5The point underground where it starts is the focus; the spot directly above is the epicenter.
Frequently asked questions
- What causes most earthquakes?
- The movement of tectonic plates. Stress builds where plates grind against each other and is released suddenly as the rock slips along a fault.
- How are earthquakes measured?
- Seismometers record the ground motion, and the energy released is expressed on a magnitude scale — each whole step up means roughly 32 times more energy.
- Can earthquakes be predicted?
- Not precisely. Scientists can map risk zones and long-term probabilities, but they can't yet say exactly when or where a specific quake will strike.