Earthquakes happen primarily due to the sudden breaking and slipping of rocks underground along faults, which are fractures between blocks of rock. This sudden movement releases stored elastic strain energy, causing seismic waves that make the ground shake. The rocks on either side of a fault slowly deform over time due to tectonic forces, and when the stress overcomes the friction holding the rocks together, the rock breaks and slips, producing an earthquake. Key points about how earthquakes happen:
- The Earth's crust is made up of tectonic plates that move slowly.
- Most earthquakes occur along the edges of these plates where they collide or slide past each other.
- Stress builds up over time as the plates move but get stuck due to friction.
- When the stress is high enough, the rocks break suddenly and slip along the fault.
- The point underground where the rock first breaks is called the focus or hypocenter; the point above it on the surface is the epicenter.
- The released energy travels as seismic waves, causing the shaking felt during an earthquake.
This process is also called the elastic-rebound theory, describing the build- up and sudden release of stress that leads to earthquakes.
