Earthquakes occur when there is a sudden slip or movement along a fault in the Earth's crust. This happens because tectonic plates, which make up the Earth's surface, are always slowly moving but get stuck at their edges due to friction. When the stress from this movement becomes too great, it causes the rock to break and slip abruptly, releasing stored-up elastic strain energy as seismic waves, which cause the ground to shake. The point underground where the rock first breaks is called the focus or hypocenter, and the point on the Earth's surface directly above it is called the epicenter. This release of energy results in the earthquake felt on the surface.
How Earthquakes Happen
- The Earth's crust is made of tectonic plates that move slowly.
- Plates may get stuck due to friction along faults.
- Stress builds up over time until it exceeds the friction.
- The sudden slip releases energy as seismic waves.
- This energy causes ground shaking experienced as an earthquake.
Types of Fault Movements
- Strike-slip: Plates slide past each other horizontally.
- Normal: One block moves downward relative to the other.
- Reverse (thrust): One block moves upwards over another.
Additional Causes
- Besides tectonic movement, earthquakes can also be caused by volcanic activity, landslides, and human activities like mining or nuclear tests.
This process is explained by the elastic rebound theory, where rocks deform gradually and then snap back to their original shape after the slip, resulting in an earthquake.
This overview explains how earthquakes come about through the sudden release of energy due to fault movements in the Earth's crust.
