Earthquakes are caused by the sudden release of energy when underground rock breaks and moves rapidly along faults in the Earth's crust. This usually happens due to the buildup of stress from the continuous motion of tectonic plates. When the stress exceeds the strength of the rocks, they fracture, and the stored elastic strain energy is released in the form of seismic waves, causing the ground to shake. Key points on the causes of earthquakes:
- The Earth's crust is divided into tectonic plates that are constantly moving.
- Plates can become stuck at their edges due to friction, causing pressure to build up.
- When the pressure is released suddenly, it causes an earthquake along faults (cracks in the Earth's crust) where rocks slip past each other.
- The initial breaking point underground is called the focus or hypocenter; the point on the surface directly above it is the epicenter.
- Earthquakes commonly occur at plate boundaries, especially in belts such as the Pacific "Ring of Fire."
- Earthquakes can also be triggered by volcanic activity, landslides, human activities like mining or reservoir filling, and induced seismicity from processes such as fracking.
Thus, the primary cause is the accumulation and sudden release of stress caused by movements of the Earth's tectonic plates and the resulting fault slips.
