An earthquake is a sudden and violent shaking of the Earth's surface caused by a rapid release of energy in the Earth's crust or lithosphere. This release of energy usually occurs due to movement along geological faults or other stress changes such as volcanic activity, resulting in seismic waves that propagate through the ground

. The point inside the Earth where the earthquake starts is called the hypocenter or focus, and the point on the surface directly above it is the epicenter. The shaking can vary in intensity from weak tremors that are barely felt to powerful quakes that cause significant destruction and loss of life

. Earthquakes occur because the Earth's outer layer, the lithosphere, is broken into tectonic plates that constantly move and interact. When the stress from these movements exceeds the strength of rocks, it causes a sudden slip along a fault line, releasing energy and causing the ground to shake

. In summary, an earthquake is the shaking of the Earth's surface caused by the sudden movement of the Earth's crust due to the release of accumulated strain energy, often along faults, producing seismic waves that can cause damage and be felt over large distances