Earthquakes are formed by a sudden, violent underground movement of the Earth's crust. These natural phenomena typically occur along a fault line or fault plane, which is a geological region of compressed rocks dividing crustal plates.
The Earth comprises four main layers, including the crust, mantle, outer core and inner core. The asthenosphere, located below the crust and forming the upper portion of the mantle, is the layer where the tectonic plates float, glide and held together by a fault's frictional force. Due to the intense pressure that builds underneath the asthenosphere, the plates eventually shift, slip past one another and rupture the fault. This instantaneous motion causes the release of tremendous amounts of energy in the form of seismic waves. The spot where the tremor originated underground is called the hypocenter, while the epicenter lies directly above it. The seismic waves then propagate outwards and are felt along the surface of the Earth, often by a destructive force. The most catastrophic earthquakes happen close to plate boundaries. These regions are where tectonic plates converge, diverge and shear.
There is no currently known device that correctly predicts when an earthquake may occur as of 2014. Although various methods of forecasting quakes have been attempted by many scientists, none have been feasible.