Earthquakes

Earthquakes can happen along any type of plate boundary. They also occur along faults which are large cracks in the earth’s crust. Most faults are associated with large plate boundaries where violent earthquakes usually occur. Causes of Earthquakes Earthquakes are caused when the tension is released from inside the crust. This happens because plates do not move smoothly - sometimes they get stuck. When this happens a great deal of pressure builds up. Eventually this pressure is released and an earthquake tends to occur. An earthquake starts deep below the earth’s surface at the focus.  The focus is the point inside the Earth's crust where the pressure is released. The epicentre of an earthquake is the position on the earth’s surface directly above its focus. The jerking movement caused by plates sticking then moving releases built-up pressure inside the Earth's crust, in the form of seismic waves. The waves spread out from the focus. The strongest waves are found near the centre of the earthquake. This means that the most severe damage caused by an earthquake will happen close to the epicentre. It is almost impossible to predict when they will occur. The effect of an earthquake depends on the depth of an earthquake as well as its magnitude.