What Causes Earthquakes?
Earthquakes happen when two large pieces of the Earth’s crust suddenly slip. This causes shock waves to shake the surface of the Earth in the form of an earthquake. When an earthquake occurs the ground in the area of the quake trembles, and buildings shake.
The shaking is caused by a sudden violent movement of part of the earth’s crust. Scientists tell us that the earth’s crust is made up of giant plates of rock that slowly shift about on the hot, liquid rock in the earth’s interior.
As the huge blocks of rock rub and push against one another, great strain builds up where the plates meet. The pressure finally causes the plates to shift suddenly. Shock waves are sent in all directions, shaking the earth for miles around.
Generally before and after a large earthquake there will be smaller earthquakes. The ones that happen before are called foreshocks. The ones that happen after are called aftershocks. Scientists don’t really know if an earthquake is a foreshock until the bigger earthquake occurs.
The place where the earthquake starts, below the surface of the earth, is called the hypocenter. The place directly above this on the surface is called the epicenter. The earthquake will be the strongest at this point on the surface.