what causes the earthquake?

Earthquake is caused due to the movement of tectonic plates. Earth consists of four layers out of which the the two uppermost layers, crust and the top of mantle forms a thin layer. This layer consists of pieces of rocks in the form of plates known as tectonic plates. These pieces keep on moving around which grind and scrape against each other. Sometimes the rough edges of the plates get stuck while rest of the plates keep moving.When the plates move far enough, the edges unstick causing a slip of earth's block with release of enormous energy which causes the earth surface to shake. Thus the earthquake is caused.