Answer in brief

Give reasons why an earthquake occurs.

An earthquake occurs when the tension in the normal movements within the earth’s crust increases leading to formation of massive waves creating trembling on the earth’s surface.

• Movements below the earth’s surface creates tension which keeps on accumulating.

• High energy is released at the place where the tension mounts up creating the center of the earthquake or the focus.

• Seismic waves scatter in all directions from the focus.

• Underground rocks can break along the fault lines created by movements of such waves which is expressed by an earthquake on the surface.

Plate boundaries are active areas of earthquakes as the plates are in constant motion.