EARTHQUAKE.

•Earthquake is the shaking or vibration of the earth’s crust due to the sudden and rapid displacement of rocks along the line of weakness called fault plane.

The displacement of rocks can be caused by;

•Faulting of the earth caused by plate movement where one plate slides over or past another plate.

•Volcanism, due to the fact that magma moves under influence intense pressure from within the earth’s interior.

•Mass movement like landslides and rock fall can cause the displacement of rocks at local scale.

•Falling of objects from the atmosphere such as meteorites.

•Man’s influence through his activities such as quarrying rocks using explosives like dynamite, transport vessels like trains and heavy trucks.

•Movements of animals in big number cause earthquake but at local scale.

•A fault plane is an underground surface along which the rocks breaks and move.

•The shaking is caused by a series of shock waves called seismic waves.

The point where seismic waves are originated/start is called seismic focus

Epicenter

•The point on the earth’s surface vertical above the seismic focus is called epicenter. 

•Epicenter receives the shocks first and it is here where maximum destruction takes place.

•  Seismic waves are waves of energy that travel through the earth’s layers and are the causer of shaking of the Earth’s crust.

•They can be categorized into two broad groups; body waves and surface waves.

•Body waves are those that travel through the crust.

• They are of two categories ; primary waves (P-waves) and secondary waves (S-waves).