Earthquake may happen naturally or by human activity. Based on their sources, earthquakes are classified in different groups.

1.    Natural events

a.     Tectonic earthquakes

b.    Volcanic earthquakes

c.     Cave-in earthquakes

d.    Oceanic earthquakes

2.    Man activity

a.     Induced earthquakes

b.    Controlled sources

Controlled event Earthquakes

Military or industry explosives or construction activities cause earthquakes which intensity and time of occur is predictable. These earthquakes are called controlled event earthquakes.

Volcanic Earthquakes

Fast motion of magma, collapse of underground channels and empty reservoirs or over pressure gases cause volcanic earthquakes.

Hypocenter of these earthquakes is between...and... Km. if they happen on the earth’s surface, they are called explosive earthquakes.

Induced Earthquakes

Water injection in to the earth or sudden change of water level in the dams near active faults cause earthquakes. The main source of these earthquakes is fast loading or unloading on the earth surface. Sefidrod earthquake in Iran was an induces earthquake and its source was sudden change in water level in Sefidrod lake.

Cave-in Earthquakes

Collapse of caves or underground channels cause earthquakes which are called Cave-in earthquakes. These earthquakes are locally important.

Tectonic Earthquakes

They have natural sources and abrupt release of potential energy at the “Crust plates” causes them.