In seismology, induced seismicity refers to earthquakes that are caused by human activity. It occurs when this activity alters the stresses and strains in the Earth's crust. Most induced seismicity is of an extremely low magnitude, and in many cases, human activity is merely the trigger for an earthquake that would have occurred naturally in any case.

There are a number of ways in which induced seismicity has been seen to occur:

Reservoirs 

The mass of water in a reservoir alters the pressure in the rock below, which can trigger earthquakes. Reservoir-induced seismic events can be relatively large compared to other forms of induced seismicity.

Mining 

Mining leaves voids that can alter the balance of forces in the rock, triggering earthquakes.

Fossil fuel extraction 

Subsidence caused by fossil fuel (oil and/or natural gas) extraction can trigger earthquakes.

Nuclear explosions 

The huge forces unleashed by nuclear weapons tests have been known to cause seismic activity.