Induced seismicity
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In seismology, induced seismicity has two meanings: intentional and unintentional.
Intentional induced seismicity or reflection seismology is the production of seismic waves by various means for the purpose of gathering subsurface images for energy and mineral exploration purposes.
Unintentional induced seismicity refers to typically minor earthquakes and tremors that are caused by human activity that alters the stresses and strains on 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:
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- Reservoir
- 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. The filling of the Katse Dam in Lesotho, and the Nurek Dam in Tajikistan is an example.[1]. In Zambia, Kariba Lake may have provoked similar effects. Some experts worry that the Three Gorges Dam in China may cause earthquakes.
- Mining
- Mining leaves voids that can alter the balance of forces in the rock. These voids may collapse producing seismic waves and minor earthquakes. Natural cavern collapse forming sinkholes would produce an essentially identical local seismic event.
- Extraction of fossil fuel and groundwater
- Subsidence caused by fossil fuel (oil and/or natural gas) and groundwater extraction can generate seismic waves and minor earthquakes.[citation needed]
