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. A few sites regularly have larger quakes, such as The Geysers geothermal plant, which in the past 5 years has averaged 2 M4 events and 15 M3 events every year. There are a many of ways in which induced seismicity has been seen to occur. In the past several years, some energy technologies that inject or extract fluid from the Earth, such as oil and gas extraction and geothermal energy development, have been found or suspected to cause seismic events. Some energy technologies also produce wastes that may be managed through disposal or storage by injection deep into the ground. For example, waste water from oil and gas production and carbon dioxide from a variety of industrial processes may be managed through underground injection.