Earthquakes Caused by People

Can humans alter or create seismic activity, and how?

There has been a long history of the activities of people causing earthquakes, for which the expression used is that a human activity has “induced” an earthquake, or more simply “induced seismicity”. Although induced earthquakes are nowhere near as powerful as the largest natural earthquakes, some of them have been big enough to cause damage. Far more numerous induced earthquakes have released small amounts of energy and caused low degrees of shaking with little or no damage.

 To explain how a human activity might cause an earthquake, we start with the general reason thought to be the cause of all earthquakes: stress increases enough to move a block of rock that is adjacent to a fault. Mining activities, oil and gas development and production, injection of wastewater to store it underground, and groundwater management are all activities that have been ongoing for decades or centuries, which remove rock or fluids from – or add fluids to – underground. These common and widespread activities may progressively change stress or they may change the strength of fault zones within the rock.

 Since 1859, people have drilled deep boreholes into rock throughout North America without inducing earthquakes. In New York state alone, it has been estimated that far more than 60,000  wells for oil and gas exploration or production were drilled, and those did not induce earthquakes. The change of activities during the last 70 years that led to a growth nationally in the frequency of induced earthquakes mostly relates to pumping very large amounts of water into rocks. For instance, disposal of liquid hazardous waste by injecting it into a 12,000 ft deep well at a U.S. army facility in Colorado caused earthquakes from 1962–1970, with three earthquakes exceeding ML 5.1 in 1967. Particularly abundant in the last decade have been earthquakes induced by the injection of wastewater into rocks in Oklahoma and Texas; the water was a by-product of producing oil.

 Mining can induce small earthquakes by increasing or shifting the stresses just enough to cause the rocks to shift their position with a sudden release of energy, causing seismic waves.