Oil and Gas Extraction
A trio of major temblors between 1976 and 1984 is thought to have resulted from natural gas extraction in the Gazli natural gas field of Uzbekistan
. Above, excess gas is flared off at the Jonah natural gas field in Pinedale, Wyoming, in August 2006.
Prior to 1976, Gazli field had very little earthquake activity, according to a 1985 study in the Bulletin of the Seisomological Society of America.
But then it was hit by three large temblors in rapid succession, all of which had magnitudes in excess of 6.8.
Such earthquakes can be triggered by changes in fluid pressure in the pores of rocks, said David Simpson, president of the IRIS Consortium, a seismological research group headquartered in Washington, D.C.
In a natural gas field, such changes might come either from pumping gas out or by a process called secondary recovery, in which water or gas is injected into the rocks to enhance production, Simpson noted.
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Photograph by Joel Sartore