USGS Study: Human Activity ‘Certainly’ Cause of Increased Seismic Activity

The State Journal
6 April 2012
By Taylor Kuykendall, Reporter

A new study suggests manmade causes, specifically underground waste injection from fuel extraction industries, are "almost certainly" the cause of an uptick in seismic activity.

An abstract of the study, conducted by the U.S. Geological Survey, became available this week. The full study will be presented at an annual meeting of the Seismological Society of America.

The group acknowledges "a remarkable increase in the rate of (magnitude 3.0) and greater earthquakes" in the United States.

"While the seismicity rate changes described here are almost certainly manmade, it remains to be determined how they are related to either changes in extraction methodologies or the rate of oil and gas production," the abstract states.

A direct link to oil and gas production activities is not definitively drawn in the abstract, but it is considered as a cause of the quakes.

"The acceleration in activity that began in 2009 appears to involve a combination of source regions of oil and gas production, including the Guy, Arkansas region, and in central and southern Oklahoma," the authors wrote.

The USGS scientists cite another study that provided "strong evidence" that linked seismic activity in Arkansas to deep wastewater injection wells. Those wells are used to dispose of hydraulic fracturing fluid that is used to increase production in shale gas and oil plays.

The study looks at an increase in annual recorded earthquakes from 1.2 per year in the past 50 years to more than 25 per year since 2009.

"A naturally-occurring rate change of this magnitude is unprecedented outside of volcanic settings or in the absence of a main shock, of which there were neither in this region," the abstract states.

The relationship between shale drilling activity and increased seismic activity has received much attention in recent years. Increased activity in shale gas fields, attributed to lower gas prices and advancing technology, has unlocked resources in new geographical regions.

With the new activity has come a host of new concerns the industry and its opponents continue to debate.

While the process of hydraulic fracturing has been at the center of the debate, the seismicity concerns actually stem from disposal of the water and chemicals into deep underground storage.

In the Fayetteville shale in Arkansas, officials banned wastewater injection across a wide swath of that play because of increasing numbers of earthquakes. About four months ago, Ohio officials ordered closure or suspension of five such wastewater storage wells until investigators can examine a link between seismic activity in Ohio and the wells.