'Myths' persist about the increase in human-caused seismic activity

http://www.eurekalert.org/pub_releases/2015-06/ssoa-p060215.php

Public Release: 9-Jun-2015
Seismological Society of America

Seismologists studying the recent dramatic upswing in earthquakes triggered by human activity want to clear up a few common misconceptions about the trend.

There is increasing evidence that these earthquakes are caused by injecting fluids from oil and gas operations deep into the earth. These human-caused earthquakes are sometimes called "induced earthquakes."

A Seismological Research Letters focus section to be published online June 10 addresses some common misconceptions about induced seismicity--the biggest of which is that it is primarily related to oil and gas recovery by hydraulic fracturing or "fracking." The focus section will appear in the July/August print issue.

Guest editor Justin Rubinstein, a scientist with the U.S. Geological Survey, explains that most of the induced earthquakes felt in the United States are from the disposal of large amounts of wastewater from oil and gas production. The majority of this wastewater is ancient ocean brine that was trapped in rock layers along with gas and oil deposits. Only a small percentage of induced seismicity comes from fracking processes that inject liquid into the ground to break up rock layers to free oil and gas for recovery.

Wastewater disposal from oil and gas operations has increased in the U.S. in the past decade, especially in states like Oklahoma where the amount of wastewater disposal doubled between 1999 and 2013.

"Wastewater disposal is expanding and waste fluids are being injected into new locations. There have been changes in production practices as well, so in some areas there is much more wastewater that needs to be disposed," Rubinstein noted.

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Seismologists studying the recent dramatic upswing in earthquakes triggered by human activity want to clear up a few common misconceptions about the trend.

There is increasing evidence that these earthquakes are caused by injecting fluids from oil and gas operations deep into the earth. These human-caused earthquakes are sometimes called "induced earthquakes."

A Seismological Research Letters focus section to be published online June 10 addresses some common misconceptions about induced seismicity--the biggest of which is that it is primarily related to oil and gas recovery by hydraulic fracturing or "fracking." The focus section will appear in the July/August print issue.

Guest editor Justin Rubinstein, a scientist with the U.S. Geological Survey, explains that most of the induced earthquakes felt in the United States are from the disposal of large amounts of wastewater from oil and gas production. The majority of this wastewater is ancient ocean brine that was trapped in rock layers along with gas and oil deposits. Only a small percentage of induced seismicity comes from fracking processes that inject liquid into the ground to break up rock layers to free oil and gas for recovery. [Is this because at this time there is less fracking than regular oil & gas wells?]

Wastewater disposal from oil and gas operations has increased in the U.S. in the past decade, especially in states like Oklahoma where the amount of wastewater disposal doubled between 1999 and 2013.

"Wastewater disposal is expanding and waste fluids are being injected into new locations. There have been changes in production practices as well, so in some areas there is much more wastewater that needs to be disposed," Rubinstein noted.

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