Oilfield waste arrives by tanker truck at a wastewater disposal facility near Platteville, Colo. After removal of solids and oil, the wastewater is injected into a deep well for permanent storage underground. Photo by Bill Ellsworth, USGS.
Within the central and eastern United States, the number of earthquakes has increased dramatically over the past few years. More than 300 earthquakes above a magnitude 3.0 occurred in the three years from 2010–2012, compared with an average rate of 21 events per year observed from 1967–2000. These earthquakes are fairly small — large enough to have been felt by many people, yet small enough to rarely have caused damage.
This increase in earthquakes prompts two important questions:
- Are they natural, or man-made?
- What should be done in the future as we address the causes and consequences of these events to reduce associated risks?
A team of USGS scientists led by Bill Ellsworth analyzed changes in the rate of earthquake occurrence using large USGS databases of earthquakes recorded since 1970. The increase in seismicity has been found to coincide with the injection of wastewater in deep disposal wells in several locations, including Colorado, Texas, Arkansas, Oklahoma and Ohio. Much of this wastewater is a byproduct of oil and gas production and is routinely disposed of by injection into wells specifically designed and approved for this purpose.
Hydraulic fracturing, commonly known as “fracking,” does not appear to be linked to the increased rate of magnitude 3 and larger earthquakes.
Although wastewater injection has not yet been linked to large earthquakes (M6+), scientists cannot eliminate the possibility. It does appear that wastewater disposal induced the M5.3 Raton Basin, Colorado earthquake in 2011 as well as the M5.6 quake that struck Prague, Oklahoma in 2011, leading to a few injuries and damage to more than a dozen homes.
Cumulative number of earthquakes with a magnitude of 3.0 or larger in the central and eastern United States, 1970–2013. The dashed line corresponds to the long-term rate of 20.2 earthquakes per year, with an increase in the rate of earthquakes starting around 2009.
Science or Soundbite? Shale Gas, Hydraulic Fracturing, and Induced Earthquakes
USGS scientists Doug Duncan, Dennis Risser, and Bill Leith discuss the opportunities and impact associated with hydraulic fracturing in this 53-minute video.
Bill Ellsworth discusses the science behind induced earthquakes.
Current and Future Research
The USGS is coordinating with other federal agencies, including the EPA and Department of Energy, to better understand the occurrence of induced seismicity through both internal research and by funding university-based research with a focus on injection-induced earthquakes from wastewater disposal technologies. For instance, USGS and its university partners have deployed seismometers at sites of known or possible injection-induced earthquakes in Arkansas, Colorado, Ohio, Oklahoma and Texas. The USGS is also monitoring seismicity associated with a geologic carbon dioxide sequestration pilot project at Decatur, Illinois, and is working with industry, academia and other government agencies to study seismicity associated with geothermal energy development and production in California and Nevada.
Evidence from some case histories suggests that the magnitude of the largest earthquake tends to increase as the total volume of injected wastewater increases. Injection pressure and rate of injection may also be factors. More research is needed to determine answers to these important questions.
- USGS Science Features: Man-Made Earthquakes Update
- FAQs: Earthquakes Induced by Fluid Injection
- Department of Energy: About Induced Seismicity
- Department of Interior: Is the Recent Increase in Felt Earthquakes in the Central US Natural or Man-made?
- USGS Energy Program: Geologic Carbon Sequestration
- Reference List
- Bill Ellsworth
- Art McGarr
- Justin Rubinstein