What health considerations are there?


Incidents involving production infrastructure and facilities

The production of shale oil and gas involves other infrastructure in addition to that found at the well site, such as pipelines (see Appendix E), processing plants, and compressor stations. Some communities have been concerned that methane leaks, releases of other airborne toxins, fires, and explosions could occur at these facilities, many of which are situated close to large population areas. In 2013, for example, dramatic floods affected oil and gas infrastructure in Colorado, releasing oil and produced water into the environment. Post-flooding monitoring concluded, however, that the volume of floodwater diluted the releases to the point that they were unlikely to pose a public health concern. 1

Can shale development operations cause earthquakes?

As discussed above, shale development operations require the disposal of a large quantity of wastewater, which is often injected into underground wells (or injection wells). Although it has long been known that certain human activities—such as underground injection, oil and gas extraction, mining, and geothermal projects—can lead to induced seismicity, 2 the magnitude of these earthquakes was thought to be too minor to pose a risk to people or property.

Since 2009, however, the number of earthquakes has spiked in the central and eastern regions of the United States at the same time that wastewater disposal from shale development has significantly increased. 3 This increase in seismic activity was remarkable, given that areas such as central and northern Oklahoma are accustomed to very few felt earthquakes. While the majority of these tremors are too minor to cause any damage, several 2011–2012 quakes in Colorado, Oklahoma, Texas, and Arkansas had magnitudes of over 5.0, resulting in some injuries and damage. 4 

According to recent studies by independent scientists and the U.S. Geological Survey (USGS), the underground injection of high volumes of produced water is associated with the increase in earthquakes in the central and eastern United States. 5, 6, 7 It should be noted, however, that there are over 150,000 approved injection wells in the United States, used for various purposes, most of which have no measurable seismic activity associated with them. Approximately 40,000 of these disposal wells are for oil and gas operations. 8 It thus appears that only a very few wastewater disposal wells used by the oil and gas industry could potentially cause earthquakes large enough to be felt on the surface. 9 The challenge is therefore identifying which injection wells, at which locations, have the potential to trigger seismicity.

A 2015 USGS and University of Colorado analysis of the relationship between wastewater injection and induced seismicity concluded that the injection rate is strongly correlated with the incidence of earthquakes. Wells injecting more than 300,000 barrels a month are much more likely to be associated with a seismic event than wells injecting at a lower rate. 10 The researchers indicated that managing the injection rate could therefore be a promising approach to reducing the likelihood of induced earthquakes.

Although there have been concerns that the process of hydraulic fracturing could trigger earthquakes, the vast majority of these tremors have been linked to wastewater injection rather than to hydraulic fracturing. 11 In its investigation of a magnitude 3.0 quake that occurred in March 2014, however, the Ohio Department of Natural Resources concluded that the incident may be due to hydraulic fracturing activity itself, and not to wastewater disposal. 12

The USGS continues to conduct research into induced seismicity with a set of studies designed to monitor and evaluate seismic events; better understand and predict the linkages between injection and earthquakes; and estimate earthquake hazards. 13 The Oklahoma Geological Survey is also conducting a study of quakes related to hydraulic fracturing activity. 14While researchers work to shed more light on the connections between seismicity and industrial activity, a work group composed of state oil and gas regulatory agencies and geological surveys has produced a guidance document for regulators on evaluating and managing the risks of induced seismicity and developing response strategies. 15 Depending on the circumstances, the mitigation options described include increasing seismic monitoring in at-risk areas, altering injection rates or pressures, introducing permit modifications, and halting injection activities.

States are addressing these induced seismicity concerns in various ways. In 2013, for example, Oklahoma put in place an evolving “traffic light” system for regulating disposal injection wells that involves a seismicity review of proposed wells, along with monitoring and increased testing of wells in areas of possible seismic activity. 16 Directives issued by the Oklahoma Corporation Commission have resulted in reductions in well depth and the volume of injections at certain wells, and have required some wells to cease injections. 17 Ohio has issued new permitting requirements for injection wells and now requires additional seismic monitoring at both injection well and shale development sites. 18, 19 Texas, on the other hand, has been more cautious about taking regulatory action, opting to wait for the results of further research on the connection between injection wells and seismicity. 20 The Texas Railroad Commission has, however, required additional testing from certain wells where links to induced seismicity have been suspected. 21  


  1. Adgate, Goldstein, and McKenzie, “Potential Public Health Hazards,” 8310.
  2. Ground Water Protection Council and Interstate Oil and Gas Compact Commission, Potential Injection-Induced Seismicity Associated with Oil & Gas Development: A Primer on Technical and Regulatory Considerations Informing Risk Management and Mitigation (2015), 1.
  3. There was an annual average of 21 earthquakes of magnitude 3 or larger (M3+) in central and eastern parts of the United States between 1973 and 2008; from 2009 through 2013, the annual rate averaged 99 M3+ earthquakes in these areas; and in 2014 alone, there were 659 M3+ earthquakes in the central and eastern states (U.S. Geological Survey, “Induced Earthquakes,” last modified September 20, 2015).
  4. M. Weingarten, S. Ge, J.W. Godt, B.A. Bekins, J.L. Rubinstein, “High-Rate Injection Is Associated with the Increase in U.S. Mid-Continent Seismicity, Science 348, no. 6241 (June 19, 2015), 1336.
  5. M. Weingarten et al., “High-Rate Injection,” 1336.
  6. F. Rall Walsh III and Mark D. Zoback, “Oklahoma’s recent earthquakes and saltwater disposal,” Science Advances 1, no. 5 (June 18, 2015).
  7. Ground Water Research and Education Foundation (GWREF), “White Paper II Summarizing a Special Session on Induced Seismicity: Assessing and Managing Risk of Induced Seismicity by Injection” (November 2013), 19.
  8. USGS, “USGS FAQs,” last modified August 19, 2015.
  9. USGS, “Induced Earthquakes.”
  10. M. Weingarten et al., “High-Rate Injection,” 1336.
  11. USGS, “How is hydraulic fracturing related to earthquakes and tremors?USGS FAQs, last modified August 19, 2015.
  12. Edward McAllister,Ohio Links Fracking to Earth Quakes, Announces Tougher Rules,” Reuters (April 11, 2014).
  13. For more information, see the United States Geological Survey, “Induced Earthquakes,” last modified September 11, 2014. 
  14. Mike Soraghan, “Oklahoma Agency Gets $1.8M to Study Seismic Links to Drilling,” E&E News, July 16, 2014.
  15. Ground Water Protection Council and Interstate Oil and Gas Compact Commission, Potential Injection-Induced Seismicity Associated with Oil & Gas Development, 4.
  16. Oklahoma Corporation Commission, “OCC Announces Next Step in Continuing Response to Earthquake Concerns” (July 17, 2015).  
  17. Oklahoma Corporation Commission, “OCC Announces Next Step.”
  18. GWREF, “White Paper II,” 27.
  19.  Edward McAllister, “Ohio Links Fracking to Earthquakes.” 
  20. GWREF, “White Paper II,” 26–27.
  21. Barclay R. Nicholson and Emery G. Richards, “Induced Seismicity Legal Issues Break New Ground,” Law360, (May 15, 2015).