Human-Induced Earthquakes from Deep-Well Injection: A Brief Overview [December 22, 2014] [open pdf - 704KB]
"Despite increasing evidence linking some deep-well disposal activities with human-induced earthquakes, only a small fraction of the more than 30,000 U.S. wastewater disposal wells appears to be associated with damaging earthquakes. The potential for damaging earthquakes caused by hydraulic fracturing itself, as opposed to deepwell injection of wastewater from oil and gas activities, appears to be much smaller. Hydraulic fracturing intentionally creates fractures in rocks, and induces microseismicity, mostly of less than magnitude 1.0, too small to feel or cause damage. In a few cases, however, fracking has led directly to earthquakes larger than magnitude 2.0, including at sites in Oklahoma, Ohio, England, and Canada. The Environmental Protection Agency's (EPA's) Underground Injection Control (UIC) program under the Safe Drinking Water Act (SDWA) regulates the subsurface injection of fluids to prevent endangerment of drinking water sources. EPA has established regulations for six classes of injection wells, including Class II wells used for the injection of fluids for enhanced oil and gas recovery and wastewater disposal. Most oil and gas states administer the UIC Class II program. The SDWA does not address seismicity, although EPA regulations for certain classes of injection wells require some evaluation of seismic risk. Such requirements do not apply to Class II wells; however, EPA has developed a framework for evaluating seismic risk when reviewing Class II permit applications in states where EPA administers this program. How Congress shapes EPA or other agency efforts to address and possibly mitigate human-caused earthquakes may be an issue in the 114th Congress."
CRS Report for Congress, R43836