Oklahoma experiences largest earthquake during ongoing regional wastewater injection hazard mitigation efforts

• Published in: Geophysical research letters Vol. 44; no. 2; pp. 711 - 717
• Main Authors: Yeck, W. L., Hayes, G. P., McNamara, D. E., Rubinstein, J. L., Barnhart, W. D., Earle, P. S., Benz, H. M.
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 28-01-2017
• Subjects: anthropogenic; Basements; Basins; Computational fluid dynamics; earthquake; Earthquakes; Energy; Fault zones; Fluid injection; Fluids; Gas production; Geological faults; Geological hazards; Geophysics; Hazard mitigation; Hydraulic fracturing; induced; Injection; Locations (working); Mitigation; Modelling; Natural gas; Oil; Oil and gas production; Oklahoma; Plate tectonics; Seismic activity; Seismic hazard; Seismicity; Seismology; Sequencing; Slip; Tensors; Waste water; United States > US; Oklahoma; USA, Oklahoma
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1002/2016GL071685

The 3 September 2016, Mw 5.8 Pawnee earthquake was the largest recorded earthquake in the state of Oklahoma. Seismic and geodetic observations of the Pawnee sequence, including precise hypocenter locations and moment tensor modeling, shows that the Pawnee earthquake occurred on a previously unknown left‐lateral strike‐slip basement fault that intersects the mapped right‐lateral Labette fault zone. The Pawnee earthquake is part of an unprecedented increase in the earthquake rate in Oklahoma that is largely considered the result of the deep injection of waste fluids from oil and gas production. If this is, indeed, the case for the M5.8 Pawnee earthquake, then this would be the largest event to have been induced by fluid injection. Since 2015, Oklahoma has undergone wide‐scale mitigation efforts primarily aimed at reducing injection volumes. Thus far in 2016, the rate of M3 and greater earthquakes has decreased as compared to 2015, while the cumulative moment—or energy released from earthquakes—has increased. This highlights the difficulty in earthquake hazard mitigation efforts given the poorly understood long‐term diffusive effects of wastewater injection and their connection to seismicity.
Key Points
The 3 September 2016, Mw 5.8 Pawnee earthquake is the largest event recorded in Oklahoma, rupturing along a previously unmapped basement fault
In 2016, the rate of M3 and greater earthquakes in Oklahoma has decreased, but the cumulative moment has increased
Observations from this and other Oklahoma earthquakes point to the difficulty in mitigation after years of fluid injection