Hydromechanical Earthquake Nucleation Model Forecasts Onset, Peak, and Falling Rates of Induced Seismicity in Oklahoma and Kansas

• Published in: Geophysical research letters 2018-04, Vol.45 (7), p.2963-2975
• Main Authors: Norbeck, J. H., Rubinstein, J. L.
• Format: Article
• Language: English
• Subjects: Aquifers; Computational fluid dynamics; Disposal wells; Earthquake forecasting; earthquake hazard; Earthquake prediction; Earthquakes; Fluid flow; Geological hazards; geomechanics; Hazard assessment; Hydrology; induced seismicity; Injection; Mathematical models; Mitigation; Natural gas; Nucleation; Oil and gas industry; Physics; rate‐and‐state friction; Saline water; Seismic activity; Seismic analysis; Seismic hazard; Seismic response; Seismicity; Sequencing
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1002/2017GL076562

The earthquake activity in Oklahoma and Kansas that began in 2008 reflects the most widespread instance of induced seismicity observed to date. We develop a reservoir model to calculate the hydrologic conditions associated with the activity of 902 saltwater disposal wells injecting into the Arbuckle aquifer. Estimates of basement fault stressing conditions inform a rate‐and‐state friction earthquake nucleation model to forecast the seismic response to injection. Our model replicates many salient features of the induced earthquake sequence, including the onset of seismicity, the timing of the peak seismicity rate, and the reduction in seismicity following decreased disposal activity. We present evidence for variable time lags between changes in injection and seismicity rates, consistent with the prediction from rate‐and‐state theory that seismicity rate transients occur over timescales inversely proportional to stressing rate. Given the efficacy of the hydromechanical model, as confirmed through a likelihood statistical test, the results of this study support broader integration of earthquake physics within seismic hazard analysis. Plain Language Summary Earthquake activity has surged in parts of Oklahoma and Kansas, a region of the United States that historically has remained tectonically inactive. Three earthquakes with magnitude equal to or larger than 5 occurred in 2016, and researchers believe the seismic hazard in this part of the country remains high. The decade‐long earthquake sequence has been attributed to subsurface disposal of salt water related to oil and gas industrial activity. In this study, we develop a model based on fluid flow and earthquake physics to link historic injection trends with the observed patterns in seismicity. Our model reproduces important characteristics of the earthquake sequences, providing an improved understanding of the fundamental processes that control induced seismicity. Our study has implications for informing induced seismicity mitigation strategies in a region currently experiencing elevated seismic hazard. Key Points We estimate basement fault stressing conditions throughout a 300 km region using 20+ years of saltwater injection data We forecast induced seismicity across a broad range of spatial scales using a rate‐and‐state friction earthquake nucleation model A likelihood test confirms that our hydromechanical forecasts can be more accurate than methods based on extrapolations of past seismicity