| Popis: |
In the period between 1961 and 2008, Oklahoma, USA, averaged about two M ≥3.0 earthquakes per year, with no damage to any built infrastructure. A substantial increase in seismic activity was first observed in 2009, when there were 20 M ≥3.0 earthquakes, and activity peaked in 2015, when over 900 M ≥3.0 earthquakes occurred. Because of the unprecedented increase in seismic activity, the governor’s office of Oklahoma formed a Coordinating Council of researchers, regulators, industry, and other stakeholders in 2015. The Coordinating Council was led by the Secretary of Energy and Environment and charged with understanding and attempting to mitigate (that is, reduce, if not eliminate) induced seismicity and potential impacts. Major outcomes of the coordinated efforts included delineation of an area of interest (AOI) for seismicity in Oklahoma, modifications to underground injection control (UIC) well completion depths and injection rates into UIC wells in the AOI, development of the Oklahoma Well and Seismic Monitoring (OWSM) application used for regulatory oversight and action, modified well completion protocols, a more robust seismic network, and numerous scientific investigations and publications. Because of concerted efforts between regulators and industry, disposal into the Arbuckle Group, the primary zone for wastewater disposal, in the AOI was reduced by more than 50% though oil production continued to increase. Seismic activity decreased over a 6 yr period with 619, 302, 195, 65, 39, and 29 M ≥3.0 earthquakes occurring in 2016, 2017, 2018, 2019, 2020, and 2021, respectively. At the time of latest updates to this chapter (16 October 2022), there have been 12 M ≥3.0 earthquakes and one M ≥4.0 earthquake, so the projected total of M ≥3.0 earthquakes in 2022 is 17. Using these metrics, the coordinated efforts of Oklahoma stakeholders appear to have successfully reduced seismicity with respect to frequency and number in the range of minor but often felt (M 3.0–3.9), light (M 4.0–4.9), and moderate (M 5.0–5.9) earthquakes. So, the Oklahoma case provides examples of how stakeholder action diminished seismic hazards and how similar actions could be used to reduce induced seismicity in other areas where injections occur. |
