Beginning in 2009, Oklahoma experienced a surge in seismicity. This surge was so large that its rate of magnitude 3 and larger earthquakes exceeded California’s from 2014 through 2017.
While these earthquakes have been induced by oil and gas related process, few of these earthquakes were induced by fracking. The largest earthquake known to be induced by hydraulic fracturing in Oklahoma was a M3.6 earthquakes in 2019. The largest known fracking induced earthquake in the United States was a M4.0 earthquake that occurred in Texas in 2018. The majority of earthquakes in Oklahoma are caused by the industrial practice known as "wastewater disposal". Wastewater disposal is a separate process in which fluid waste from oil and gas production is injected deep underground far below ground water or drinking water aquifers. In Oklahoma over 90% of the wastewater that is injected is a byproduct of oil extraction process and not waste frack fluid.
Learn more: USGS Induced Earthquakes