During 2017, Oklahoma and southern Kansas experienced Mw 3+ earthquakes more frequently than in California. Although the annual count of earthquakes in the Oklahoma/Kansas area has declined since peaking in 2015, the rate of earthquake occurrence is still extremely high. More than 50 events (Mw 3+) have occurred since the start of 2018, including events of Mw 4.6 and Mw 4.5 during the first weeks of April, with shaking strong enough to be felt in Oklahoma City.
In Oklahoma and other parts of the Central and Eastern United States, research studies have linked the increased occurrence of earthquakes to oilfield wastewater injection. Damage has mostly been minimal, but the ground shaking occurring from events greater than or equal to Mw5 could have produced extensive damage had comparable events occurred in more greatly populated areas of the state.
In 2016, the United States Geological Survey (USGS) released their first short-term forecast for seismic hazard — this was meant to capture the increased (but potentially transient) nature of this hazard, and the forecast emphasized that the seismic hazard in Oklahoma is comparable to that of California. Since the first one-year forecast in 2016, the USGS has released subsequent forecasts for 2017 and now for 2018.