A magnitude 3.1 earthquake has shaken part of north-central Oklahoma.
The US Geological Survey says the quake was recorded at a depth of 3.7km.
No damage or injuries were immediately reported. Geologists say that damage is not likely in earthquakes of magnitude 4.0 or less.
Thousands of earthquakes have been recorded in Oklahoma in recent years. Many have been linked to the underground injection of wastewater from oil and natural gas production.
Scientists have also linked earthquakes in Kansas, Texas and other states to wastewater injection.
Oklahoma regulators have directed several oil and gas producers in the state to close injection wells and reduce volumes in others.
