Last night saw a 3.8 earthquake hit central Oklahoma, according to the US Geological Survey—one of 10 to hit the area since Friday, NBC News reports. The 3.8 quake was the most powerful of the minor quakes; it struck near the town of Guthrie, which is about 30 miles north of Oklahoma City. Its aftershocks ranged from 2.7 to 3.0. The area is a hotbed of seismic activity: It's seen more than 200 earthquakes of magnitude 3.0 or higher since January 2009, officials say, per KOCO.
What's notable is the change: There were just one to three per year between 1975 and 2008. Whether the difference is due to human or natural activity is unclear, says an expert. Either way, locals have been getting worried over frequent booming sounds. "If I’m experiencing eight of these in one day, then when does it erupt and become absolutely horrible that takes my house down?" asks one resident.