The U.S. Geological Survey reported that an earthquake with a 4.2 magnitude rattled Cascade County near Great Falls, Mont., originating about 7.5 miles northeast of Malmstrom Air Force Base at 12:41 p.m. on Thursday. According to a public information statement put out by the National Weather Service, the quake was felt as far north as Shelby and as far south as Helena. The USGS is warning that there is a 27% chance of aftershocks. of a 3.0 higher earthquake as well as a 6% chance for one greater than 4.0.