CROMWELL ISLAND — A magnitude 3.1 earthquake shook the area at around 1 p.m. last Wednesday, with Flathead Lake’s Cromwell Island identified as the temblor’s epicenter.

The quake initially registered as a 2.7 on the Richter Scale, but was later revised up to a 3.1, according to Mike Stickney, director of the Earthquake Studies Office at the Montana Bureau of Mines and Geology. A couple of small aftershocks followed the event, the strongest of which had a magnitude of 1.3.

Stickney says that that part of the lake is no stranger to seismological activity.

“Earthquakes up in that area are not rare at all. Back in 1969 and again in ’71 there were swarms of earthquakes that included hundreds of events.… The biggest one was a 4.9.”

Though things have tapered off since that period of heightened activity, there is still a relatively steady string of minor rumblings.

“There have been swarms of smaller earthquakes in the Big Arm area over the past 10 years or so, but nothing bigger than a 3,” said Stickney.

Stickney said that earthquakes of such slight magnitude are rarely capable of inflicting damage on property. A total of 13 people reported feeling the quake to the United States Geological Survey website, many of whom were along the west side of the lake. Individuals in Kalispell and Polson also felt the tremor.