Small quake rattles region

DIXON — Slight geological movement caused a widespread fuss in southern Lake County last Friday, with residents claiming the small quake caused a sonic-boom-like noise and the ground to shake.

A minor earthquake rattled the Sanders County town of Dixon just after 9 a.m. and registered 3.2 on the Richter scale, according to the U.S. Geological Survey. Reports to the USGS also allege that the quake was felt as far north as Polson and as far south as Missoula.

However, those reports from Polson and Missoula were not registered by the USGS until well after the quake had been reported by local media, and there were individuals in the affected regions saying they hadn’t felt anything at all.

While the Richter scale considers a 3.2 earthquake on the line of even being discernible by human beings, plenty of reports streamed into the organization’s website from Lake County. The USGS has 18 reports from the county, with the most being 10 from Charlo. A report was also made from Superior.

These types of earthquakes are quite common, with over 130,000 3.0-3.9 magnitude quakes happening worldwide every year. No damage occurs from quakes these size. Usually noticeable shaking and rattling noises, the kind of things reported by Lake County residences, don’t occur unless it’s a 4.0 or higher earthquake.

Some people from Lake County reported hearing a large booming noise, akin to a sonic boom, while others claimed it had felt like a car had hit their residence.

The “boom” phenomenon is something that the USGS has recorded before, saying that it usually comes from small, shallow earthquakes. There is no known fault line around Dixon, but there is a 15,000-year-old line that runs the length of the Mission Mountains.

These types of booms were also heard in Spokane in 2001 when a swarm of small quakes hit the Washington state city and were also estimated to be shallow, probably only a mile or two deep.

No damage was reported, since most quakes have to be 5.0 or higher on the Richter scale to cause major property damage.

This is the third time that a small quake has hit Western Montana, a 3.5 magnitude earthquake was recorded 14 miles away from Clinton on Dec. 14 after a 3.3 quake had hit near the same town on Nov. 3.