Mission Valley shook Sunday afternoon

At 3:46 p.m. Sunday, Polson experienced a small earthquake that measured 3.3 on the Richter scale. Readings from more distant stations measured the temblor at 3.7 and 3.8.

Director of the Montana Bureau of Mines and Geology, Ed Deal said from information gathered by the United States Geological Survey (USGS). The small quake occurred approximately13 miles southwest of Polson. Although the state geologists may refine the exact location as they study the quake.

"There are a series of fault lines east of Polson along the Mission Range," said Deal. "These are relatively young faults. A couple of them are only 1.6 million years old. South of the Mission Range, we show a continuation of those fault lines with movement within the last 15 years, according to the map."

The quake showed a depth of 15.9 kilometers, which is how deep it was at the hypocenter (below the surface of the earth). There are 38 stations in Montana where fault lines are detected that are monitored by the USGS. A computer program picks up the exact location of the quakes. The general vicinity of last Sunday's quake was indicated by the computer as: latitude 47 degrees, 34.01 minutes and the longitude was 114 degrees, 18.90 minutes.

"There is always a risk of major earthquake," said Deal. "But we can't predict them. The most active earthquake in Montana is the Yellowstone area. As you come north out of Yellowstone, there is a belt of fault lines that swing north to Helena and northwest from there. They are kind of scattered out, but from Helena they swing toward the northwest portion of the state."

Deal said his office received a few calls inquiring about Sunday's quake and was asked if the swarm of hundreds of small earthquakes at Mount St. Helens in Washington caused the quake in the Mission Valley.

"These small quakes were not related to any activities in St. Helens," said Deal. "However, the quakes in Alaska last year had a direct effect on the Yellowstone fault."

For more information about earthquakes in Montana, check out

www.mbmg.mtech.edu andclick on earthquake studies. Anyone who experienced Sunday's quake is encouraged to send e-mails and place their personal comments or experiences on the website.