By JEFF POHJOLA
KIRO Radio

A recent swarm of earthquakes has geologists keeping a close eye on Mount Saint Helens.

The USGS says 15 small quakes, mostly in the magnitude 1 range, shook the mountain over the weekend. A spokesman at the seismology lab at the University Washington, Bill Steele, says the quakes were caused by faults and not volcanic activity.

The most powerful quake measured just 2.2 on the Richter Scale. They were about two miles deep just northwest of the volcano.

>>Check for shaking on the Northwest earthquake tracker

Steele says there were no reports the quakes were felt and the swarm dropped off Sunday.

While it wasn't alarming, Steele says an earthquake swarm near the volcano is closely watched.

The Associated Press contributed to this report.

Jeff Pohjola, 97.3 KIRO FM Reporter