MyNorthwest.com staff

Hundreds felt the ground move around the Northwest Monday morning after a 4.3 magnitude earthquake struck 9 kilometers north of Mount St. Helens.

"It was pretty shallow," said Bill Steele, Director of Information Services with the University of Washington Seismology Lab, "a depth of about five kilometers."

"We're getting a lot of aftershocks," Steele said. The lab is also getting a fair amount of reports from people that felt them. Within a half hour of the initial quake (at about 10:35 a.m.), 310 reports had already rolled in, saying they had felt something.

The aftershocks have been relatively large, "At least two greater than magnitude 2.0, perhaps more, and then a lot of little ones," said Steele. "In a normal main-shock/after shock sequence, the first hours you'll get the most earthquakes, and then sloping off pretty dramatically after that."

There have been at least nine aftershocks in the area since the 4.3 magnitude quake.

The area near Mount St. Helens has a history of earthquake events that could go on for weeks. But Steele said, "It's a little early to say."

Alyssa Kleven, MyNorthwest.com Editor

You might also be interested in:

• Check the earthquake tracker