PORTLAND -- A 4.3 earthquake hit the Mt. St. Helens area about 10:35 a.m. Monday, followed by 30 aftershocks, according to a USGS seismologist.
USGS Seismologist Seth Moran told KGW the quake was centered near the Johnston Ridge Observatory, and registered on seismic devices as far away as Mt. Rainier and at Timberline Lodge.
Moran said the seismic event lasted about three to five seconds, and shaking from the quake lasted up to three minutes. He said there were at least 30 aftershocks.
The 4.3 quake (pictured on the seismograph), originally rated as only a 3.3 magnitude event, happened at 10:35 a.m., about six miles north and northwest of the volcano and about three miles deep.
It was followed by a 2.8 quake at 10:37 a.m., about seven miles north and northwest of the volcano.
A quake of 2.3 was recorded at 11:35 a.m., about six miles north and northwest of the volcano but seismographs recorded six others through about 12:20 p.m. registering just above 1.
Emergency dispatchers from Clark, Cowlitz and Skamania counties all got calls reporting the quake, but no reports of any damage.
Bill Steele of the University of Washington seismology lab in Seattle said there were no signs of volcanic activity. The quakes could represent changes in the stress field at the volcano, he told AP.
KGW received reports from a number of residents who said they felt the quake, ranging from Vancouver to Troutdale to as far south as the Sunnyside area of Clackamas. The USGS web site showed more than 700 reports in the region from people who felt the quake.
More: Who felt the quake
Doug Phillips lives near the Clark County Fairgrounds at I-5 and I-205 and said he felt the quake for 10 to 15 seconds.
Nate Boris said he felt it in Hood River. Viki in Kalama said her whole house was shaking. Renee Bell reported that the quake shook her computer table in West Linn.
Debby Southworth told KGW that "I just felt a shift and my entire house shook. The windchimes on my front porch chimed too."
The USGS wants to know - did you feel it?
Live Webcam: Mt. St. Helens (weather sensitive)
A swarm of earthquakes were reported within the Mount St. Helens National Volcanic Monument the last week of January ranging from magnitude 1.3 to 2.6.
Scientists said the quakes occurred in the St. Helens seismic zone, which is a series of tectonic faults which runs underneath Mount St. Helens.
A spokesman at the seismology lab at the University Washington, Bill Steele, said those quakes were caused by faults and not volcanic activity. He added that they were about two miles deep, just northwest of the volcano and no one had reported that they felt the earthquakes.
ARCHIVE: 1980 Eruption of Mt. St. Helens