A small, deep earthquake centered northeast of Mossyrock shook houses and was felt across Western Washington this morning.
According to the Pacific Northwest Seismic Network, the 4.2-magnitude quake occurred at 7:51 a.m. and was centered three miles northeast of Mossyrock and seven miles west of Morton. A press release from Lewis County Emergency Management said no damage has been reported, but several people — especially in central and eastern Lewis County — reported hearing a loud banging noise and feeling their homes shaking.
“It was a strong, loud boom, and I thought maybe a plane crashed or something,” said Don Portnoy, who said he lives off Pigeon Springs Road in Onalaska. “At first I couldn’t figure out what the heck it was, but then it dawned on me it’s gotta be an earthquake.”
Portnoy said there was no damage at his house, but the temblor initially scared him as his home is located close to the Newaukum River.
“It was pretty jarring,” Portnoy said. “I live down by a river so we felt it pretty good.”
John Vidale, director of the Pacific Northwest Seismic Network, said as of 9:30 a.m. that 1,113 people had submitted reports of feeling the earthquake across Washington and Oregon. Vidale said he expected more reports to come in throughout the day.
Geophysicists in Seattle’s USGS office and the National Earthquake Information Center in Golden, Colo., were reviewing the earthquake late this morning, with further seismographic reports indicating the quake could have reached 4.2 in magnitude. Seth Moran, a USGS seismologist based out of the Cascade Volcano Observatory in Vancouver, Wash., said some people reported feeling two earthquakes, but that was because of a wave created by just one seismic event.
“We had some reports close to the epicenter of people that thought they felt two quakes, which is rather interesting,” Moran said. “That part of east Lewis County is in one of the most seismically active areas of Washington, so it’s not uncommon to feel a decent amount of activity.”
Moran said the communities of Mossyrock and Morton lie on the northern end of what geologists call the Mount St. Helens Seismic Zone, an area of “historically higher” earthquake activity than the rest of Washington state — but that doesn’t necessarily mean the earth underneath the volcano that blew in 1980 is gearing up for an encore performance 30 years later.
“We don’t see threes or fours in terms of magnitude often, but the earth is active in that area,” Moran said. “Today’s quake isn’t any sort of harbinger of activity on the mountain, though, so that’s good news.”
Residents as far away as Seattle and Portland reported feeling the earthquake because the earthquake was “fairly deep,” Moran said. He said seismologists would continue to monitor data through the day and would have a more thorough earthquake report later in the day.
The quake was located just north of Mossyrock Dam, according to the USGS website. Tacoma Power spokesperson Chris Gleason told The Chronicle engineers were sent to check the Mossyrock and Mayfield dams for any sort of impact from the earthquake.
“It’s a routine procedure we do after any earthquake that can be felt in that area,” Gleason said.
The Mossyrock and Morton area was the center of a 5.1-magnitude earthquake in 1981, according to the USGS. Western Washington’s most notable recent earthquake occurred in 2001 as the 6.8-magnitude Nisqually Earthquake, centered about 11 miles northeast of Olympia, damaged the Capitol dome, buildings in Seattle and plasterwork in the Twin Cities.
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Christopher Brewer: (360) 807-8235
