JUNCTION, Wash. — Snoqualmie Valley residents felt a rare earthquake early Tuesday morning that registered a magnitude 3.9.
The earthquake began at 3:17 a.m. around Junction, which is about 25 miles east of Seattle and about 5 miles northeast of Fall City, the United States Geological Survey said.
"That's strong enough to certainly wake you up and shake for a few seconds. For most people probably by the time they realized it was an earthquake, it was over," Pacific Northwest Seismic Network (PNSN) Director and University of Washington Professor Harold Tobin said. "The size, I don't think there's been any damage, not that I've heard of, and I wouldn't expect any at that size."
Tobin said the earthquake happened in an area where the PNSN has seen events before. Even just a few years ago, there were several earthquakes around magnitude 3 that were felt widely.
"The distance away that people feel an earthquake and how strong it feels depend on a lot of factors actually," Tobin said. "One is distance, for sure, and it depends on the ground you're on, because the waves are different if you're on kind of soft soil versus bedrock. Softer materials tend to amplify the shaking; and also the depth of the earthquake."
Tobin said this was a relatively shallow earthquake, which can be felt more strongly.
Tremors from the earthquake were felt as far away as Oak Harbor to the northwest, Port Ludlow across the Puget Sound to the west, and Olympia to the southwest, according to resident reports.
There were also smaller aftershocks in the same area in the hours following the initial earthquake.
"There's nothing that says this earthquake is a precursor to something larger coming," Tobin said. "I don't think people should be overly concerned that it's a sign of something bigger coming. There's no reason for us to think that based on our understanding of earthquakes over time."
Still, Tobin said, Washington is earthquake country and a large earthquake is always possible. For best preparation, he advised people to secure heavy items in their homes, have a go-bag ready, and remember "drop, cover and hold on."
Did you know?
Some recent seismic activity of note in the Seattle area was not naturally caused.
A western Washington geology professor found that the tremors caused by the thousands of fans crowded into Lumen Field for Taylor Swift's "Eras Tour" show generated more seismic activity than the infamous "Beast Quake" Marshawn Lynch touchdown run for the Seahawks in 2011.
Seattle's "Swift Quake" was about twice as big as a Beast Quake, which is a magnitude difference of a 0.3 quake.