A continuous tremor has been shaking  from Vancouver Island south toward Olympia. A lead seismologist at the University of Washington told KIRO 7 they are not alarmed, but that the tremor is likely tied to the biggest quake in the Puget Sound region. Hundreds of tremors registered across the Pacific Northwest within a 25-hour span starting Monday.

The Pacific Northwest Seismic Network plotted 427 tremors on a map. “What’s happening is there’s an episode where the deep plate boundary is kind of rumbling,” said Dr. John Vidale, director of the Pacific Northwest Seismic Network. The tremor can last three weeks and happens about once a year.

It’s been shaking 30 miles under Puget Sound since Dec. 22. Unlike an earthquake map, the dots on the tremor map show readings of the same tremor. Dr. Vidale believes the tremor is related to the 4.3 earthquake that shook under Victoria, British Columbia on Dec. 30. That quake was the largest in the Puget Sound region since the Nisqually quake of 2001. FULL REPORT