Once every 14 months or so, portions of coastal British Columbia and northwestern Washington State experience a slow ground motion that, if released all at once, would generate an earthquake measuring more than 6 on the Richter scale.
That's what data from a network of Global Positioning System (GPS) equipment spanning the region show, say scientists who presented their findings at last week's annual meeting of the Seismological Society of America, held this year in Victoria, British Columbia.
Scientists discovered the region's so-called silent earthquakes when they analyzed data from the summer of 1999 (SN: 5/12/01,
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