New seismic hazard maps show two more quake faults in state

Scientists are discussing two more ways Western Washington could shake, rattle and roll.

The U.S. Geological Survey's new seismic hazard maps, released this week, show two more earthquake faults in Western Washington: one near the Canadian border, the other east of Port Angeles.

The new maps also contain some good news for Washington residents. Scientists now estimate that potential ground motion in the western United States is 30 percent lower than they previously thought for the kind of quakes caused by long-period seismic waves that would affect taller, multistory buildings.

Scientists developed these new estimates by using new ground-motion predicting models created after looking at shaking records from 173 global shallow crustal earthquakes to better understand what is happening in the western U.S.

They believe one of the newly added faults, called the Boulder Creek fault and located near Bellingham and the Canadian border, is capable of a magnitude 6.8 earthquake and has been active over the past several thousand years. Residents of Canada are in more danger from this fault than people who live in Washington state.

The other newly added fault, the Lake Creek-Boundary Creek fault, is east of Port Angeles along the Strait of Juan de Fuca and Olympic National Park. It is capable of producing a magnitude 7.4 earthquake and has been active over the past several thousand years.

Washington and Oregon have about 100 known faults. More than 1,000 earthquakes occur in Washington each year.

The February 2001 Nisqually quake, which had an epicenter northeast of Olympia, was a magnitude 6.8 quake.

The report also contains new information that a fault south of Whidbey Island is longer than previously thought, extending through Seattle's northern suburbs at least as far as Woodinville and possibly southeast to North Bend.

The fault has the highest hazard level of any fault in Western Washington and could produce a magnitude 7.5 earthquake.