The last time the Seattle fault ripped, it jolted shorelines and unleashed a tsunami. Now a new study suggests that quake might have rocked an even bigger area than anyone thought.
© Alan Berner/The Seattle TimesRecent UW graduate Beth Arcos works the site in Gorst Creek near Bremerton showing evidence of a 1,000-year-old tsunami following an earthquake on the Seattle fault.
Bremerton, Washington, US - Beth Arcos picked her way through muck and pickleweed just west of the Bremerton waterfront, on the trail of an ancient earthquake and tsunami.
"Here's the first evidence," the former University of Washington doctoral student said, kneeling to pluck clam shells from what used to be a tidal mud flat - but now sits well above the waterline. More than 1,000 years ago, Arcos explained, the Seattle fault let loose, lifting the ground here nearly 10 feet.
In this quiet bay, Arcos also confirmed what scientists long have suspected: The tsunami triggered by that quake walloped the coastline that is now home to Naval Base Kitsap, with its shipyards and aircraft carriers, as well as hundreds of waterfront houses and businesses.
The ground warping that Arcos measured around Bremerton was bigger than expected. That means the earthquake probably affected a wider swath of Western Washington than previously thought - which, in turn, nudges it toward the upper end of its estimated magnitude 7-7.5 range.
"It's a reminder that this is a location where we can get these big earthquakes, and that we need to plan and prepare for them," Arcos said. The results from her research were published in the June issue of the
Bulletin of the Seismological Society of America.The Seattle fault isn't a single strand, but a zone of subterranean fractures that extends across Puget Sound, passing under Seattle and reaching as far east as Issaquah. Arcos' work suggests the fault may extend farther west than previously thought, said Tim Walsh, chief hazards geologist for the Washington Department of Natural Resources.
Comment: Something is afoot here in this part of the galaxy:
Is Solar and Cosmic Radiation Playing Havoc With Life on Planet Earth?
Reign of Fire: Meteorites, Wildfires, Planetary Chaos and the Sixth Extinction