In the early 2000s, USGS scientists including Brian Sherrod set out to further Johnson’s work and better understand the slumbering fissure. “But they didn’t document it hardly at all.” “They knew something was there,” said Sam Johnson, a retired USGS geologist who would follow up on their work. They didn’t recognize the significance of what they found. In 1985, with little concrete evidence of its existence, the pair included the possible fault on a geologic map published by the USGS. Years ago, Howard Gower and James Yount came to the Puget lowlands to study earthquake risks and stumbled on what appeared to be a fault in Island and Snohomish counties. Geological Survey first theorized that a fissure between two major blocks of the Earth’s crust might run through this slice of Puget Sound. Until much more recently, no one really understood what it could do to a region of over 4 million people.Ī pair of scientists with the U.S. Until the 1980s, no one knew SWIF existed. The quake, Murphy said, “is probably the worst thing that could happen to the county.” Unlike The Big One, scientists who have studied the southern Whidbey fault have a far less clear understanding of when the next sudden shift might hit. The same data predicted three deaths and 150 injuries in Snohomish County.Ī major southern Whidbey quake, on the other hand, could kill as many as 340 and injure 5,000 more here, according to Murphy’s estimate. Experts believe a magnitude 9.0 could happen there anytime in the next 200 years or so.ĭespite its location well offshore, a Cascadia quake would likely kill at least 10,000 and injure more than 30,000 in Washington, Murphy found. The threat to Puget Sound from a quake along the Cascadia Subduction Zone, off the coast of Washington, Oregon and California, is well documented. He combed through state and federal data to understand the risk in Snohomish County, and to help train first responders. In 2017, he began studying the possible aftermath of a major SWIF quake. This is the hypothetical scenario created by Mark Murphy of the Snohomish County Department of Emergency Management. Hundreds could die, with thousands more injured. Restoring tap water to homes could take over a year.Īlmost 5,000 residents would lose housing temporarily or permanently. Over 10,000 buildings could sustain extensive damage. Department of Homeland Security study, about 80% of state-maintained bridges in Snohomish County would be severely damaged, leaving them unusable for months or years. Under a scenario played out in a 2019 U.S. Standing becomes almost impossible as the jolts turn to rolling waves.Īround Puget Sound, it seems everyone knows about “ The Big One,” the potential magnitude 9.0 Cascadia Subduction Zone megaquake some scientists say is due any day.Ĭonsider a magnitude 7.4 quake with Everett at or near the epicenter. People stagger into the streets to avoid an avalanche of debris. Cars are stranded on islands of highway.įacades crumble off buildings along Hewitt Avenue, and some of the oldest structures collapse in a roaring cloud of dust. Water bubbles through widening cracks in the asphalt of U.S. Older buildings tilt and sink as if in quicksand. In the Snohomish River delta, sandy soil wobbles like Jell-O. Disoriented drivers wonder what’s wrong with their cars, then realize something much bigger is amiss. Bookcases and china cabinets topple, trapping people beneath. Life or death: Be prepared for a major earthquake May 14, 2021īrick chimneys cascade off rooftops.Aftermath: Infrastructure won’t fare well in a big quake May 17, 2021 Built on pudding: Can modern quake engineering prevail? May 16, 2021
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