14 percent chance of megaquake hitting Seattle, experts say


    Seismograph (File photo)

    SEATTLE – There's a 14 percent chance of a magnitude 9 Cascadia earthquake hitting Seattle in the next 50 years, the U.S. Geological Survey estimates.

    "Unfortunately, we are unable to "predict" exactly when earthquakes will occur," said Alison Duvall, principal investigator with the University of Washington's M9 project and assistant professor.

    As part of the M9 project, which studies how shaking would affect the Puget Sound region in future offshore earthquakes and tsunamis, seismologists ran 50 computer simulations of various megaquake earthquake scenarios.

    "In general, we expect that the Seattle region will experience strong ground shaking... it will last approximately 100 seconds," Duvall said.

    The results confirmed that coastal areas would be hit the hardest and places like downtown Seattle would shake more than rocky mountaintops.

    To increase safety, Seattle is upgrading seismic standards for new buildings 240 feet or taller.

    Currently, there are 18 new buildings 240 feet or taller under construction and 24 proposed with the same height, according to Emporis.

    But the City still has 1,100 brick or stone buildings that lack any steel supports, making them vulnerable to collapse in an earthquake. Property owners are being pushed to make upgrades, but the high cost is the biggest stumbling block

    Seattle Public Schools is also making it a priority to make seismic improvements in 37 schools. During fall 2018, 14 projects were completed and an additional 17 projects will be completed by 2021. << Here’s the full list

    To prepare for the “Really Big One,” an earthquake warning system is being developed called ShakeAlert that uses real-time information to detect earthquakes as soon as they happen and issue a warning via cell phone to people a little farther away where the shaking hasn’t yet spread.

    “You can think of earthquakes and seismic waves a little like ripples in a pond – it takes time for them to reach points away from the original source,” said Harold Tobin, Director of the Pacific Northwest Seismic Network (PNSN) and UW professor.

    Although PNSN partnered with the U.S. Geological Survey to create the system, they have relied on the M9 project to show how much time it might take for the destructive shaking to arrive – which is about 20 seconds to well over a minute, depending on where the earthquake starts.

    “Doesn’t sound like much, but is enough for people to move to safe spots and many critical systems to be secured -- (whether that’s) hospitals, trains, bridges, electric and water systems, etc," Tobin said.

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