PNW Coast Could Drop 6 Feet With Overdue Quake
2025-05-01T15:45:00Z
Major earthquakes typically occur every 500 years or so, but the last “Big One” to strike along the Cascadia Subduction Zone, stretching for 600 miles offshore from Northern California to Vancouver Island, came in 1700. In other words, the Pacific Northwest i…
Major earthquakes of magnitude 9 or higher typically occur every 500 years or so along the Cascadia Subduction Zone, stretching for 600 miles offshore from Northern California to Vancouver Island. The last “Big One” to strike came in 1700. But geologists estimate quakes around magnitude 8 hit the zone’s southern section every 234 years, meaning the Pacific Northwest might be due for a major earthquake—one that a new study predicts could cause land to sink dramatically and trigger serious flooding and a tsunami. “We could have a disaster on the scale of Japan 2011 or Sumatra 2004,” lead study author Tina Dura, an associate professor of natural hazards at Virginia Tech, tells the Washington Post .
“It’s the same kind of fault. It has the same capability of making a huge earthquake, tsunami, and coastal subsidence,” Dura says, In the 2004 Indian Ocean earthquake and tsunami, which killed 227,000 people, Sumatra’s land sunk by up to 6 feet, per Live Science. An earthquake with a magnitude of 8 or greater in the Cascadia Subduction Zone could cause coastal land to sink more than 6.5 feet and expand the 100-year flood plain, an area with at least a 1% chance of flooding in any given year—by 115 square miles, according to the study published Monday in PNAS. The number of residents and buildings at risk from flooding would climb 177% and 168%, respectively.
Dura tells the Post that a “Big One” could come “any day, but it might not happen till 2100.” A delay won’t make the consequences any better. With sea-level rise driven by climate change, a major earthquake in 2100 could expand the 100-year floodplain by 145 square miles, per Live Science. The number of residents and buildings at risk from flooding would climb 218% and 217%, respectively, under the most extreme scenario. Crucial infrastructure, including wastewater treatment plants, electrical substations, and municipal airports, would be affected. “My hope is just to get the word out there more so people can be prepared,” Dura tells the Post. “And we can have less impact, less loss of life and property.” (More Cascadia Fault stories.)
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