So, there’s this study that says a massive earthquake in the Cascadia region of the Pacific Northwest could cause the ground near the coast to sink by up to 6.6 feet (2 meters). And get this – when you add in rising sea levels due to climate change, it could lead to some serious long-term flooding issues for areas in northern California, Washington, and Oregon. The study predicts that by 2100, the amount of land in the 100-year floodplain in the Pacific Northwest could triple.
Tina Dura, a coastal geologist at Virginia Tech who spearheaded the research, mentioned to Live Science that while we often hear about tsunamis and ground shaking during earthquakes, this subsidence – or sinking of the land – could stick around for decades, even centuries. She emphasized that this could completely transform coastal communities in the region.
Unlike other coastal areas dealing with rising sea levels, the Pacific Northwest has been somewhat spared due to its unique geology. The area is a subduction zone, where oceanic plates slide under continental plates. The last major earthquake in this Cascadia subduction zone was way back in 1700. Since then, the coastline has been slowly rising, outpacing sea-level rise caused by climate change in many places. But, as Dura pointed out, climate change is catching up and by 2030, sea levels are expected to rise faster than the uplift in the Cascadia region.
Geologists have known for a while that a big earthquake in the Cascadia region could cause the coast to drop. This sinking has happened before in major subduction-zone earthquakes, like the one in Chile back in 1960 or the devastating 2004 earthquake and tsunami in Indonesia. Evidence from the 1700 quake in the Pacific Northwest shows that forests turned into mudflats after sinking below sea level.
But what sets this new study apart is that it looks at how this sinking, or subsidence, would interact with rising sea levels due to climate change. Dura and her team compared the land that would end up in the FEMA 100-year floodplain if a magnitude 8 earthquake were to hit today versus in 2100 when sea levels are projected to rise even more. And the results are pretty alarming. In the worst-case scenario of 6.6 feet of subsidence, the floodplain area would increase significantly, putting more residents at risk of flooding.
The expanded floodplain also includes critical infrastructure like wastewater treatment plants, electrical substations, and airports. All of these areas could be impacted not only by a tsunami following a major earthquake but also by continued flooding in the aftermath. The study suggests that having these expanded floodplain maps could help emergency managers and city planners prepare for the worst-case scenario.
The research findings were published in the journal PNAS on April 28. Stephanie Pappas, a writer for Live Science, covered this story. She delves into various topics like geoscience, archaeology, and human behavior. Stephanie is a freelancer based in Denver, Colorado, and her work can be found in publications like Scientific American and The Monitor. She holds a bachelor’s degree in psychology from the University of South Carolina and a graduate certificate in science communication from the University of California, Santa Cruz.
And that’s a wrap on this mind-blowing study about earthquakes, subsidence, and rising sea levels in the Pacific Northwest. It’s definitely something to keep an eye on for the future.
