HUMBOLDT COUNTY, Calif. — The Proceedings of the National Academy of Sciences (PNAS) recently released a study titled ‘Increased flood exposure in the Pacific Northwest following earthquake-driven subsidence and sea-level rise,’ which focused on earthquakes on the Pacific Northwest’s coast.
This will take place along the Washington, Oregon and northern California coasts, due to the next Cascadia subduction zone earthquake, which could cause up to two meters of sudden coastal subsidence, dramatically raising sea level, expanding floodplains and increasing the flood risk to local communities.
Over a dozen researchers participated in the study, including Harvey Kelsey, a Cal Poly Humboldt research associate who describes a portion of it.
“This part of the coast is subjected to earthquakes that are called subduction zone earthquakes, and it is because the shore plate, the oceanic plate, is being tucked underneath the Continental plate, the North America plate,’ said Kelsey.
Kelsey says plate tucking is a continuous process, but it’s regulated by friction. Sometimes, the plate can become stuck or move abruptly. The movement of the underlying plate over the overlying continental plate causes earthquakes, which are caused by subduction zone earthquakes.
“On average, they occur every 300 to 800 years, which is a pretty broad guesstimate of when they occur, but that’s the nature of earthquakes,” said Kelsey.
He says the last subduction zone earthquake was about 300 years ago in Japan, but the earthquake is just one concerning issue. Kelsey also says researchers predict a gradual sea level rise in the next 100 years and another rapid rise due to the subduction zone earthquake.
“For instance, in the next hundred years, the sea level is expected to increase in general on these coastlines by one and a half to two and a half feet, that is a significant rise in sea level,” said Kelsey.
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