It’s been hundreds of years since a great earthquake has occurred along the Cascadia subduction zone in the Pacific Northwest, but history shows they pop up every 200 to 800 years. If one does strike soon, researchers believe it could trigger a huge tsunami.
That’s according to a new study recently published in the Proceedings of the National Academy of Sciences journal. Researchers found that a “great earthquake” with a magnitude of more than 8.0 has not occurred in the Cascadia subduction zone – part of the “Ring of Fire” where the Pacific plate meets another tectonic plate – since 1700.
In a subduction zone like Cascadia, tectonic plates slide beneath each other, causing an uplift of one plate and pressure between the plates that builds over centuries. If the upper plate becomes “unstuck” it creates an earthquake, as well as an upward water surge that results in a tsunami.
“While the shaking is occurring the land is dropping, and, depending on tidal conditions, low-lying areas may experience immediate flooding,” said a press release from Virginia Tech regarding the recent research. “Within 15 to 20 minutes the tsunami hits with further flooding. The entire process takes no longer than 30 minutes, and multiple tsunami waves may occur over one to two hours.”
Flood risks related to a powerful earthquake could “significantly increase flood risks in the Pacific Northwest, impacting thousands of residents and properties in northern California, Oregon, and Washington,” the press release also said. Around 1.5 to 6.5 feet of land sank along the coastline when the last earthquake rumbled through the region.
Tina Dura, lead author of the study and assistant professor of geosciences in the College of Science, explained that coastal floodplain is expected to expand in the wake of a Cascadia earthquake. However, it isn’t clear just how much. Another thing that is unclear is when the quake might hit. It could hit tomorrow, or it could hit centuries from now.
“Because the timing of the next large earthquake is uncertain, the team modeled the impacts of an earthquake striking today or in 2100, when climate-driven sea-level rise will further amplify the impacts of earthquake-driven subsidence,” said the press release.
A Pacific Northwest earthquake and tsunami might look a bit like natural disaster that have hit other parts of the world. For example, around four years ago, an 8.2-magnitude earthquake hit in the area around Perryville, Alaska, prompting a tsunami alert. Last December, a 7.0 magnitude earthquake struck off the coast of Northern California, prompting a tsunami warning.
According to The Independent, the Cascadia research indicates that an earthquake there would produce a “mega-tsunami” event.
While a big earthquake could result in a big tsunami, the International Tsunami Information Center noted that, as of 2024 no “mega-tsunami” events have ever been recorded in history in the Atlantic or Pacific oceans. One place where a mega-tsunami has occurred is an East Greenland fjord. There, a mountaintop that collapsed into the sea triggered the 650-ft. tall tsunami, per the Scripps Institution of Geography at UC San Diego.