Experts Warn: 'Big One' Earthquake Could Submerge West Coast

The next major Pacific Northwest earthquake could cause coastal land to sink by up to 6.5 feet in a matter of minutes — and continue to sink for decades.

Researchers at Virginia Tech University say a magnitude 8.0 tremor on the Cascadia subduction zone fault and rising sea levels could significantly increase flood risks for thousands of residents in the region by expanding floodplains by 116 square miles. Floodplains are areas of land next to rivers or streams that flood when water levels rise.

“The expansion of the coastal floodplain following a Cascadia subduction zone earthquake has not been previously quantified, and the impacts to land use could significantly increase the timeline to recovery,” Tina Dura, an assistant professor of geosciences, said in a statement .

Dura is the principal author of the earthquake study that was released on Thursday in the journal. Proceedings of the National Academy of Sciences .

The most severe effects would occur in southern Washington, northern Oregon, and northern California.

To reach their conclusions, Dura and her team generated tens of thousands of earthquake models to help estimate the potential range of the sinking. They then quantified the expansion of the floodplain at 24 different communities and estuaries in the area of the fault.

They assessed the models based on the effects of an earthquake happening now and how one might unfold in 2100. By that time, climate change is anticipated to be well underway. raise sea levels by as much as four feet .

Should the "Big One" occur today, an extra 14,350 inhabitants, 22,500 buildings, and 777 miles of roads would be included in the area prone to flooding after the earthquake.

This impact would extend to hospitals, state-funded schools, an electrical substation, waste management sites, police and fire stations, along with five airports. Agricultural lands would suffer significant financial losses due to flooding rendering the soil unsuitable for cultivation.

Furthermore, coastal estuaries and wetlands — vital for combating climate change — would suffer erosion, affecting the ecosystems they sustain. The study cautions that these ecosystems might not be able to recuperate.

Significantly, an earthquake of such seismic strength has not taken place along the Cascadia subduction zone since January 26, 1700.

Reviewing data spanning the past 7,000 years reveals that approximately 11 major earthquakes occurred every 200 to 800 years in the Pacific Northwest. The most recent quake caused parts of the coastland to drop by 1.5 to 6.5 feet directly afterward.

Cascadia is a distinctive region. Though not densely populated, nearly every estuary hosts a community, and they're all within the subsidence zone," stated Dura. "In my opinion, this area might experience more significant effects from subsidence compared to what we've seen during other major seismic events globally.

A major earthquake in the Pacific Northwest region could generate tsunami waves up to 40 feet tall, and residents were advised to ready themselves, Dura stated The Washington Post .

You've got the tsunami evacuation signs, but they appear more as a gimmick rather than something genuinely important," Dura commented. "People really should take this seriously.

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