Scientists Reveal Hidden Earthquake Threat Lurking Beneath CA's Coastline

CALIFORNIA — The Golden State's next exceptionally large temblor of 7.7 or larger along a certain major fault could cause land along the coast to permanently sink, leaving communities vulnerable to catastrophic flooding, a new study warns.

And that’s on top of the tens of thousands of deaths and widespread infrastructure devastation a quake of that size could bring to the Pacific Coast.

Authors of the study, which was published on April 28 in the scientific journal Proceedings of the National Academy of Sciences (PNAS), are urging state officials and local governments to begin preparing now.

The Fault's Next Megaquake Would Sink Parts Of Coastal NorCal

Researchers warn that a "megaquake" — an exceptionally large earthquake with a magnitude of 8.0 or higher — along the Cascadia Subduction Zone could cause the ground in some areas to suddenly sink. The Cascadia Subduction Zone is a fault line that stretches from Northern California to British Columbia. This abrupt sinking, known as "sudden coastal subsidence," would immediately raise local sea levels, inundate floodplains and leave entire coastal communities dangerously exposed to flooding.

Researchers examined what impacts would look like during and after a 7.7 to 9.2 magnitude quake along that fault. The last major temblor on the fault took place in 1700.

A large earthquake would likely cause sinking from half a foot to 6 feet along the coastal communities between southern Washington and Humboldt Bay.

The Cascadia Subduction Zone has the potential to unleash massive earthquakes that could rapidly trigger tsunamis if the shifting of the Juan de Fuca plate beneath the North American plate displaces enough water.

In such a scenario, "All the sea level rise you expected by 2300 is going to happen in minutes," Tina Dura, the lead author and an assistant professor in geosciences at Virginia Tech, told the San Francisco Chronicle.

Dura also warned that a quake along that fault could trigger a tsunami comparable to Japan's deadly 2011 tsunami or the one that killed hundreds of thousands in Sumatra in 2004.

Previous Disaster Simulations Underestimated The Risk

In disaster simulations conducted in 2016 and 2022, officials said that a magnitude 9 Cascadia earthquake could cause catastrophic damage across the Pacific Northwest. The megaquake could be catastrophic, causing over 30,000 deaths, wiping out thousands of bridges, and severely damaging or destroying much of the coastal infrastructure. That includes most roads, fire stations, schools, and ports near the coast, with damages estimated to exceed $81 billion.

But what those earlier scenarios didn’t fully account for, according to the new study, is how the ground itself could sink during the quake — and stay that way for decades or even centuries. That long-term subsidence could lead to even more flooding in coastal areas and significantly slow down recovery efforts.

Beyond devastation to infrastructure, the researchers also noted the damaging impacts a megaquake on this fault could have on nature, particularly in coastal estuaries, intertidal wetlands, dunes and beaches.

Dura confirmed with the Chronicle that the Cascadia Region Earthquake Science Center, which is part of the National Science Foundation, has, so far, been able to maintain its federal funding, surviving cuts imposed by the Trump Administration.

But she and her colleagues are worried about staffing cuts at Tsunami Warning Centers.

“This is a massive disaster looming and we already don’t have enough people on it,” she told the newspaper.

SEE ALSO:

>>This Earthquake Fault Could Devastate SoCal: Report

>>The San Andreas Is Overdue For The Big One, And This Might Be Why

>>Little-Known Bay Area Fault Could Trigger The Next Big One

>>Are You Living on a Fault Line?