Napa, CA – A new study published in the Proceedings of the National Academy of Sciences on April 28 offers a dire warning for California’s coastal communities. Researchers predict that a major earthquake along the Cascadia Subduction Zone—one of the most dangerous fault lines in North America—could trigger a catastrophic sequence of events, including the permanent sinking of parts of the coastline and significant flooding, leaving communities vulnerable for decades.
The Cascadia Subduction Zone stretches from Northern California to British Columbia and has the potential to produce a “megaquake” of magnitude 8.0 or higher. The last major event along the fault occurred in 1700, but researchers argue that the region is long overdue for another massive tremor. The study reveals that, in addition to the widespread destruction typically expected from such an event—ranging from tens of thousands of deaths to the collapse of infrastructure—parts of the coastline could suddenly sink, a phenomenon known as “sudden coastal subsidence.”
This subsidence would cause a dramatic and immediate rise in sea levels, flooding low-lying coastal areas, and permanently altering the region’s landscape. Coastal communities between Southern Washington and Humboldt Bay, California, could experience land sinking by as much as six feet, according to the study’s findings. With the ground dropping, local sea levels would increase significantly, inundating floodplains and leaving entire communities dangerously exposed to rising waters.
The researchers examined the potential consequences of a quake with a magnitude ranging from 7.7 to 9.2. In such a scenario, the effects would extend far beyond the initial shaking, with lasting consequences on both the environment and human infrastructure. Alongside the ground subsidence, a megaquake along the Cascadia Subduction Zone could also trigger a tsunami comparable to the deadly waves that struck Japan in 2011 or Indonesia in 2004.
According to Dr. Tina Dura, lead author of the study and assistant professor of geosciences at Virginia Tech, the sudden rise in sea levels following such an event would be catastrophic. “All the sea level rise you expected by 2300 is going to happen in minutes,” Dura said in an interview with the San Francisco Chronicle. She further warned that the destruction caused by such a quake would extend beyond urban areas, with devastating impacts on the region’s natural ecosystems, including estuaries, wetlands, and coastal beaches.
The potential for a massive tsunami—triggered by the shifting of the Juan de Fuca plate beneath the North American plate—has long been acknowledged in disaster simulations. These previous simulations, conducted in 2016 and 2022, have focused on the expected loss of life, widespread destruction of infrastructure, and economic costs, which could exceed $81 billion. However, this new study highlights a crucial element that has often been overlooked: the long-term effects of the ground sinking during and after the quake.
While initial destruction from the earthquake would be devastating, the lasting effects of subsidence would make recovery efforts significantly more challenging. Researchers warn that the resulting flooding, combined with the damage to infrastructure, could delay recovery for decades, leaving the region particularly vulnerable to long-term disruption.
Dura and her colleagues have also raised concerns about the federal and state governments’ preparedness for such a catastrophic event. Despite the significant risks posed by the Cascadia Subduction Zone, funding for critical research and emergency preparedness efforts remains under strain. Dura noted that while the Cascadia Region Earthquake Science Center continues to receive federal support, staffing cuts at Tsunami Warning Centers and other emergency response agencies could hinder efforts to adequately respond to the threat.
“This is a massive disaster looming and we already don’t have enough people on it,” Dura emphasized. As coastal communities brace for the possibility of such a disaster, the study’s authors urge state and local governments to prioritize funding for earthquake preparedness and flood mitigation efforts to better protect vulnerable populations.
With a megaquake potentially on the horizon, experts are calling for immediate action. As the study makes clear, the risks are not only high but growing, and now is the time for government officials and local agencies to increase preparedness and invest in the necessary infrastructure to safeguard the Pacific Coast from what could be one of the most destructive natural disasters in modern history.