Experts warn: Three U.S. regions at risk of possible ‘mega-tsunami’

Imagine waking up to the sound of sirens and the ocean moving closer to your neighborhood. While this may sound like something out of a movie, scientists say certain areas along the U.S. West Coast could face that very scenario in the future.

Researchers are paying close attention to a powerful geological feature known as the Cascadia subduction zone, which stretches from Northern California to British Columbia. Experts say this area has the potential to produce a significant earthquake — and possibly a large tsunami event that could affect parts of California, Oregon, Washington, Alaska, and Hawaii.

What Is the Cascadia Subduction Zone?

The Cascadia subduction zone is a major fault line where two tectonic plates meet. When pressure builds along this boundary, it can result in a powerful earthquake. According to a new study published in the Proceedings of the National Academy of Sciences, such an event could also cause land along the coast to sink by up to 6½ feet, increasing the risk of coastal flooding in certain regions.

“The expansion of the coastal floodplain following a Cascadia subduction zone earthquake has not been previously quantified,” said Dr. Tina Dura, a geoscientist at Virginia Tech and lead author of the study. “The impacts to land use could significantly increase the timeline to recovery.”

Understanding the Potential Risk

The U.S. Geological Survey estimates there’s a 15% chance of a magnitude 8.0 or greater earthquake along the Cascadia fault in the next 50 years. While such events are rare, researchers emphasize the importance of being informed and prepared, especially for communities near sea level.

Tsunamis occur when large volumes of water are displaced — often due to underwater earthquakes, landslides, or volcanic activity. These waves travel fast and can rise significantly in height as they approach land.

In the Pacific Northwest, coastal areas — particularly low-lying towns near estuaries — may be at increased risk if land subsidence occurs during a quake, researchers noted.

What About Alaska and Hawaii?

Alaska is also being closely watched due to its frequent seismic activity and unique geography. As glaciers melt, conditions for landslides can increase, which may raise the risk for localized tsunami activity.

In Hawaii, volcanic history plays a role. About 105,000 years ago, scientists believe a section of volcanic terrain collapsed into the ocean, causing a wave that impacted the island of Lanai. While such events are extremely rare, experts monitor Mauna Loa and Kilauea, two of Hawaii’s most active volcanoes, for any signs of major geological change.

All Part of the “Ring of Fire”

These concerns fall within a broader region known as the Ring of Fire — a massive tectonic zone circling the Pacific Ocean known for its active volcanoes and frequent earthquakes. The last major event along the Cascadia fault occurred in 1700, over 300 years ago. Scientists believe the area may be overdue for another large-scale seismic event.

How to Stay Prepared

While scientists can’t predict the exact timing of future earthquakes or tsunami events, emergency preparedness remains key:

Know your area’s evacuation routes
Sign up for local alerts and weather warnings
Keep a family emergency plan in place
Prepare a basic emergency kit with essentials
These simple steps can help communities stay safe and informed.
Living in coastal or earthquake-prone regions always comes with some level of natural risk — but with preparation and awareness, individuals and families can be ready for whatever the future brings.