Mega Tsunami Threat in Three U.S. Regions, Experts Warn. Scientists warn that a devastating “mega tsunami” is a real possibility in parts of the U.S., especially Northern California, Oregon, Washington, Alaska, and Hawaii.

The main threat comes from the Cascadia Subduction Zone, a massive fault line stretching from Vancouver Island to Northern California. A new study from Virginia Tech, published in the Proceedings of the National Academy of Sciences, found that a major earthquake here could cause coastal land to sink by up to 6.5 feet, greatly expanding flood zones.

“There’s a 15% chance of an 8.0+ magnitude earthquake in the next 50 years,” said lead researcher Tina Dura. Combined with sea level rise, this could overwhelm coastal towns and delay recovery efforts. Unlike normal waves, mega tsunamis can reach hundreds of feet high and move rapidly inland, triggered by earthquakes, landslides, or volcanic eruptions.

Alaska is at risk due to glacier melt causing landslides, while Hawaii faces danger from collapsing volcanoes. A 1,000-foot wave once hit the island of Lanai around 105,000 years ago. These threats fall within the Ring of Fire, a seismically active zone around the Pacific Ocean. The last major Cascadia quake occurred in 1700, making another long overdue.

What to do?
While you can’t prevent a tsunami, you can prepare: know evacuation routes, follow alerts, and have a family emergency plan. Experts say it’s not a question of if, but when.