PORTLAND, Ore. -- New earthquake predictions for Oregon highlight new risks for Portland and a possible disaster more powerful that scientists had thought.

This week the U.S. Geological Survey published new nationwide hazard maps. One of the changes centered on the Cascadia Subduction Zone off the Oregon Coast.

In the past scientists believed there would likely be several smaller earthquakes along that fault line. But this new research shows evidence the entire subduction zone could shake all at once resulting in a magnitude nine earthquake.

“On average the whole zone will rupture every once every 500 years, but it now seems a little bit more likely that the larger type earthquake is what we have to be ready for,” explained Evelyn Roeloffs.

More: USGS quake maps, info

Roeloffs is a geophysicist with the U.S. Geological Survey in Vancouver. She says the new maps also show the potential for an earthquake beneath Portland.

Experts believe it would be similar to the Nisqually earthquake that hit the Seattle area back in 2001. That was a 6.8 quake that caused more than two billion dollars in damage.

Scientists say the last massive earthquake to hit the Pacific Northwest happened about 300 years ago.

They say it could be hundreds of years before another one hits our area. But these new studies remind all of us, we need to be prepared for one now.

Also: 'Swarm' of quakes off Ore. coast

Background: Portland quake recalls "Spring Break Quake"