WASHINGTON (Reuters) – Scientists have underestimated the potential for a giant quake and tsunami that could swamp much the U.S. northwest and Canadian west coasts, British and U.S. researchers said on Monday.

Geological evidence suggests there have been earthquakes in the past that were even stronger than a magnitude 9.2 quake -- the second-biggest ever recorded -- which caused a 42-foot-high (12-meter-high) tsunami in the Gulf of Alaska in 1964, they said.

"Our data indicate that two major earthquakes have struck Alaska in the last 1,500 years and our findings show that a bigger earthquake and a more destructive tsunami than the 1964 event are possible in the future," Ian Shennan, a professor of geography at Britain's Durham University, who led the study, said in a statement.

"The region has been hit by large, single-event earthquakes and tsunamis before, and our evidence indicates that multiple and more extensive ruptures can happen."

For their study, the teams at Durham, the University of Utah and Plafker Geohazard Consultants studied subsoil samples and sediments from the Alaskan coast and found evidence of major disasters 900 years ago and 1,500 years ago.

Writing in the journal Quaternary Science Reviews, they said the underlying geology of the region shows a very large and widespread quake is possible.

"The 1964 tsunami spread southward along the coast of British Columbia, Washington, Oregon and into northern California," University of Utah geologist Ron Bruhn said in a statement.

"Our work suggests that the northeastern end of the Aleutian megathrust has greater earthquake magnitude and tsunami potential than previously thought," he added.

Tsunami warning systems have been installed along the U.S. west coast and around Hawaii and experts are working to improve them since a quake off Indonesia in 2004 caused a monster tsunami that killed 230,000 people and devastated coastlines from Thailand to Sri Lanka.

(Editing by Sandra Maler)