Environment & Science

Researchers to study threat of tsunamis triggered by underwater landslides

A lifeguard keeps watch for tsunami waves following the 2011 Japanese earthquake.
A lifeguard keeps watch for tsunami waves following the 2011 Japanese earthquake.
David McNew/Getty Images

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A national team of scientists will be taking a closer look at a rare but potentially dangerous type of tsunami this year.

The tsunamis are caused by underwater landslides and can strike with little or no warning and result in large waves reaching nearby shores.

Related: Tsunami Preparedness Week: What LA areas are at risk?

Underwater landslide tsunamis are different from the type of tsunami that occurred this week after the 8.2 magnitude quake in Chile, says USC researcher Patrick Lynett.

He says that kind of tsunami is triggered when a fault on the ocean floor shifts during a quake, displacing tremendous volumes of water and sending them ashore.

Underwater landslide tsunamis happen when a quake or other disturbance causes a cliff on the ocean floor to partially collapse, creating a similar surge of water.

Related: What sort of damage could a West Coast tsunami do?

Lynett says that they don't always originate near the epicenter of a quake and can even be triggered with no quake at all, giving little warning.

"Pretty much our first sign that a landslide-generated tsunami occurred is when we observe it on the coast," he said.

If they occur close to shore, Lynett says residents may have as little as 15 minutes to evacuate to higher ground.

Rick Wilson is a geologist with the California Geological Survey. He says there are several regions in California with the type of underwater topography that is associated with this kind of event.

"Whether it be Monetary Bay or off the coast of the Port of Los Angeles or San Diego, those are areas where we could see these types of landslides that could trigger tsunamis," Wilson said.

Researchers have studied typical tsunamis for decades, but underwater landslide tsunamis are a relatively new area of concern.

Wilson says his team included the threat of this kind of event when mapping tsunami inundation zones in 2009.

But he says there is still a lot we don't understand about them, like how often they occur or what type of quakes can trigger them.

To find the answers, the National Oceanic and Atmospheric Administration is teaming up with the U.S. Geological Survey and FEMA to study landslide tsunamis this summer.