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Are you prepared ... for a tsunami?

Tsunami Hazard Zone sign on California coast.
Tsunami Hazard Zone sign on California coast.
Cal OES/Flickr Creative Commons

Think of a disaster striking California and most of us think earthquakes. But there's more than 34,000 miles of coastline. If you didn't know the state is just as vulnerable to tsunamis, well, now you do. This week is California Tsunami Preparedness Week, and today the state's Office of Emergency Services will run a test of our emergency response system. Tsunami Program Officer Kevin Miller explained the risk.

The most likely causes of tsunamis in California

A tsunami is in most cases caused by a large earthquake under the ocean. It's not necessarily the type of earthquakes we have directly in California. Our tsunamis come from far away, from areas where we have subduction zone earthquakes which will move the ocean floor. Places like off the Aleutian Islands  in Alaska and Japan and off of South America and Chile.

Tsunamis travel as fast as a jet

Generally, they travel about 500 mph in the open ocean, about as fast as a jet. They slow down to 30 to 40 mph once they reach the coast. From Alaska, it would take about five hours to reach Southern California from Japan. We had an event in 2011 that impacted our coast, and it took nine to ten hours to reach us.

Should Southern Californians worry

It sounds like we have a lot of time to react, but we have hundreds of thousands of people, sometimes millions of people at the coast. Think of a 4th of July weekend and the amount of time it takes to leave the beach on a day like that. That's the kind of thing that keeps emergency managers up at night.

The history of tsunami strikes in California

They are potentially high consequence but low probability events. We've had six in the last nine years that have raised alert levels. They typically are not something that causes inundation and damage. In 2011, the Japan earthquake and tsunami caused up to $100 million in damage to coastal facilities in California and that one still did not cause inundation of dry land. In 1964, one of the biggest earthquakes in history in Alaska sent a tsunami to Crescent City and killed 11 people in that city.

How to protect yourself from a tsunami

Walking away from the coast to high ground. That's basically all you need to do to protect yourself.