SALEM, Ore. (AP) – An early warning system for earthquakes has launched in Oregon on the 10th anniversary of the devastating quake and tsunami in Japan.

California already has the system, and Washington state joins it in May to complete coverage of the West Coast.

It’s particularly important in the Pacific Northwest because experts say the “big one” is coming.

The ShakeAlert system is operated by the U.S. Geological Survey uses seismographic sensors to detect significant earthquakes quickly so alerts reach smartphones and people can seek cover before the shaking starts.

Earthquakes in the zone extending from the ocean off Northern California to Canada’s Vancouver Island are among the world’s biggest.

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