Clark, Cowlitz, Lewis, Klickitat and Skamania counties are participating in the Great Washington ShakeOut on Thursday, according to the Washington State Patrol.
A test alert of the ShakeAlert earthquake warning system will be sent at 10:20 a.m. to mobile devices with the MyShake app installed. All tsunami sirens will also go off at that time, so people know what they will sound like in an actual emergency, the State Patrol said.
People inside buildings are encouraged to drop, cover and hold on, and then practice tsunami evacuation routes.
