Millions of people across California will take part in an annual earthquake preparedness drill.
Now in its fourth year, school children and office workers will practice basic quake survival skills by diving under their desks and holding onto their desks or chairs. Emergency responders and hospitals will stage search-and-rescue missions and mass casualty exercises.
Some 8 1/2 million people have signed up to participate in Thursday's Great California ShakeOut.
Small earthquakes rattle California every day, but the state has not experienced a metropolitan-wide quake disaster since the 1994 Northridge quake that killed 72 and caused $25 billion in damage to the Los Angeles region.
The annual drill has grown since its inception in 2008 as a Southern California regional exercise.