At 10:18 a.m. sharp, millions of people across Southern California hit the ground and ran for cover. At Union Station, downtown commuters held on for 60 seconds bracing for a 7.8-magnitude earthquake that never happened.
The Great Shake Out is the world's largest earthquake preparedness drill meant to get people ready for the big one.
What began as a regional event in Southern California five years ago is now an annual international affair. Schools, stores and Metrolink all took part.
"Every earthquake that our subway has been in, they've come through with flying colors," said Metrolink Chairman Richard Katz. "We have covered as much as we can cover, knowing that earthquakes and Mother Nature have more variables than we can plan for, but we feel very confident that we have a very good, safe system."
Local leaders stressed the importance of not being complacent.
"Hope doesn't save lives - preparation does," said L.A. Mayor Antonio Villaraigosa.
Chris Nance with the California Earthquake Authority emphasized that all components are necessary to be prepared, including emergency supplies, safety kits as well as practicing to drop, cover and hold on.
During a quake, emergency officials want you to drop to the ground, cover your head and neck and hold on to something sturdy.
"We've had people die from trying to run during earthquakes and being thrown, had their head smashed. And so, the first thing we say is drop. Get down to the ground because the Earth's going to put you there anyway," said Dr. Lucy Jones with the U.S. Geological Survey.
In addition to California, Washington, D.C., Maryland, Virginia as well as residents in British Columbia, Italy, Puerto Rico and Guam signed up for the exercise.
Southern California has not experienced a seismic disaster since the 1994 Northridge quake, which killed 72 people and caused $25 billion in damage to the Los Angeles region.