LOS ANGELES " Some 5 million Californians promise to duck to the ground and hold on to furniture come 10 a.m. Thursday as if an earthquake just struck.
It's not real " but since earthquakes are a big threat to California, the state is starring in a mock quake disaster drill billed as the largest in U.S. history.
The exercise is based on a hypothetical magnitude-7.8 temblor that ruptures the southern San Andreas Fault " an event that scientists call the feared "Big One." Such a quake would cause 1,800 deaths and $200 billion in damage, researchers estimate.
The state's previous simulated quake catastrophes were smaller in scale. Thursday's drill will involve local governments, emergency responders, schools, hospitals, churches, businesses and residents doing their part.
"We're trying to make it a communal event," said U.S. Geological Survey seismologist Lucy Jones, who helped create the crisis scenario.
California is the most seismically active state in the Lower 48. Earlier this year, the USGS calculated the state faces a 46 percent chance of being hit by a 7.5 or larger quake in the next 30 years with the epicenter likely in Southern California.
The drill coincides with an annual statewide preparedness event put on by the state. Besides rehearsing for natural disasters, the state in the past has responded to simulated terrorist attacks.
For Thursday's drill, the minimum participation calls for people to dive for safety. Firefighters and other emergency responders are staging full-scale exercises complete with search-and-rescue missions and medical triaging of people posing as casualty victims.