California conducted its annual “drop, cover, and hold on” drill to teach citizens how to protect themselves while an earthquake is occurring.

More than 10 million residents of the earthquake-prone state signed up to participate in the 2015 Great California ShakeOut, an event that began in 2008, organizers said. All were to scramble under desks or tables during a simulated temblor at 10:15 a.m.

Los Angeles Mayor Eric Garcetti joined in during radio station KNX’s live “Ask the Mayor” segment. “Things that are falling will kill you,” Garcetti said in urging people to join the drill.

Schools and universities account for most of the participants in the simultaneous disaster drill, organized by the Earthquake Country Alliance, that has spread well beyond California to many other states and countries. In Washington state, U.S. Interior Secretary Sally Jewell participated Thursday in a Great Washington ShakeOut drill in Oso, the site of a deadly landslide last year.

For many, the exercise just consists of dropping and covering under desks as generations of California schoolchildren have done. But the Shakeout is designed to simulate more coordinated and widespread action.

On some school campuses, student act out roles as earthquake victims, as health care professionals assess and treat them, setting up a triage area and assigning them different levels of injuries.

Organizers have carried out similar exercises at train stations and hospitals.

California has small earthquakes daily, such as a cluster occurring this week under cities east of San Francisco. The drill, however, seeks to prepare citizens for the sort of devastating quake the state hasn’t seen in decades.

The last was the 1994 Northridge disaster that killed 60 people and injured more than 7,000 in metropolitan Los Angeles.

In Northern California in 1989, a magnitude-6.9 earthquake in the San Francisco Bay region killed 63 people, injured nearly 3,800 and caused up to $10 billion in damage.

When the first drill was planned in 2008, organizers based it on a scenario of a magnitude-7.8 earthquake on the southern section of the mighty San Andreas Fault, the type of quake that experts say will happen although they can’t say when. An earthquake of that size would cause shaking for nearly two minutes.

Experts said such a quake would inflict vastly more damage than the Northridge quake and cause more than 1,800 deaths and 50,000 injuries.

Drill organizers include the Southern California Earthquake Center, the U.S. Geological Survey and the Governor’s Office of Emergency Services, among others.

(AP)