During the 10 o'clock hour on October 17, millions of Californians will take part in a statewide earthquake preparedness drill, which state leaders say is part of the largest such drill in the world. The "Great California ShakeOut," as the annual drill is called, takes place this year on the 35th anniversary of the Loma Prieta earthquake, one of the deadliest and most destructive in the state's history. What causes earthquakes in California? The California Governor's Office of Emergency Services asks all of the state's nearly 40 million residents to participate in the drill and to be ready in case of a strong quake in the future. Here's what Californians need to know about the drill. When is the California earthquake drill? The drill will be at 10:17 a.m. on Thursday, coinciding with the numerical date, 10-17-2024. The drill has been done since 2008, often having the time and date coincide. Since then, other states and countries also take part in the drill or organize their own. California’s largest earthquakes of the 21st century What should I do during the drill — or a real quake? CalOES says that a short, three-phrase message will keep you safe: Drop, Cover and Hold On. These steps signify that you should get on your hands and knees to avoid being knocked down, move under a table or desk while covering the back of your head with one arm and hand to protect from debris and use the other arm and hand to hold on to the furniture's legs or something sturdy. People in wheelchairs should follow a similar three-phrase message: Lock, Cover and Hold On. This is how to prepare for and respond to an earthquake These steps signify to lock the wheels in place, hold your hands above your head, and brace yourself until the shaking stops. What about the earthquake phone alert? CalOES and UC Berkeley operate the MyShake App, which is an early warning system that provides warnings up to 35 seconds before a quake hits, the agency said. Which California landmarks are at risk from a massive earthquake? If your cell phone is set up to receive emergency alerts, you may also receive one at 10:17 a.m. that will display a message saying that it is a test of the emergency alert system. In 2023, many phones received the test alert hours earlier due to what officials said was a mixup in time zones, and while the state was getting its messaging out about the drill, a real quake happened in the California Delta region one day before the test. What other states or countries participate? The international ShakeOut drills are conducted in nearly 20 states and U.S. Territories, along with several Canadian provinces and other countries, although a few of these places have the drill at different times and dates.