BART, students practice the Great Shake Out earthquake drill

MILLBRAE, Calif. - Today marks the Great California Shake-Out. 

At 10:19 a.m., residents across California, Oregon, and Washington actively participated in an earthquake drill.

That drill included BART, when trains slowed down to 27 miles per hour, then briefly paused before an announcement. 

From public transit systems to workplaces and classrooms across the West Coast, at precisely 10:19 a.m., people were reminded to "drop, cover, and hold on," mimicking the actions they would take during an actual seismic event.

"When we're in our classroom, we protect ourselves by putting our hands behind our neck and going under our desks," 6th-grader Andrew Amoroso said of his classroom drill.

"It's a great idea, especially for the kids to know how to handle themselves during an earthquake," said Andrew’s mother, Abby Amoroso of Half Moon Bay. "As a parent, we're not always present when it happens."

The Great Shake-Out also serves as a reminder to prepare for an earthquake before it strikes. This involves having essential supplies and a well-thought-out plan in place.

"We have an emergency kit, and we've established a meeting point in case of an emergency," said Eileen Ho of Millbrae. 

She was in elementary school during the 1989 Loma Prieta earthquake, which she said "scared the crap out of me," and inspired her afterward to always be prepared for the next big earthquake.

Some My Shake App users got a startling wake-up call at 3 a.m. 

San Francisco Fire Capt. Justin Schorr was one of them. 

"We did receive a surprise shake alert," he said. "One should never dismiss it as a mere drill and always check what's happening." 

Shorr said the accidental alert that went out overnight should be taken in stride and serve as a warning to always be prepared.

In a somewhat apologetic tweet, the U.S. Geological Survey stated, "We acknowledge that no one wants to receive a test message this early," and later provided an explanation to KTVU about what happened.

"There was a minor mix-up with the time zone," said Robert de Groot, a member of the USGS Shake Alert Operations Team. "The intended alert delivery time was supposed to be 10:19 a.m., distributed to all three states."

However, an accidental input of 10:19 Universal Time led to an unsettling wake-up call at 3 a.m. Pacific time for millions of MyShake users in California, Oregon, and Washington.

"One thing I want to assure people is that the shake alert system is in a constant state of improvement. Incidents like this have been addressed," de Groot said.

De Groot encouraged people to keep the My Shake app on their phones, despite the mix-up. 

Emergency responders like Schorr agree having a few seconds of notice before an actual earthquake can help you protect yourself and your family.