For many, that alert came seven hours before it was supposed to, at 3:19 a.m.
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"We were supposed to send the alert at 10:19 a.m. Pacific Time, however, at some point, it seems as though our system sent it at 10:19 UTC time which is kind of a universal time, which is essentially seven hours different here in the Pacific," Angie Lux, PH.D., a Project Scientist for Earthquake Early Warning at the Berkeley Seismological Lab said.
Lux says it seems as though one of the servers was miscalibrated with the wrong time zone.
"We do want to be mindful that people didn't really appreciate the fact that the alert went off in the middle of the night however, as you say, it is a good reminder that the earthquakes can go off at any time," she said. "Now, I'm sure other people are aware as I am that the alerts will break through your do not disturb."
"It's a great opportunity to practice, but it's also to realize that we have an earthquake early warning system in California, Oregon and Washington," USGS Lead Shake Alert Operations Team Robert de Groot said. "So, it's also a chance to practice either dropping, covering and holding on because of shaking, or because of receiving an alert."
MyShake issued a statement on X, formerly known as Twitter, saying:
"The test alert was sent at 3:19 a.m. Pacific Time due to a configuration glitch. We apologize to all of our users and will ensure that this will not occur in the 2024 shakeout drill. The capability of MyShake to deliver realtime alerts for real earthquakes is not affected."
While some were woken up at 3 a.m. and others received the alert on time at 10:19, we were told by dozens of people that they didn't receive an alert at all Thursday.
"I think it has potential, but I didn't get the alert today so I wonder, 'does it really work'?" San Jose's Kathryn Class said.
RELATED: Bay Area expert explains why ShakeAlert overestimated 4.2 magnitude NorCal earthquake
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Unlike the real alert that came during that 4.2 quake in Sacramento County, de Groot told us Thursday's test alert required prior download of the MyShake App.
Errors during the great shakeout have some questioning the early warning system. But de Groot says it's still an important tool in earthquake safety and preparedness.
"Keep your faith in it," de Groot said. "We're making it better every day. It's there to protect people. Our priority is public safety. So, we just want people to understand that this is all being done in the name of keeping people safe."
On Thursday, precisely at 10:19 a.m., BART riders on trains heard a system-wide announcement warning them about an earthquake test alert.
That's when the MyShake app issued a test alert across the state for an earthquake, urging everyone to drop, cover and hold on.
"It's a good moment to reflect on where they will be and what they would do in the event of an earthquake and if you're in the BART system, the best thing for someone to do is to listen for announcements," Jim Allison, a spokesperson for BART said.
BART is one of many organizations participating in the Great California ShakeOut.
As soon as the MyShake alert was triggered, trains automatically slowed down to 27 miles per hour before coming to a brief stop.
This year, BART engineers are also doing a simulated check for damage.
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"Our engineers will divide into inspection teams and they will head out to all 50 stations, they're going to be looking at things like the walkways, the aerial tracks and just taking an inventory of everything that could be damaged in a major earthquake," Allison said.
This is something MyShake App users should already be familiar with after the app alerted people across the Bay Area to a 5.7 quake in Sacramento County on Wednesday, although it was actually just a 4.2 magnitude.
"ShakeAlert is operating very very quickly, early warning is not a prediction, it's saying an earthquake has happened and we are going to let you know that the shaking is about to reach you," Lux said.
According to shakeout.org, more than 10.1 million people across the state were registered to participate in the Great California Shakeout.
Click here for the latest stories and videos about earthquakes here in the Bay Area and around the world, and click here for more information on disaster preparedness.
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