ShakeAlert sounds off at 3 a.m. jolting Californians awake likely by mistake

Many Californians were jolted awake Thursday at 3:20 a.m. – and then never went back to sleep – after a test of the earthquake alert phone warning system went off at that pre-dawn hour, likely by mistake.

ShakeAlert, the warning system that feeds the MyShake app, acknowledged on social media that there was "likely a mix-up between time zones set in the test alert system." 

The system also acknowledged that 3 a.m. is not an ideal time to wake up – especially a day after the same system issued a 5.7-magnitude earthquake rocked the Sacramento area, before the US Geological Survey quickly downgraded that quake to a 4.1. 

"You might have gotten a test alert from the @MyShakeApp early today," ShakeAlert posted. "We acknowledge that no one wants to get a test message this early and we are working with our #ShakeAlert techical partner to determine what happened."

ShakeAlert was preparing the public for the Great ShakeOut earthquake drill that is supposed to happen at 10:19 a.m. PST on Thursday (a much more reasonable hour).