More than 3 million people were notified by phone early Tuesday of a 6.4 magnitude earthquake that shook Northern California.
Depending on their distance from the quake's epicenter — which was about 7.5 miles southwest of Ferndale — many residents were informed of the coming tremors before the shaking began, according to Robert de Groot, part of the U.S. Geological Survey's ShakeAlert operations team.
About 270,000 users of the MyShake app, which is funded by the California Governor's Office of Emergency Services, were notified of the earthquake. Most of the 3 million who were notified through Google are Android users who have the alerts preprogrammed into their phone operating system, de Groot said.
The alerts gave users up to 20 seconds to prepare for the earthquake, de Groot said.
"I believe it may be the actual biggest event that we've had (for the system) so far," he said. "The system is doing exactly what it should be. This is actually a really big success for us."
It takes the ShakeAlert operations team time to detect the event using seismometers that pick up the earthquake as it reaches the surface, then informs a processing center that takes the info and produces it into a data package that can be turned into user-friendly alerts.
People with iPhones may have received alerts even if they do not have an earthquake-detecting app. They could be notified by a Wireless Emergency Alerts system push notification, which is similar to an Amber Alert, de Groot said.
People who got the alerts ranged from those already experiencing the shaking to some who didn't feel the quake at all.
"Thank goodness for shake alert! I'd have fainted otherwise! 8+ second warning of severe shaking," said one Twitter user.
Others complained they were notified despite being out of the quake's range.
"Scared the heck outta my wife! Glad to know the notification works, but I wish there was a way to modify the location range a bit more. Now I'm trying to fall back asleep," another Twitter user said.
De Groot said the alert system must balance unnecessary notifications for those outside an earthquake's range with making sure as many residents as possible who could be affected receive a notification.
The number of people notified exceeded the 2.1 million earthquake alerts sent in October when a magnitude 5.1 earthquake struck under the mountains of San Jose.
There are many apps that can deliver alerts in California triggered by the USGS ShakeAlert system: MyShake, QuakeAlertUSA and ShakeReadySD, an app developed for San Diego County but that works statewide.
———
