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.
