How fast did the earthquake alert go out?

How fast did the earthquake alert go out?

Bay Area earthquake came with early warning for 2.1 million ShakeAlert app users

Published 10:00 pm, Wednesday, April 1, 2011

The big question for the Bay Area after Tuesday’s earthquake: how fast did the warning go out?

The answer: “Faster than you can say ‘Earthquake!’”

The Bay Area ShakeAlert app went live Tuesday morning and by 3:24 that afternoon, it registered at 5.0. By 8:24, the alert was at 4.5 and by 10:24, it was at 3.0. The earliest possible time for earthquake, said the quake’s geologist, is about 4.7 or 4.8 on the Richter scale.

The San Francisco Bay Area has a large population with mobile devices that can get alerts.

“The number of people who have mobile devices, you can imagine the number of people that have smartphones,” said David Fries, an associate professor at UC Berkeley’s Geophysical Laboratory.

“So, we’ll call them ‘smartphone users.’”

By the afternoon, about 6 million people, or one in five Americans, had downloaded ShakeAlert, which was designed to send out earthquake alarms to mobile devices when their proximity sensors detected an earthquake.

Fries said they know of no way to send an alert to all people with the ShakeAlert app but would be willing to try.

As for the earthquake’s magnitude, Fries said that the geologists at the U.S. Geological Survey have determined the fault line through which the quake originated is near 9.0.

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