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In the moments before a 6.2-magnitude earthquake struck the northern California coast on Monday, roughly half a million phones began to buzz. From a report: An early-alert system managed by the US Geological Survey sent warnings out before the ground started to shake, giving residents in the sparsely populated area vital time to take cover. The earthquake brought significant shaking but minimal damage in Humboldt county, about 210 miles north-west of San Francisco, and officials said it was an excellent test of the alert-system. It was the largest magnitude quake that’s occurred since the system, known as ShakeAlert, was officially rolled out across the west coast. “We got some reports from folks that they got up to 10 seconds’ warning before they felt shaking. That’s pretty darn good,” said Robert de Groot, a ShakeAlert coordinator with the USGS.

ShakeAlert issues warnings through a series of agencies and apps including the MyShakeApp, public wireless emergency alert systems, and the Android operating system, powered by Google. A data package is created from information provided by USGS sensors and — within seconds — shows up on phones. Some apps that provide alerts are available to download but even some who didn’t have an app on their phone were notified. Affected individuals are instructed to drop, cover, and hold on. Having extra seconds to do so can save lives. This event provided an opportunity for the scientists and system operators to test and improve ShakeAlert so it will be even better when the next big earthquake strikes. “We can run as many simulations and tests as possible but we are really going to learn the most from real earthquakes,” de Groot said. “It’s giving us the chance to use the system and learn how to do a better job of alerting people.”

Read more of this story at Slashdot.