Officials investigating false earthquake alert in Northern California and Nevada
On Thursday morning, many people across Northern California and Nevada saw earthquake alerts, warning of a magnitude 5.9 quake near Dayton, Nevada.
The words “Drop! Cover! Hold on!” flashed on phones, warning people to brace for major tremors, only for nothing to happen — no shaking, no earthquake at all.
The warning came from ShakeAlert, the earthquake early-warning system run by the U.S. Geological Survey at the Department of the Interior. The system, which operates in California, Oregon and Washington, is designed to provide advanced notice about earthquakes so people can turn off machinery or get to safe locations before shaking begins.
Within minutes of the alert, officials realized there had been no earthquake, pulled the alert and confirmed on social media it had been a false alarm.
“The earthquake alerts that were delivered at 8:06am are cancelled,” USGS posted on Facebook and other major social platforms shortly after the false warnings were sent. “There was no M5.9 earthquake near Carson City, NV. We are currently looking into why the alerts were issued.”
Robert de Groot, who heads the Shake Alert operations team at USGS, said the automatic detection system detected ground motion and triggered the false alert, but confirmed within minutes that an earthquake had not occurred. He said Shake Alert uses four sensors, rather than one, to mitigate false alerts. In this instance, all four sensors went off.
“The important thing is the shaker Earthquake Early Warning System performed as it was designed in terms of the sensor network, which actually detects the earthquake and the ground motion, de Groot said. “The system was just reacting to the data that that looked and smelled like an earthquake. Something was detected at those sensors.”
The USGS tracks false earthquake alerts on its website, which states that the “faster we release earthquake locations and magnitudes, the more likely it is that the information may be erroneous.” The department lists two false alerts since ShakeAlert’s 2019 launch, both issued in California in 2020. One alert detected seismic activity 200 kilometers away from the where the sensor was located and was unlikely to result in an earthquake. The other was triggered by a 7.5 magnitude earthquake in Russia, which confused the earthquake monitoring system in Northern California.
De Groot said that while Shake Alert has issued more than 170 successful alerts, Thursday’s miscommunication is unlike the others in that it’s the first time the system has issued a false alert using data that was not collected from an actual earthquake that took place. The team is still investigating the source of the trigger.
“Earthquake early warning is done over a very short time period, we’re talking matters of seconds,” de Groot said. “So if you put your hand on your heart couple of heartbeats, that time of two heartbeats or so, about a second, that is all we need to get things moving in the Shake Alert system.”
