San Franciscans barely had time for a first sip of coffee before their phones started screaming just after 8 AM. today, flashing a stark command to “Drop, Cover and Hold On” for a magnitude 5.9 earthquake reported east of Lake Tahoe. Within minutes, that supposed quake vanished from official seismology feeds, leaving residents wondering whether they had just dodged a disaster or been duped by a glitch.
What Happened
According to the San Francisco Chronicle, the U.S. Geological Survey briefly listed a magnitude 5.9 event about 20 miles east of Lake Tahoe, then removed the listing from its site by 8:23 AM PT. Lyon County did not send any emergency notices, and officials reported no shaking in San Francisco.
Officials Say The Early-Warning System Sent An 'Errant' Message
Paul Earle, director of the USGS National Earthquake Information Center, told SFGATE that the alert was an “errant message from earthquake early warning system” and said the agency is investigating what triggered the bogus notification. The phantom quake briefly showed up on USGS feeds before being deleted.
Why You Got The Alert
The warning went out through ShakeAlert partners, including the MyShake app, which sends early warning alerts within seconds of a magnitude 4.5 or larger earthquake to devices in predicted shaking zones, according to MyShake. Those automated thresholds are designed to reach people who would likely feel light shaking, which is why phones as far away as San Francisco lit up with the notice.
How The System Handles Errors
The USGS explains that preliminary earthquake notices are generated automatically so warnings can go out as fast as possible, and that mistakes can happen. Entries that turn out to be wrong are quickly corrected or deleted while seismologists review the underlying data. The agency’s errata page notes that the trade-off for speed is that some early posts are later removed once experts sort out what actually happened.
Bay Area Reaction
Across the Bay Area, residents reported their phones buzzing in unison and flooded social platforms to ask whether anyone had felt even a hint of shaking. The initial listing indicated a quake centered near Dayton in Lyon County, but local officials did not send mass notices, according to the San Francisco Chronicle, and many people in Reno and the Tahoe region also said they felt nothing at all.
What To Check On Your Phone
If that surprise alert yanked you out of bed or out of your commute, it might be a good time to review your MyShake or device warning settings. Make sure location permissions and background refresh are enabled, set a HomeBase in MyShake if you use it, and keep the app updated so it is not pushed into deep sleep. The MyShake FAQ walks through those settings and explains why you sometimes get notified about quakes that are relatively far away.
The USGS says it is investigating the incident and will release more information when it is available. Initial automated feeds listed the event before it was deleted, as first reported by Reuters. This story will be updated as agencies provide further details.
