Associated Incidents
The United States Geological Survey said on Thursday its automatic earthquake detection system had erroneously sent out a report earlier in the day that a 5.9 magnitude temblor had struck in Nevada, saying it was likely the first time the USGS had issued a quake report that was completely bogus.
Yaareb Altaweel, a geophysicist with the survey's National Earthquake Information Center in Golden, Colorado, said the USGS was still trying to understand why its automatic ShakeAlert early warning system sent out the erroneous alert of a quake centered near Dayton, Nevada.
The report prompted cell phones in the San Francisco Bay area, some 180 miles away, to buzz with a warning to residents to "DROP! COVER! HOLD ON!," according to a Reuters witness.
"To my knowledge we've never had a false alert like this," Altaweel said. "The system has put out incorrect information on exaggerated magnitude or depth, which was corrected immediately by the on-duty seismologist. I have seen that happen before."
Angie Lux, a project scientist for earthquake early warning at the Berkeley Seismological Laboratory, also said that a false alert of a major quake had never occurred in the past to her knowledge.
Lux did not know what may have triggered the false alert and said it would take some time to understand what happened.
Lux said the cause may have been "noisy triggers," referring to localized noise from natural or human-made sources, such as explosions, construction work, industrial activities, or even large vehicles such as a train or truck. Natural phenomena for such triggers include wind and ocean waves.
Multiple law enforcement agencies in cities and counties near the reported epicenter confirmed they had felt no shaking or any other signs of an earthquake.
A magnitude 5.9 quake typically is strong enough to cause slight property damage and pronounced shaking, according to the Michigan Tech Earthquake Magnitude Scale.